Mellerowicz, Ewa - Wood Matrix Polysaccharides: Biosynthesis and Modification

@article{bernacki_biotechnological_2023,
	title = {Biotechnological {Potential} of the {Stress} {Response} and {Plant} {Cell} {Death} {Regulators} {Proteins} in the {Biofuel} {Industry}},
	volume = {12},
	copyright = {http://creativecommons.org/licenses/by/3.0/},
	issn = {2073-4409},
	url = {https://www.mdpi.com/2073-4409/12/16/2018},
	doi = {10.3390/cells12162018},
	abstract = {Production of biofuel from lignocellulosic biomass is relatively low due to the limited knowledge about natural cell wall loosening and cellulolytic processes in plants. Industrial separation of cellulose fiber mass from lignin, its saccharification and alcoholic fermentation is still cost-ineffective and environmentally unfriendly. Assuming that the green transformation is inevitable and that new sources of raw materials for biofuels are needed, we decided to study cell death—a natural process occurring in plants in the context of reducing the recalcitrance of lignocellulose for the production of second-generation bioethanol. “Members of the enzyme families responsible for lysigenous aerenchyma formation were identified during the root hypoxia stress in Arabidopsis thaliana cell death mutants. The cell death regulatory genes, LESION SIMULATING DISEASE 1 (LSD1), PHYTOALEXIN DEFICIENT 4 (PAD4) and ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) conditionally regulate the cell wall when suppressed in transgenic aspen. During four years of growth in the field, the following effects were observed: lignin content was reduced, the cellulose fiber polymerization degree increased and the growth itself was unaffected. The wood of transgenic trees was more efficient as a substrate for saccharification, alcoholic fermentation and bioethanol production. The presented results may trigger the development of novel biotechnologies in the biofuel industry.},
	language = {en},
	number = {16},
	urldate = {2023-08-31},
	journal = {Cells},
	author = {Bernacki, Maciej Jerzy and Mielecki, Jakub and Antczak, Andrzej and Drożdżek, Michał and Witoń, Damian and Dąbrowska-Bronk, Joanna and Gawroński, Piotr and Burdiak, Paweł and Marchwicka, Monika and Rusaczonek, Anna and Dąbkowska-Susfał, Katarzyna and Strobel, Wacław Roman and Mellerowicz, Ewa J. and Zawadzki, Janusz and Szechyńska-Hebda, Magdalena and Karpiński, Stanisław},
	month = aug,
	year = {2023},
	note = {Number: 16
Publisher: Multidisciplinary Digital Publishing Institute},
	keywords = {bioethanol, biofuels, cell death, cell wall, lignin, poplar, scarification},
	pages = {2018},
}

Production of biofuel from lignocellulosic biomass is relatively low due to the limited knowledge about natural cell wall loosening and cellulolytic processes in plants. Industrial separation of cellulose fiber mass from lignin, its saccharification and alcoholic fermentation is still cost-ineffective and environmentally unfriendly. Assuming that the green transformation is inevitable and that new sources of raw materials for biofuels are needed, we decided to study cell death—a natural process occurring in plants in the context of reducing the recalcitrance of lignocellulose for the production of second-generation bioethanol. “Members of the enzyme families responsible for lysigenous aerenchyma formation were identified during the root hypoxia stress in Arabidopsis thaliana cell death mutants. The cell death regulatory genes, LESION SIMULATING DISEASE 1 (LSD1), PHYTOALEXIN DEFICIENT 4 (PAD4) and ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) conditionally regulate the cell wall when suppressed in transgenic aspen. During four years of growth in the field, the following effects were observed: lignin content was reduced, the cellulose fiber polymerization degree increased and the growth itself was unaffected. The wood of transgenic trees was more efficient as a substrate for saccharification, alcoholic fermentation and bioethanol production. The presented results may trigger the development of novel biotechnologies in the biofuel industry.

@article{donev_field_2023,
	title = ,
	volume = {21},
	issn = {1467-7652},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/pbi.14012},
	doi = {10.1111/pbi.14012},
	abstract = {Trees constitute promising renewable feedstocks for biorefinery using biochemical conversion, but their recalcitrance restricts their attractiveness for the industry. To obtain trees with reduced recalcitrance, large-scale genetic engineering experiments were performed in hybrid aspen blindly targeting genes expressed during wood formation and 32 lines representing seven constructs were selected for characterization in the field. Here we report phenotypes of five-year old trees considering 49 traits related to growth and wood properties. The best performing construct considering growth and glucose yield in saccharification with acid pretreatment had suppressed expression of the gene encoding an uncharacterized 2-oxoglutarate-dependent dioxygenase (2OGD). It showed minor changes in wood chemistry but increased nanoporosity and glucose conversion. Suppressed levels of SUCROSE SYNTHASE, (SuSy), CINNAMATE 4-HYDROXYLASE (C4H) and increased levels of GTPase activating protein for ADP-ribosylation factor ZAC led to significant growth reductions and anatomical abnormalities. However, C4H and SuSy constructs greatly improved glucose yields in saccharification without and with pretreatment, respectively. Traits associated with high glucose yields were different for saccharification with and without pretreatment. While carbohydrates, phenolics and tension wood contents positively impacted the yields without pretreatment and growth, lignin content and S/G ratio were negative factors, the yields with pretreatment positively correlated with S lignin and negatively with carbohydrate contents. The genotypes with high glucose yields had increased nanoporosity and mGlcA/Xyl ratio, and some had shorter polymers extractable with subcritical water compared to wild-type. The pilot-scale industrial-like pretreatment of best-performing 2OGD construct confirmed its superior sugar yields, supporting our strategy.},
	language = {en},
	number = {5},
	urldate = {2023-04-21},
	journal = {Plant Biotechnology Journal},
	author = {Donev, Evgeniy N. and Derba-Maceluch, Marta and Yassin, Zakiya and Gandla, Madhavi Latha and Pramod, Sivan and Heinonen, Emilia and Kumar, Vikash and Scheepers, Gerhard and Vilaplana, Francisco and Johansson, Ulf and Hertzberg, Magnus and Sundberg, Björn and Winestrand, Sandra and Hörnberg, Andreas and Alriksson, Björn and Jönsson, Leif J. and Mellerowicz, Ewa J.},
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/pbi.14012},
	keywords = {BET analysis, Populus, SilviScan, enzymatic saccharification, field trial, secondary cell wall, subcritical water extraction, transgenic Populus, transgenic trees, wood quality},
	pages = {1005--1021},
}

Trees constitute promising renewable feedstocks for biorefinery using biochemical conversion, but their recalcitrance restricts their attractiveness for the industry. To obtain trees with reduced recalcitrance, large-scale genetic engineering experiments were performed in hybrid aspen blindly targeting genes expressed during wood formation and 32 lines representing seven constructs were selected for characterization in the field. Here we report phenotypes of five-year old trees considering 49 traits related to growth and wood properties. The best performing construct considering growth and glucose yield in saccharification with acid pretreatment had suppressed expression of the gene encoding an uncharacterized 2-oxoglutarate-dependent dioxygenase (2OGD). It showed minor changes in wood chemistry but increased nanoporosity and glucose conversion. Suppressed levels of SUCROSE SYNTHASE, (SuSy), CINNAMATE 4-HYDROXYLASE (C4H) and increased levels of GTPase activating protein for ADP-ribosylation factor ZAC led to significant growth reductions and anatomical abnormalities. However, C4H and SuSy constructs greatly improved glucose yields in saccharification without and with pretreatment, respectively. Traits associated with high glucose yields were different for saccharification with and without pretreatment. While carbohydrates, phenolics and tension wood contents positively impacted the yields without pretreatment and growth, lignin content and S/G ratio were negative factors, the yields with pretreatment positively correlated with S lignin and negatively with carbohydrate contents. The genotypes with high glucose yields had increased nanoporosity and mGlcA/Xyl ratio, and some had shorter polymers extractable with subcritical water compared to wild-type. The pilot-scale industrial-like pretreatment of best-performing 2OGD construct confirmed its superior sugar yields, supporting our strategy.

@article{urbancsok_flexure_2023,
	title = {Flexure wood formation via growth reprogramming in hybrid aspen involves jasmonates and polyamines and transcriptional changes resembling tension wood development},
	copyright = {New Phytologist© 2023 The Authors New Phytologist © 2023 New Phytologist Foundation},
	issn = {1469-8137},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.19307},
	doi = {10.1111/nph.19307},
	abstract = {Stem bending in trees induces flexure wood but its properties and development are poorly understood. Here, we investigated the effects of low-intensity multidirectional stem flexing on growth and wood properties of hybrid aspen, and on its transcriptomic and hormonal responses. Glasshouse-grown trees were either kept stationary or subjected to several daily shakes for 5 wk, after which the transcriptomes and hormones were analyzed in the cambial region and developing wood tissues, and the wood properties were analyzed by physical, chemical and microscopy techniques. Shaking increased primary and secondary growth and altered wood differentiation by stimulating gelatinous-fiber formation, reducing secondary wall thickness, changing matrix polysaccharides and increasing cellulose, G- and H-lignin contents, cell wall porosity and saccharification yields. Wood-forming tissues exhibited elevated jasmonate, polyamine, ethylene and brassinosteroids and reduced abscisic acid and gibberellin signaling. Transcriptional responses resembled those during tension wood formation but not opposite wood formation and revealed several thigmomorphogenesis-related genes as well as novel gene networks including FLA and XTH genes encoding plasma membrane-bound proteins. Low-intensity stem flexing stimulates growth and induces wood having improved biorefinery properties through molecular and hormonal pathways similar to thigmomorphogenesis in herbaceous plants and largely overlapping with the tension wood program of hardwoods.},
	language = {en},
	urldate = {2023-10-20},
	journal = {New Phytologist},
	author = {Urbancsok, János and Donev, Evgeniy N. and Sivan, Pramod and van Zalen, Elena and Barbut, Félix R. and Derba-Maceluch, Marta and Šimura, Jan and Yassin, Zakiya and Gandla, Madhavi L. and Karady, Michal and Ljung, Karin and Winestrand, Sandra and Jönsson, Leif J. and Scheepers, Gerhard and Delhomme, Nicolas and Street, Nathaniel R. and Mellerowicz, Ewa J.},
	month = oct,
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/nph.19307},
	keywords = {Populus tremula × tremuloides, flexure wood, jasmonic acid signaling, mechanostimulation, polyamines, saccharification, thigmomorphogenesis, wood development},
}

Stem bending in trees induces flexure wood but its properties and development are poorly understood. Here, we investigated the effects of low-intensity multidirectional stem flexing on growth and wood properties of hybrid aspen, and on its transcriptomic and hormonal responses. Glasshouse-grown trees were either kept stationary or subjected to several daily shakes for 5 wk, after which the transcriptomes and hormones were analyzed in the cambial region and developing wood tissues, and the wood properties were analyzed by physical, chemical and microscopy techniques. Shaking increased primary and secondary growth and altered wood differentiation by stimulating gelatinous-fiber formation, reducing secondary wall thickness, changing matrix polysaccharides and increasing cellulose, G- and H-lignin contents, cell wall porosity and saccharification yields. Wood-forming tissues exhibited elevated jasmonate, polyamine, ethylene and brassinosteroids and reduced abscisic acid and gibberellin signaling. Transcriptional responses resembled those during tension wood formation but not opposite wood formation and revealed several thigmomorphogenesis-related genes as well as novel gene networks including FLA and XTH genes encoding plasma membrane-bound proteins. Low-intensity stem flexing stimulates growth and induces wood having improved biorefinery properties through molecular and hormonal pathways similar to thigmomorphogenesis in herbaceous plants and largely overlapping with the tension wood program of hardwoods.

@article{derba-maceluch_impact_2023,
	title = {Impact of xylan on field productivity and wood saccharification properties in aspen},
	volume = {14},
	issn = {1664-462X},
	url = {https://www.frontiersin.org/articles/10.3389/fpls.2023.1218302},
	doi = {10.3389/fpls.2023.1218302},
	abstract = {Xylan that comprises roughly 25\% of hardwood biomass is undesirable in biorefinery applications involving saccharification and fermentation. Efforts to reduce xylan levels have therefore been made in many species, usually resulting in improved saccharification. However, such modified plants have not yet been tested under field conditions. Here we evaluate the field performance of transgenic hybrid aspen lines with reduced xylan levels and assess their usefulness as short-rotation feedstocks for biorefineries. Three types of transgenic lines were tested in four-year field tests with RNAi constructs targeting either Populus GT43 clades B and C (GT43BC) corresponding to Arabidopsis clades IRX9 and IRX14, respectively, involved in xylan backbone biosynthesis, GATL1.1 corresponding to AtGALT1 involved in xylan reducing end sequence biosynthesis, or ASPR1 encoding an atypical aspartate protease. Their productivity, wood quality traits, and saccharification efficiency were analyzed. The only lines differing significantly from the wild type with respect to growth and biotic stress resistance were the ASPR1 lines, whose stems were roughly 10\% shorter and narrower and leaves showed increased arthropod damage. GT43BC lines exhibited no growth advantage in the field despite their superior growth in greenhouse experiments. Wood from the ASPR1 and GT43BC lines had slightly reduced density due to thinner cell walls and, in the case of ASPR1, larger cell diameters. The xylan was less extractable by alkali but more hydrolysable by acid, had increased glucuronosylation, and its content was reduced in all three types of transgenic lines. The hemicellulose size distribution in the GALT1.1 and ASPR1 lines was skewed towards higher molecular mass compared to the wild type. These results provide experimental evidence that GATL1.1 functions in xylan biosynthesis and suggest that ASPR1 may regulate this process. In saccharification without pretreatment, lines of all three constructs provided 8-11\% higher average glucose yields than wild-type plants. In saccharification with acid pretreatment, the GT43BC construct provided a 10\% yield increase on average. The best transgenic lines of each construct are thus predicted to modestly outperform the wild type in terms of glucose yields per hectare. The field evaluation of transgenic xylan-reduced aspen represents an important step towards more productive feedstocks for biorefineries.},
	urldate = {2023-07-18},
	journal = {Frontiers in Plant Science},
	author = {Derba-Maceluch, Marta and Sivan, Pramod and Donev, Evgeniy N. and Gandla, Madhavi Latha and Yassin, Zakiya and Vaasan, Rakhesh and Heinonen, Emilia and Andersson, Sanna and Amini, Fariba and Scheepers, Gerhard and Johansson, Ulf and Vilaplana, Francisco J. and Albrectsen, Benedicte R. and Hertzberg, Magnus and Jönsson, Leif J. and Mellerowicz, Ewa J.},
	year = {2023},
}

Xylan that comprises roughly 25% of hardwood biomass is undesirable in biorefinery applications involving saccharification and fermentation. Efforts to reduce xylan levels have therefore been made in many species, usually resulting in improved saccharification. However, such modified plants have not yet been tested under field conditions. Here we evaluate the field performance of transgenic hybrid aspen lines with reduced xylan levels and assess their usefulness as short-rotation feedstocks for biorefineries. Three types of transgenic lines were tested in four-year field tests with RNAi constructs targeting either Populus GT43 clades B and C (GT43BC) corresponding to Arabidopsis clades IRX9 and IRX14, respectively, involved in xylan backbone biosynthesis, GATL1.1 corresponding to AtGALT1 involved in xylan reducing end sequence biosynthesis, or ASPR1 encoding an atypical aspartate protease. Their productivity, wood quality traits, and saccharification efficiency were analyzed. The only lines differing significantly from the wild type with respect to growth and biotic stress resistance were the ASPR1 lines, whose stems were roughly 10% shorter and narrower and leaves showed increased arthropod damage. GT43BC lines exhibited no growth advantage in the field despite their superior growth in greenhouse experiments. Wood from the ASPR1 and GT43BC lines had slightly reduced density due to thinner cell walls and, in the case of ASPR1, larger cell diameters. The xylan was less extractable by alkali but more hydrolysable by acid, had increased glucuronosylation, and its content was reduced in all three types of transgenic lines. The hemicellulose size distribution in the GALT1.1 and ASPR1 lines was skewed towards higher molecular mass compared to the wild type. These results provide experimental evidence that GATL1.1 functions in xylan biosynthesis and suggest that ASPR1 may regulate this process. In saccharification without pretreatment, lines of all three constructs provided 8-11% higher average glucose yields than wild-type plants. In saccharification with acid pretreatment, the GT43BC construct provided a 10% yield increase on average. The best transgenic lines of each construct are thus predicted to modestly outperform the wild type in terms of glucose yields per hectare. The field evaluation of transgenic xylan-reduced aspen represents an important step towards more productive feedstocks for biorefineries.

@article{sivan_sequential_2023,
	title = {Sequential extraction of hemicelluloses by subcritical water improves saccharification of hybrid aspen wood grown in greenhouse and field conditions},
	volume = {25},
	issn = {1463-9270},
	url = {https://pubs.rsc.org/en/content/articlelanding/2023/gc/d3gc01020a},
	doi = {10.1039/D3GC01020A},
	abstract = {Fast growing hardwoods are one of the major renewable resources available to produce bio-based materials, platform chemicals and biofuels. However, the industrial processing of lignocellulosic biomass is hindered by the complex molecular structure of the cell wall components and their supramolecular organization. This highlights the necessity of improving green processing strategies to enhance biomass conversion to valuable products from industrial wood production species. In the present study, we implemented a hydrothermal step by sequential subcritical water (SW) in aspen wood prior to saccharification and validated the process for trees grown in greenhouse and field conditions. Subcritical water enables extraction of non-cellulosic cell wall polysaccharides in native polymeric form. A major part of the pectic fraction was easily extracted within the first 10 min, while acetylated xylan was enriched in the subsequent extracts after 20- and 30-min rounds. Prolonged extraction (above 60 min) resulted in partial deacetylation and a reduction of the molar mass of xylan. The analysis of the residues enriched with cellulose and lignin showed several micromorphological changes caused by subcritical water treatment, such as an increased porosity, a loosening of the fibre matrix and a decrease in the macrofibrillar dimensions. These morphological and molecular changes in the organization of cell wall polymers after SW treatment significantly enhanced saccharification yields compared to those of non-treated aspen wood chips from both field and greenhouse conditions. Our study demonstrates that SW can be implemented as pretreatment prior to saccharification reducing the requirements for chemical acid pretreatments. This process enables the extraction of native non-cellulosic cell wall polymers for potential material applications and promotes the subsequent biochemical conversion of the residual biomass into fermentable sugars and platform chemicals in future biorefineries.},
	language = {en},
	number = {14},
	urldate = {2023-07-18},
	journal = {Green Chemistry},
	author = {Sivan, Pramod and Heinonen, Emilia and Gandla, Madhavi Latha and Jiménez-Quero, Amparo and Özeren, Hüsamettin Deniz and Jönsson, Leif J. and Mellerowicz, Ewa J. and Vilaplana, Francisco},
	month = jul,
	year = {2023},
	note = {Publisher: The Royal Society of Chemistry},
	pages = {5634--5646},
}

Fast growing hardwoods are one of the major renewable resources available to produce bio-based materials, platform chemicals and biofuels. However, the industrial processing of lignocellulosic biomass is hindered by the complex molecular structure of the cell wall components and their supramolecular organization. This highlights the necessity of improving green processing strategies to enhance biomass conversion to valuable products from industrial wood production species. In the present study, we implemented a hydrothermal step by sequential subcritical water (SW) in aspen wood prior to saccharification and validated the process for trees grown in greenhouse and field conditions. Subcritical water enables extraction of non-cellulosic cell wall polysaccharides in native polymeric form. A major part of the pectic fraction was easily extracted within the first 10 min, while acetylated xylan was enriched in the subsequent extracts after 20- and 30-min rounds. Prolonged extraction (above 60 min) resulted in partial deacetylation and a reduction of the molar mass of xylan. The analysis of the residues enriched with cellulose and lignin showed several micromorphological changes caused by subcritical water treatment, such as an increased porosity, a loosening of the fibre matrix and a decrease in the macrofibrillar dimensions. These morphological and molecular changes in the organization of cell wall polymers after SW treatment significantly enhanced saccharification yields compared to those of non-treated aspen wood chips from both field and greenhouse conditions. Our study demonstrates that SW can be implemented as pretreatment prior to saccharification reducing the requirements for chemical acid pretreatments. This process enables the extraction of native non-cellulosic cell wall polymers for potential material applications and promotes the subsequent biochemical conversion of the residual biomass into fermentable sugars and platform chemicals in future biorefineries.

@article{derba-maceluch_xylan_2023,
	title = {Xylan glucuronic acid side chains fix suberin-like aliphatic compounds to wood cell walls},
	volume = {238},
	issn = {1469-8137},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.18712},
	doi = {10.1111/nph.18712},
	abstract = {Wood is the most important repository of assimilated carbon in the biosphere, in the form of large polymers (cellulose, hemicelluloses including glucuronoxylan, and lignin) that interactively form a composite, together with soluble extractives including phenolic and aliphatic compounds. Molecular interactions among these compounds are not fully understood. We have targeted the expression of a fungal α-glucuronidase to the wood cell wall of aspen (Populus tremula L. × tremuloides Michx.) and Arabidopsis (Arabidopsis thaliana (L.) Heynh), to decrease contents of the 4-O-methyl glucuronopyranose acid (mGlcA) substituent of xylan, to elucidate mGlcA's functions. The enzyme affected the content of aliphatic insoluble cell wall components having composition similar to suberin, which required mGlcA for binding to cell walls. Such suberin-like compounds have been previously identified in decayed wood, but here, we show their presence in healthy wood of both hardwood and softwood species. By contrast, γ-ester bonds between mGlcA and lignin were insensitive to cell wall-localized α-glucuronidase, supporting the intracellular formation of these bonds. These findings challenge the current view of the wood cell wall composition and reveal a novel function of mGlcA substituent of xylan in fastening of suberin-like compounds to cell wall. They also suggest an intracellular initiation of lignin–carbohydrate complex assembly.},
	language = {en},
	number = {1},
	urldate = {2023-03-10},
	journal = {New Phytologist},
	author = {Derba-Maceluch, Marta and Mitra, Madhusree and Hedenström, Mattias and Liu, Xiaokun and Gandla, Madhavi L. and Barbut, Félix R. and Abreu, Ilka N. and Donev, Evgeniy N. and Urbancsok, János and Moritz, Thomas and Jönsson, Leif J. and Tsang, Adrian and Powlowski, Justin and Master, Emma R. and Mellerowicz, Ewa J.},
	month = jan,
	year = {2023},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/nph.18712},
	keywords = {Populus, lignin-carbohydrate complexes (LCCs), lignin–carbohydrate complexes, saccharification, suberin, wood cell wall, xylan},
	pages = {297--312},
}

Wood is the most important repository of assimilated carbon in the biosphere, in the form of large polymers (cellulose, hemicelluloses including glucuronoxylan, and lignin) that interactively form a composite, together with soluble extractives including phenolic and aliphatic compounds. Molecular interactions among these compounds are not fully understood. We have targeted the expression of a fungal α-glucuronidase to the wood cell wall of aspen (Populus tremula L. × tremuloides Michx.) and Arabidopsis (Arabidopsis thaliana (L.) Heynh), to decrease contents of the 4-O-methyl glucuronopyranose acid (mGlcA) substituent of xylan, to elucidate mGlcA's functions. The enzyme affected the content of aliphatic insoluble cell wall components having composition similar to suberin, which required mGlcA for binding to cell walls. Such suberin-like compounds have been previously identified in decayed wood, but here, we show their presence in healthy wood of both hardwood and softwood species. By contrast, γ-ester bonds between mGlcA and lignin were insensitive to cell wall-localized α-glucuronidase, supporting the intracellular formation of these bonds. These findings challenge the current view of the wood cell wall composition and reveal a novel function of mGlcA substituent of xylan in fastening of suberin-like compounds to cell wall. They also suggest an intracellular initiation of lignin–carbohydrate complex assembly.

@article{majda_elongation_2021,
	title = {Elongation of wood fibers combines features of diffuse and tip growth},
	issn = {0028-646X, 1469-8137},
	url = {https://onlinelibrary.wiley.com/doi/10.1111/nph.17468},
	doi = {10/gj3qbx},
	language = {en},
	urldate = {2021-06-03},
	journal = {New Phytologist},
	author = {Majda, Mateusz and Kozlova, Liudmila and Banasiak, Alicja and Derba‐Maceluch, Marta and Iashchishyn, Igor A. and Morozova‐Roche, Ludmilla A. and Smith, Richard S. and Gorshkova, Tatyana and Mellerowicz, Ewa J.},
	month = may,
	year = {2021},
	pages = {nph.17468},
}

@article{pramod_saccharification_2021,
	title = {Saccharification {Potential} of {Transgenic} {Greenhouse}- and {Field}-{Grown} {Aspen} {Engineered} for {Reduced} {Xylan} {Acetylation}},
	volume = {12},
	issn = {1664-462X},
	url = {https://www.frontiersin.org/article/10.3389/fpls.2021.704960},
	doi = {10.3389/fpls.2021.704960},
	abstract = {High acetylation of xylan in hardwoods decreases their value as biorefinery feedstocks. To counter this problem, we have constitutively suppressed RWA genes encoding acetyl-CoA transporters using the 35S promoter, or constitutively and wood-specifically (using the WP promoter) expressed fungal acetyl xylan esterases of families CE1 (AnAXE1) and CE5 (HjAXE), to reduce acetylation in hybrid aspen. All these transformations improved the saccharification of wood from greenhouse-grown trees. Here, we describe the chemical properties and saccharification potential of the resulting lines grown in a five-year field trial, and one type of them (WP:AnAXE1) in greenhouse conditions. Chemically, the lignocellulose of the field- and greenhouse-field-grown plants slightly differed, but the reductions in acetylation and saccharification improvement of engineered trees were largely maintained in the field. The main novel phenotypic observation in the field was higher lignification in lines with the WP promoter than those with the 35S promoter. Following growth in the field, saccharification glucose yields were higher from most transformed lines than from wild-type (WT) plants with no pretreatment, but there was no improvement in saccharification with acid pretreatment. Thus, acid pretreatment removes most recalcitrance caused by acetylation. We found a complex relationship between acetylation and glucose yields in saccharification without pretreatment, suggesting that other variables, for example, the acetylation pattern, affect recalcitrance. Bigger gains in glucose yields were observed in lines with the 35S promoter than in those with the WP promoter, possibly due to their lower lignin content. However, better lignocellulose saccharification of these lines was offset by a growth penalty and their glucose yield per tree was lower. In a comparison of the best lines with each construct, WP:AnAXE1 provided the highest glucose yield per tree from saccharification, with and without pretreatment, WP:HjAXE yields were similar to those of WT plants, and yields of lines with other constructs were lower. These results show that lignocellulose properties of field-grown trees can be improved by reducing cell wall acetylation using various approaches, but some affect productivity in the field. Thus, better understanding of molecular and physiological consequences of deacetylation is needed to obtain quantitatively better results.},
	urldate = {2021-09-30},
	journal = {Frontiers in Plant Science},
	author = {Pramod, Sivan and Gandla, Madhavi Latha and Derba-Maceluch, Marta and Jönsson, Leif J. and Mellerowicz, Ewa J. and Winestrand, Sandra},
	year = {2021},
	pages = {1722},
}

High acetylation of xylan in hardwoods decreases their value as biorefinery feedstocks. To counter this problem, we have constitutively suppressed RWA genes encoding acetyl-CoA transporters using the 35S promoter, or constitutively and wood-specifically (using the WP promoter) expressed fungal acetyl xylan esterases of families CE1 (AnAXE1) and CE5 (HjAXE), to reduce acetylation in hybrid aspen. All these transformations improved the saccharification of wood from greenhouse-grown trees. Here, we describe the chemical properties and saccharification potential of the resulting lines grown in a five-year field trial, and one type of them (WP:AnAXE1) in greenhouse conditions. Chemically, the lignocellulose of the field- and greenhouse-field-grown plants slightly differed, but the reductions in acetylation and saccharification improvement of engineered trees were largely maintained in the field. The main novel phenotypic observation in the field was higher lignification in lines with the WP promoter than those with the 35S promoter. Following growth in the field, saccharification glucose yields were higher from most transformed lines than from wild-type (WT) plants with no pretreatment, but there was no improvement in saccharification with acid pretreatment. Thus, acid pretreatment removes most recalcitrance caused by acetylation. We found a complex relationship between acetylation and glucose yields in saccharification without pretreatment, suggesting that other variables, for example, the acetylation pattern, affect recalcitrance. Bigger gains in glucose yields were observed in lines with the 35S promoter than in those with the WP promoter, possibly due to their lower lignin content. However, better lignocellulose saccharification of these lines was offset by a growth penalty and their glucose yield per tree was lower. In a comparison of the best lines with each construct, WP:AnAXE1 provided the highest glucose yield per tree from saccharification, with and without pretreatment, WP:HjAXE yields were similar to those of WT plants, and yields of lines with other constructs were lower. These results show that lignocellulose properties of field-grown trees can be improved by reducing cell wall acetylation using various approaches, but some affect productivity in the field. Thus, better understanding of molecular and physiological consequences of deacetylation is needed to obtain quantitatively better results.

@article{dominguez_sucrose_2021,
	title = {Sucrose synthase determines carbon allocation in developing wood and alters carbon flow at the whole tree level in aspen},
	volume = {229},
	issn = {0028-646X, 1469-8137},
	url = {https://onlinelibrary.wiley.com/doi/10.1111/nph.16721},
	doi = {10.1111/nph.16721},
	language = {en},
	number = {1},
	urldate = {2021-06-07},
	journal = {New Phytologist},
	author = {Dominguez, Pia Guadalupe and Donev, Evgeniy and Derba‐Maceluch, Marta and Bünder, Anne and Hedenström, Mattias and Tomášková, Ivana and Mellerowicz, Ewa J. and Niittylä, Totte},
	month = jan,
	year = {2021},
	pages = {186--198},
}

@article{kushwah_arabidopsis_2020,
	title = {Arabidopsis \textit{{XTH4}} and \textit{{XTH9}} {Contribute} to {Wood} {Cell} {Expansion} and {Secondary} {Wall} {Formation}},
	volume = {182},
	issn = {0032-0889, 1532-2548},
	url = {https://academic.oup.com/plphys/article/182/4/1946-1965/6116228},
	doi = {10.1104/pp.19.01529},
	language = {en},
	number = {4},
	urldate = {2021-06-07},
	journal = {Plant Physiology},
	author = {Kushwah, Sunita and Banasiak, Alicja and Nishikubo, Nobuyuki and Derba-Maceluch, Marta and Majda, Mateusz and Endo, Satoshi and Kumar, Vikash and Gomez, Leonardo and Gorzsas, Andras and McQueen-Mason, Simon and Braam, Janet and Sundberg, Björn and Mellerowicz, Ewa J.},
	month = apr,
	year = {2020},
	pages = {1946--1965},
}

@article{derba-maceluch_cell_2020,
	title = {Cell {Wall} {Acetylation} in {Hybrid} {Aspen} {Affects} {Field} {Performance}, {Foliar} {Phenolic} {Composition} and {Resistance} to {Biological} {Stress} {Factors} in a {Construct}-{Dependent} {Fashion}},
	volume = {11},
	issn = {1664-462X},
	url = {https://www.frontiersin.org/article/10.3389/fpls.2020.00651/full},
	doi = {10.3389/fpls.2020.00651},
	urldate = {2021-06-07},
	journal = {Frontiers in Plant Science},
	author = {Derba-Maceluch, Marta and Amini, Fariba and Donev, Evgeniy N. and Pawar, Prashant Mohan-Anupama and Michaud, Lisa and Johansson, Ulf and Albrectsen, Benedicte R. and Mellerowicz, Ewa J.},
	month = may,
	year = {2020},
	pages = {651},
}

@incollection{popper_expression_2020,
	address = {New York, NY},
	title = {Expression of {Cell} {Wall}–{Modifying} {Enzymes} in {Aspen} for {Improved} {Lignocellulose} {Processing}},
	volume = {2149},
	isbn = {978-1-07-160619-3 978-1-07-160621-6},
	url = {http://link.springer.com/10.1007/978-1-0716-0621-6_9},
	language = {en},
	urldate = {2021-06-07},
	booktitle = {The {Plant} {Cell} {Wall}},
	publisher = {Springer New York},
	author = {Derba-Maceluch, Marta and Mellerowicz, Ewa J.},
	editor = {Popper, Zoë A.},
	year = {2020},
	doi = {10.1007/978-1-0716-0621-6_9},
	note = {Series Title: Methods in Molecular Biology},
	pages = {145--164},
}

@article{baison_genetic_2020,
	title = {Genetic control of tracheid properties in {Norway} spruce wood},
	volume = {10},
	issn = {2045-2322},
	url = {http://www.nature.com/articles/s41598-020-72586-3},
	doi = {10.1038/s41598-020-72586-3},
	abstract = {Abstract
            
              Through the use of genome-wide association studies (GWAS) mapping it is possible to establish the genetic basis of phenotypic trait variation. Our GWAS study presents the first such effort in Norway spruce (
              Picea abies
              (L). Karst.) for the traits related to wood tracheid characteristics. The study employed an exome capture genotyping approach that generated 178 101 Single Nucleotide Polymorphisms (SNPs) from 40 018 probes within a population of 517 Norway spruce mother trees. We applied a least absolute shrinkage and selection operator (LASSO) based association mapping method using a functional multi-locus mapping approach, with a stability selection probability method as the hypothesis testing approach to determine significant Quantitative Trait Loci (QTLs). The analysis has provided 30 significant associations, the majority of which show specific expression in wood-forming tissues or high ubiquitous expression, potentially controlling tracheids dimensions, their cell wall thickness and microfibril angle. Among the most promising candidates based on our results and prior information for other species are:
              Picea abies BIG GRAIN 2
              (
              PabBG2)
              with a predicted function in auxin transport and sensitivity, and
              MA\_373300g0010
              encoding a protein similar to wall-associated receptor kinases, which were both associated with cell wall thickness. The results demonstrate feasibility of GWAS to identify novel candidate genes controlling industrially-relevant tracheid traits in Norway spruce.},
	language = {en},
	number = {1},
	urldate = {2021-06-07},
	journal = {Scientific Reports},
	author = {Baison, J. and Zhou, Linghua and Forsberg, Nils and Mörling, Tommy and Grahn, Thomas and Olsson, Lars and Karlsson, Bo and Wu, Harry X. and Mellerowicz, Ewa J. and Lundqvist, Sven-Olof and García-Gil, María Rosario},
	month = dec,
	year = {2020},
	pages = {18089},
}

Abstract Through the use of genome-wide association studies (GWAS) mapping it is possible to establish the genetic basis of phenotypic trait variation. Our GWAS study presents the first such effort in Norway spruce ( Picea abies (L). Karst.) for the traits related to wood tracheid characteristics. The study employed an exome capture genotyping approach that generated 178 101 Single Nucleotide Polymorphisms (SNPs) from 40 018 probes within a population of 517 Norway spruce mother trees. We applied a least absolute shrinkage and selection operator (LASSO) based association mapping method using a functional multi-locus mapping approach, with a stability selection probability method as the hypothesis testing approach to determine significant Quantitative Trait Loci (QTLs). The analysis has provided 30 significant associations, the majority of which show specific expression in wood-forming tissues or high ubiquitous expression, potentially controlling tracheids dimensions, their cell wall thickness and microfibril angle. Among the most promising candidates based on our results and prior information for other species are: Picea abies BIG GRAIN 2 ( PabBG2) with a predicted function in auxin transport and sensitivity, and MA_373300g0010 encoding a protein similar to wall-associated receptor kinases, which were both associated with cell wall thickness. The results demonstrate feasibility of GWAS to identify novel candidate genes controlling industrially-relevant tracheid traits in Norway spruce.

@article{kumar_genome-wide_2020,
	title = {Genome-{Wide} {Identification} of {Populus} {Malectin}/{Malectin}-{Like} {Domain}-{Containing} {Proteins} and {Expression} {Analyses} {Reveal} {Novel} {Candidates} for {Signaling} and {Regulation} of {Wood} {Development}},
	volume = {11},
	issn = {1664-462X},
	url = {https://www.frontiersin.org/articles/10.3389/fpls.2020.588846/full},
	doi = {10/gjcxjw},
	abstract = {Malectin domain (MD) is a ligand-binding protein motif of pro- and eukaryotes. It is particularly abundant in Viridiplantae, where it occurs as either a single (MD, PF11721) or tandemly duplicated domain (PF12819) called malectin-like domain (MLD). In herbaceous plants, MD- or MLD-containing proteins (MD proteins) are known to regulate development, reproduction, and resistance to various stresses. However, their functions in woody plants have not yet been studied. To unravel their potential role in wood development, we carried out genome-wide identification of MD proteins in the model tree species black cottonwood (
              Populus trichocarpa
              ), and analyzed their expression and co-expression networks.
              P. trichocarpa
              had 146
              MD
              genes assigned to 14 different clades, two of which were specific to the genus
              Populus
              . 87\% of these genes were located on chromosomes, the rest being associated with scaffolds. Based on their protein domain organization, and in agreement with the exon-intron structures, the
              MD
              genes identified here could be classified into five superclades having the following domains: leucine-rich repeat (LRR)-MD-protein kinase (PK), MLD-LRR-PK, MLD-PK (
              Cr
              RLK1L), MLD-LRR, and MD-Kinesin. Whereas the majority of
              MD
              genes were highly expressed in leaves, particularly under stress conditions, eighteen showed a peak of expression during secondary wall formation in the xylem and their co-expression networks suggested signaling functions in cell wall integrity, pathogen-associated molecular patterns, calcium, ROS, and hormone pathways. Thus,
              P. trichocarpa MD
              genes having different domain organizations comprise many genes with putative foliar defense functions, some of which could be specific to
              Populus
              and related species, as well as genes with potential involvement in signaling pathways in other tissues including developing wood.},
	urldate = {2021-06-03},
	journal = {Frontiers in Plant Science},
	author = {Kumar, Vikash and Donev, Evgeniy N. and Barbut, Félix R. and Kushwah, Sunita and Mannapperuma, Chanaka and Urbancsok, János and Mellerowicz, Ewa J.},
	month = dec,
	year = {2020},
	pages = {588846},
}

Malectin domain (MD) is a ligand-binding protein motif of pro- and eukaryotes. It is particularly abundant in Viridiplantae, where it occurs as either a single (MD, PF11721) or tandemly duplicated domain (PF12819) called malectin-like domain (MLD). In herbaceous plants, MD- or MLD-containing proteins (MD proteins) are known to regulate development, reproduction, and resistance to various stresses. However, their functions in woody plants have not yet been studied. To unravel their potential role in wood development, we carried out genome-wide identification of MD proteins in the model tree species black cottonwood ( Populus trichocarpa ), and analyzed their expression and co-expression networks. P. trichocarpa had 146 MD genes assigned to 14 different clades, two of which were specific to the genus Populus . 87% of these genes were located on chromosomes, the rest being associated with scaffolds. Based on their protein domain organization, and in agreement with the exon-intron structures, the MD genes identified here could be classified into five superclades having the following domains: leucine-rich repeat (LRR)-MD-protein kinase (PK), MLD-LRR-PK, MLD-PK ( Cr RLK1L), MLD-LRR, and MD-Kinesin. Whereas the majority of MD genes were highly expressed in leaves, particularly under stress conditions, eighteen showed a peak of expression during secondary wall formation in the xylem and their co-expression networks suggested signaling functions in cell wall integrity, pathogen-associated molecular patterns, calcium, ROS, and hormone pathways. Thus, P. trichocarpa MD genes having different domain organizations comprise many genes with putative foliar defense functions, some of which could be specific to Populus and related species, as well as genes with potential involvement in signaling pathways in other tissues including developing wood.

@article{wang_hybrid_2020,
	title = {Hybrid {Aspen} {Expressing} a {Carbohydrate} {Esterase} {Family} 5 {Acetyl} {Xylan} {Esterase} {Under} {Control} of a {Wood}-{Specific} {Promoter} {Shows} {Improved} {Saccharification}},
	volume = {11},
	issn = {1664-462X},
	url = {https://www.frontiersin.org/article/10.3389/fpls.2020.00380/full},
	doi = {10.3389/fpls.2020.00380},
	urldate = {2021-06-07},
	journal = {Frontiers in Plant Science},
	author = {Wang, Zhao and Pawar, Prashant Mohan-Anupama and Derba-Maceluch, Marta and Hedenström, Mattias and Chong, Sun-Li and Tenkanen, Maija and Jönsson, Leif J. and Mellerowicz, Ewa J.},
	month = apr,
	year = {2020},
	pages = {380},
}

@article{kumar_poplar_2019,
	title = {Poplar carbohydrate‐active enzymes: whole‐genome annotation and functional analyses based on {RNA} expression data},
	volume = {99},
	issn = {0960-7412, 1365-313X},
	shorttitle = {Poplar carbohydrate‐active enzymes},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/tpj.14417},
	doi = {10.1111/tpj.14417},
	language = {en},
	number = {4},
	urldate = {2021-06-07},
	journal = {The Plant Journal},
	author = {Kumar, Vikash and Hainaut, Matthieu and Delhomme, Nicolas and Mannapperuma, Chanaka and Immerzeel, Peter and Street, Nathaniel R. and Henrissat, Bernard and Mellerowicz, Ewa J.},
	month = aug,
	year = {2019},
	pages = {589--609},
}

@article{ratke_downregulating_2018,
	title = {Downregulating aspen xylan biosynthetic {GT43} genes in developing wood stimulates growth via reprograming of the transcriptome},
	volume = {219},
	issn = {0028646X},
	url = {http://doi.wiley.com/10.1111/nph.15160},
	doi = {10/gdmzzr},
	language = {en},
	number = {1},
	urldate = {2021-06-07},
	journal = {New Phytologist},
	author = {Ratke, Christine and Terebieniec, Barbara K. and Winestrand, Sandra and Derba-Maceluch, Marta and Grahn, Thomas and Schiffthaler, Bastian and Ulvcrona, Thomas and Özparpucu, Merve and Rüggeberg, Markus and Lundqvist, Sven-Olof and Street, Nathaniel R. and Jönsson, Leif J. and Mellerowicz, Ewa J.},
	month = jul,
	year = {2018},
	pages = {230--245},
}

@article{donev_engineering_2018,
	title = {Engineering {Non}-cellulosic {Polysaccharides} of {Wood} for the {Biorefinery}},
	volume = {9},
	issn = {1664-462X},
	url = {https://www.frontiersin.org/article/10.3389/fpls.2018.01537/full},
	doi = {10/gjcq6g},
	urldate = {2021-06-07},
	journal = {Frontiers in Plant Science},
	author = {Donev, Evgeniy and Gandla, Madhavi Latha and Jönsson, Leif J. and Mellerowicz, Ewa J.},
	month = oct,
	year = {2018},
	pages = {1537},
}

@article{felten_ethylene_2018,
	title = {Ethylene signaling induces gelatinous layers with typical features of tension wood in hybrid aspen},
	volume = {218},
	issn = {0028646X},
	url = {http://doi.wiley.com/10.1111/nph.15078},
	doi = {10.1111/nph.15078},
	language = {en},
	number = {3},
	urldate = {2021-06-07},
	journal = {New Phytologist},
	author = {Felten, Judith and Vahala, Jorma and Love, Jonathan and Gorzsás, András and Rüggeberg, Markus and Delhomme, Nicolas and Leśniewska, Joanna and Kangasjärvi, Jaakko and Hvidsten, Torgeir R. and Mellerowicz, Ewa J. and Sundberg, Björn},
	month = may,
	year = {2018},
	pages = {999--1014},
}

@article{hayatgheibi_genetic_2018,
	title = {Genetic control of transition from juvenile to mature wood with respect to microfibril angle in {Norway} spruce ( \textit{{Picea} abies} ) and lodgepole pine ( \textit{{Pinus} contorta} )},
	volume = {48},
	issn = {0045-5067, 1208-6037},
	url = {http://www.nrcresearchpress.com/doi/10.1139/cjfr-2018-0140},
	doi = {10.1139/cjfr-2018-0140},
	abstract = {Genetic control of microfibril angle (MFA) transition from juvenile wood to mature wood was evaluated in Norway spruce (Picea abies (L.) Karst) and lodgepole pine (Pinus contorta Douglas ex Loudon). Increment cores were collected at breast height (1.3 m) from 5664 trees in two 21-year-old Norway spruce progeny trials in southern Sweden and from 823 trees in two lodgepole pine progeny trials, aged 34–35 years, in northern Sweden. Radial variations in MFA from pith to bark were measured for each core using SilviScan. To estimate MFA transition from juvenile wood to mature wood, a threshold level of MFA 20° was considered, and six different regression functions were fitted to the MFA profile of each tree after exclusion of outliers, following three steps. The narrow-sense heritability estimates (h
              2
              ) obtained for MFA transition were highest based on the slope function, ranging from 0.21 to 0.23 for Norway spruce and from 0.34 to 0.53 for lodgepole pine, while h
              2
              were mostly non-significant based on the logistic function, under all exclusion methods. Results of this study indicate that it is possible to select for an earlier MFA transition from juvenile wood to mature wood in Norway spruce and lodgepole pine selective breeding programs, as the genetic gains (ΔG) obtained in direct selection of this trait were very high in both species.},
	language = {en},
	number = {11},
	urldate = {2021-06-07},
	journal = {Canadian Journal of Forest Research},
	author = {Hayatgheibi, Haleh and Forsberg, Nils Erik Gustaf and Lundqvist, Sven-Olof and Mörling, Tommy and Mellerowicz, Ewa J. and Karlsson, Bo and Wu, Harry X. and García-Gil, M. Rosario},
	month = nov,
	year = {2018},
	pages = {1358--1365},
}

Genetic control of microfibril angle (MFA) transition from juvenile wood to mature wood was evaluated in Norway spruce (Picea abies (L.) Karst) and lodgepole pine (Pinus contorta Douglas ex Loudon). Increment cores were collected at breast height (1.3 m) from 5664 trees in two 21-year-old Norway spruce progeny trials in southern Sweden and from 823 trees in two lodgepole pine progeny trials, aged 34–35 years, in northern Sweden. Radial variations in MFA from pith to bark were measured for each core using SilviScan. To estimate MFA transition from juvenile wood to mature wood, a threshold level of MFA 20° was considered, and six different regression functions were fitted to the MFA profile of each tree after exclusion of outliers, following three steps. The narrow-sense heritability estimates (h 2 ) obtained for MFA transition were highest based on the slope function, ranging from 0.21 to 0.23 for Norway spruce and from 0.34 to 0.53 for lodgepole pine, while h 2 were mostly non-significant based on the logistic function, under all exclusion methods. Results of this study indicate that it is possible to select for an earlier MFA transition from juvenile wood to mature wood in Norway spruce and lodgepole pine selective breeding programs, as the genetic gains (ΔG) obtained in direct selection of this trait were very high in both species.

@article{allario_ptxtpme1_2018,
	title = {{PtxtPME1} and homogalacturonans influence xylem hydraulic properties in poplar},
	volume = {163},
	copyright = {© 2018 Scandinavian Plant Physiology Society},
	issn = {1399-3054},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/ppl.12702},
	doi = {10/gcxrch},
	abstract = {While the xylem hydraulic properties, such as vulnerability to cavitation (VC), are of paramount importance in drought resistance, their genetic determinants remain unexplored. There is evidence that pectins and their methylation pattern are involved, but the detail of their involvement and the corresponding genes need to be clarified. We analyzed the hydraulic properties of the 35S::PME1 transgenic aspen that ectopically under- or over-express a xylem-abundant pectin methyl esterase, PtxtPME1. We also produced and analyzed 4CL1::PGII transgenic poplars expressing a fungal polygalacturonase, AnPGII, under the control of the Ptxa4CL1 promoter that is active in the developing xylem after xylem cell expansion. Both the 35S::PME1 under- and over-expressing aspen lines developed xylem with lower-specific hydraulic conductivity and lower VC, while the 4CL1::PGII plants developed xylem with a higher VC. These xylem hydraulic changes were associated with modifications in xylem structure or in intervessel pit structure that can result in changes in mechanical behavior of the pit membrane. This study shows that homogalacturonans and their methylation pattern influence xylem hydraulic properties, through its effect on xylem cell expansion and on intervessel pit properties and it show a role for PtxtPME1 in the xylem hydraulic properties.},
	language = {en},
	number = {4},
	urldate = {2021-06-21},
	journal = {Physiologia Plantarum},
	author = {Allario, Thierry and Tixier, Aude and Awad, Hosam and Lemaire, Cedric and Brunel, Nicole and Badel, Eric and Barigah, Têtè S. and Julien, Jean-Louis and Peyret, Pierre and Mellerowicz, Ewa J. and Cochard, Herve and Herbette, Stephane},
	year = {2018},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/ppl.12702},
	pages = {502--515},
}

While the xylem hydraulic properties, such as vulnerability to cavitation (VC), are of paramount importance in drought resistance, their genetic determinants remain unexplored. There is evidence that pectins and their methylation pattern are involved, but the detail of their involvement and the corresponding genes need to be clarified. We analyzed the hydraulic properties of the 35S::PME1 transgenic aspen that ectopically under- or over-express a xylem-abundant pectin methyl esterase, PtxtPME1. We also produced and analyzed 4CL1::PGII transgenic poplars expressing a fungal polygalacturonase, AnPGII, under the control of the Ptxa4CL1 promoter that is active in the developing xylem after xylem cell expansion. Both the 35S::PME1 under- and over-expressing aspen lines developed xylem with lower-specific hydraulic conductivity and lower VC, while the 4CL1::PGII plants developed xylem with a higher VC. These xylem hydraulic changes were associated with modifications in xylem structure or in intervessel pit structure that can result in changes in mechanical behavior of the pit membrane. This study shows that homogalacturonans and their methylation pattern influence xylem hydraulic properties, through its effect on xylem cell expansion and on intervessel pit properties and it show a role for PtxtPME1 in the xylem hydraulic properties.

@article{pawar_qtl_2018,
	title = {{QTL} {Mapping} of {Wood} {FT}-{IR} {Chemotypes} {Shows} {Promise} for {Improving} {Biofuel} {Potential} in {Short} {Rotation} {Coppice} {Willow} ({Salix} spp.)},
	volume = {11},
	issn = {1939-1242},
	url = {https://doi.org/10.1007/s12155-018-9901-8},
	doi = {10.1007/s12155-018-9901-8},
	abstract = {An increasing interest to convert lignocellulosic biomass into biofuels has highlighted the potential of using willows for this purpose, due to its fast growth in short rotation coppice systems. Here, we use a mapping population of 463 individuals of a cross between Salix viminalis and S. viminalis × S. schwerinii to investigate the genetic background of different wood chemical traits, information of importance for breeding towards different uses of wood. Furthermore, using a subset of the mapping population, the correlation between biogas production and chemical traits was investigated. The phenotyping of wood was carried by Furrier-transformed-Infrared spectrometry (FT-IR) and water content analysis. Quantitative trait loci (QTLs) analysis was used to identify regions in the genome of importance for the phenotypic variation of these chemical traits. We found 27 QTLs for various traits. On linkage group (LG) VI-1, QTLs for signals assigned to G-lignin, lignin, and the S/G ratio were collocated and on LG XIV we found a cluster of QTLs representing signals assigned to lignin, cellulose, hemicellulose, and water. The QTLs explained from 3.4 to 6.9\% of the phenotypic variation indicating a quantitative genetic background where many genes influence the traits. For the biogas production, a positive and negative correlation was seen with the signals assigned to acetyl and lignin, respectively. This study represents a first step in the understanding of the genetic background of wood chemical traits for willows, information needed for complementary studies, mapping of important genes, and for breeding of varieties for biofuel production purposes.},
	language = {en},
	number = {2},
	urldate = {2021-06-07},
	journal = {BioEnergy Research},
	author = {Pawar, Prashant Mohan-Anupama and Schnürer, Anna and Mellerowicz, Ewa J. and Rönnberg-Wästljung, Ann Christin},
	month = jun,
	year = {2018},
	pages = {351--363},
}

An increasing interest to convert lignocellulosic biomass into biofuels has highlighted the potential of using willows for this purpose, due to its fast growth in short rotation coppice systems. Here, we use a mapping population of 463 individuals of a cross between Salix viminalis and S. viminalis × S. schwerinii to investigate the genetic background of different wood chemical traits, information of importance for breeding towards different uses of wood. Furthermore, using a subset of the mapping population, the correlation between biogas production and chemical traits was investigated. The phenotyping of wood was carried by Furrier-transformed-Infrared spectrometry (FT-IR) and water content analysis. Quantitative trait loci (QTLs) analysis was used to identify regions in the genome of importance for the phenotypic variation of these chemical traits. We found 27 QTLs for various traits. On linkage group (LG) VI-1, QTLs for signals assigned to G-lignin, lignin, and the S/G ratio were collocated and on LG XIV we found a cluster of QTLs representing signals assigned to lignin, cellulose, hemicellulose, and water. The QTLs explained from 3.4 to 6.9% of the phenotypic variation indicating a quantitative genetic background where many genes influence the traits. For the biogas production, a positive and negative correlation was seen with the signals assigned to acetyl and lignin, respectively. This study represents a first step in the understanding of the genetic background of wood chemical traits for willows, information needed for complementary studies, mapping of important genes, and for breeding of varieties for biofuel production purposes.

@article{armezzani_transcriptional_2018,
	title = {Transcriptional induction of cell wall remodelling genes is coupled to microtubule-driven growth isotropy at the shoot apex in {Arabidopsis}},
	issn = {1477-9129, 0950-1991},
	url = {https://journals.biologists.com/dev/article/doi/10.1242/dev.162255/264733/Transcriptional-induction-of-cell-wall-remodelling},
	doi = {10/gdhnxm},
	abstract = {The shoot apical meristem of higher plants continuously generates new tissues and organs through complex changes in growth rates and directions of its individual cells. Cell growth, driven by turgor pressure, largely depends on the cell walls, which allow cell expansion through synthesis and structural changes. A previous study revealed a major contribution of wall isotropy in organ emergence, through the disorganization of cortical microtubules. We show here that this disorganization is coupled with the transcriptional control of genes involved in wall remodelling. Some of these genes are induced when microtubules are disorganized and cells shift to isotropic growth. Mechanical modelling shows that this coupling has the potential to compensate for reduced cell expansion rates induced by the shift to isotropic growth. Reciprocally, cell wall loosening induced by different treatments or altered cell wall composition promotes a disruption of microtubule alignment. Our data thus indicate the existence of a regulatory module activated during organ outgrowth, linking microtubule arrangements to cell wall remodelling.},
	language = {en},
	urldate = {2021-06-07},
	journal = {Development},
	author = {Armezzani, Alessia and Abad, Ursula and Ali, Olivier and Robin, Amélie Andres and Vachez, Laetitia and Larrieu, Antoine and Mellerowicz, Ewa J. and Taconnat, Ludivine and Battu, Virginie and Stanislas, Thomas and Liu, Mengying and Vernoux, Teva and Traas, Jan and Sassi, Massimiliano},
	month = jan,
	year = {2018},
	pages = {dev.162255},
}

The shoot apical meristem of higher plants continuously generates new tissues and organs through complex changes in growth rates and directions of its individual cells. Cell growth, driven by turgor pressure, largely depends on the cell walls, which allow cell expansion through synthesis and structural changes. A previous study revealed a major contribution of wall isotropy in organ emergence, through the disorganization of cortical microtubules. We show here that this disorganization is coupled with the transcriptional control of genes involved in wall remodelling. Some of these genes are induced when microtubules are disorganized and cells shift to isotropic growth. Mechanical modelling shows that this coupling has the potential to compensate for reduced cell expansion rates induced by the shift to isotropic growth. Reciprocally, cell wall loosening induced by different treatments or altered cell wall composition promotes a disruption of microtubule alignment. Our data thus indicate the existence of a regulatory module activated during organ outgrowth, linking microtubule arrangements to cell wall remodelling.

@article{escamez_collection_2017,
	title = {A collection of genetically engineered {Populus} trees reveals wood biomass traits that predict glucose yield from enzymatic hydrolysis},
	volume = {7},
	issn = {2045-2322},
	url = {http://www.nature.com/articles/s41598-017-16013-0},
	doi = {10/gcmn8b},
	language = {en},
	number = {1},
	urldate = {2021-06-07},
	journal = {Scientific Reports},
	author = {Escamez, Sacha and Latha Gandla, Madhavi and Derba-Maceluch, Marta and Lundqvist, Sven-Olof and Mellerowicz, Ewa J. and Jönsson, Leif J. and Tuominen, Hannele},
	month = dec,
	year = {2017},
	pages = {15798},
}

@article{sundell_aspwood_2017,
	title = {{AspWood}: {High}-{Spatial}-{Resolution} {Transcriptome} {Profiles} {Reveal} {Uncharacterized} {Modularity} of {Wood} {Formation} in {Populus} tremula},
	volume = {29},
	issn = {1040-4651, 1532-298X},
	shorttitle = {{AspWood}},
	url = {https://academic.oup.com/plcell/article/29/7/1585-1604/6099151},
	doi = {10/gbshnb},
	language = {en},
	number = {7},
	urldate = {2021-06-07},
	journal = {The Plant Cell},
	author = {Sundell, David and Street, Nathaniel R. and Kumar, Manoj and Mellerowicz, Ewa J. and Kucukoglu, Melis and Johnsson, Christoffer and Kumar, Vikash and Mannapperuma, Chanaka and Delhomme, Nicolas and Nilsson, Ove and Tuominen, Hannele and Pesquet, Edouard and Fischer, Urs and Niittylä, Totte and Sundberg, Björn and Hvidsten, Torgeir R.},
	month = jul,
	year = {2017},
	pages = {1585--1604},
}

@article{lesniewska_defense_2017,
	title = {Defense {Responses} in {Aspen} with {Altered} {Pectin} {Methylesterase} {Activity} {Reveal} the {Hormonal} {Inducers} of {Tyloses}},
	volume = {173},
	issn = {0032-0889, 1532-2548},
	url = {https://academic.oup.com/plphys/article/173/2/1409-1419/6116100},
	doi = {10.1104/pp.16.01443},
	language = {en},
	number = {2},
	urldate = {2021-06-07},
	journal = {Plant Physiology},
	author = {Leśniewska, Joanna and Öhman, David and Krzesłowska, Magdalena and Kushwah, Sunita and Barciszewska-Pacak, Maria and Kleczkowski, Leszek A. and Sundberg, Björn and Moritz, Thomas and Mellerowicz, Ewa J.},
	month = feb,
	year = {2017},
	pages = {1409--1419},
}

@article{pawar_downregulation_2017,
	title = {Downregulation of {RWA} genes in hybrid aspen affects xylan acetylation and wood saccharification},
	volume = {214},
	copyright = {© 2017 The Authors. New Phytologist © 2017 New Phytologist Trust},
	issn = {1469-8137},
	url = {https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/nph.14489},
	doi = {https://doi.org/10.1111/nph.14489},
	abstract = {High acetylation of angiosperm wood hinders its conversion to sugars by glycoside hydrolases, subsequent ethanol fermentation and (hence) its use for biofuel production. We studied the REDUCED WALL ACETYLATION (RWA) gene family of the hardwood model Populus to evaluate its potential for improving saccharification. The family has two clades, AB and CD, containing two genes each. All four genes are expressed in developing wood but only RWA-A and -B are activated by master switches of the secondary cell wall PtNST1 and PtMYB21. Histochemical analysis of promoter::GUS lines in hybrid aspen (Populus tremula × tremuloides) showed activation of RWA-A and -B promoters in the secondary wall formation zone, while RWA-C and -D promoter activity was diffuse. Ectopic downregulation of either clade reduced wood xylan and xyloglucan acetylation. Suppressing both clades simultaneously using the wood-specific promoter reduced wood acetylation by 25\% and decreased acetylation at position 2 of Xylp in the dimethyl sulfoxide-extracted xylan. This did not affect plant growth but decreased xylose and increased glucose contents in the noncellulosic monosaccharide fraction, and increased glucose and xylose yields of wood enzymatic hydrolysis without pretreatment. Both RWA clades regulate wood xylan acetylation in aspen and are promising targets to improve wood saccharification.},
	language = {en},
	number = {4},
	urldate = {2021-06-07},
	journal = {New Phytologist},
	author = {Pawar, Prashant Mohan-Anupama and Ratke, Christine and Balasubramanian, Vimal K. and Chong, Sun-Li and Gandla, Madhavi Latha and Adriasola, Mathilda and Sparrman, Tobias and Hedenström, Mattias and Szwaj, Klaudia and Derba-Maceluch, Marta and Gaertner, Cyril and Mouille, Gregory and Ezcurra, Ines and Tenkanen, Maija and Jönsson, Leif J. and Mellerowicz, Ewa J.},
	year = {2017},
	note = {\_eprint: https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/nph.14489},
	keywords = {Cas1p, Populus, REDUCED CELL WALL ACETYLATION, saccharification, wood acetylation, xylan, xylan acetylation, xylem},
	pages = {1491--1505},
}

High acetylation of angiosperm wood hinders its conversion to sugars by glycoside hydrolases, subsequent ethanol fermentation and (hence) its use for biofuel production. We studied the REDUCED WALL ACETYLATION (RWA) gene family of the hardwood model Populus to evaluate its potential for improving saccharification. The family has two clades, AB and CD, containing two genes each. All four genes are expressed in developing wood but only RWA-A and -B are activated by master switches of the secondary cell wall PtNST1 and PtMYB21. Histochemical analysis of promoter::GUS lines in hybrid aspen (Populus tremula × tremuloides) showed activation of RWA-A and -B promoters in the secondary wall formation zone, while RWA-C and -D promoter activity was diffuse. Ectopic downregulation of either clade reduced wood xylan and xyloglucan acetylation. Suppressing both clades simultaneously using the wood-specific promoter reduced wood acetylation by 25% and decreased acetylation at position 2 of Xylp in the dimethyl sulfoxide-extracted xylan. This did not affect plant growth but decreased xylose and increased glucose contents in the noncellulosic monosaccharide fraction, and increased glucose and xylose yields of wood enzymatic hydrolysis without pretreatment. Both RWA clades regulate wood xylan acetylation in aspen and are promising targets to improve wood saccharification.

@article{pawar_downregulation_2017-1,
	title = {Downregulation of {\textless}span style="font-variant:small-caps;"{\textgreater}{RWA}{\textless}/span{\textgreater} genes in hybrid aspen affects xylan acetylation and wood saccharification},
	volume = {214},
	issn = {0028-646X, 1469-8137},
	shorttitle = {Downregulation of {\textless}span style="font-variant},
	url = {https://onlinelibrary.wiley.com/doi/10.1111/nph.14489},
	doi = {10.1111/nph.14489},
	language = {en},
	number = {4},
	urldate = {2021-06-07},
	journal = {New Phytologist},
	author = {Pawar, Prashant Mohan‐Anupama and Ratke, Christine and Balasubramanian, Vimal K. and Chong, Sun‐Li and Gandla, Madhavi Latha and Adriasola, Mathilda and Sparrman, Tobias and Hedenström, Mattias and Szwaj, Klaudia and Derba‐Maceluch, Marta and Gaertner, Cyril and Mouille, Gregory and Ezcurra, Ines and Tenkanen, Maija and Jönsson, Leif J. and Mellerowicz, Ewa J.},
	month = jun,
	year = {2017},
	pages = {1491--1505},
}

@article{pawar_muro_2017,
	title = {In muro deacetylation of xylan affects lignin properties and improves saccharification of aspen wood},
	volume = {10},
	issn = {1754-6834},
	url = {http://biotechnologyforbiofuels.biomedcentral.com/articles/10.1186/s13068-017-0782-4},
	doi = {10.1186/s13068-017-0782-4},
	language = {en},
	number = {1},
	urldate = {2021-06-07},
	journal = {Biotechnology for Biofuels},
	author = {Pawar, Prashant Mohan-Anupama and Derba-Maceluch, Marta and Chong, Sun-Li and Gandla, Madhavi Latha and Bashar, Shamrat Shafiul and Sparrman, Tobias and Ahvenainen, Patrik and Hedenström, Mattias and Özparpucu, Merve and Rüggeberg, Markus and Serimaa, Ritva and Lawoko, Martin and Tenkanen, Maija and Jönsson, Leif J. and Mellerowicz, Ewa J.},
	month = dec,
	year = {2017},
	pages = {98},
}

@article{majda_mechanochemical_2017,
	title = {Mechanochemical {Polarization} of {Contiguous} {Cell} {Walls} {Shapes} {Plant} {Pavement} {Cells}},
	volume = {43},
	issn = {15345807},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S1534580717308304},
	doi = {10/gcjnxj},
	language = {en},
	number = {3},
	urldate = {2021-06-07},
	journal = {Developmental Cell},
	author = {Majda, Mateusz and Grones, Peter and Sintorn, Ida-Maria and Vain, Thomas and Milani, Pascale and Krupinski, Pawel and Zagórska-Marek, Beata and Viotti, Corrado and Jönsson, Henrik and Mellerowicz, Ewa J. and Hamant, Olivier and Robert, Stéphanie},
	month = nov,
	year = {2017},
	pages = {290--304.e4},
}

@article{fernandez-moreno_efficient_2016,
	title = {An efficient method for medium throughput screening of cuticular wax composition in different plant species},
	volume = {12},
	issn = {1573-3882, 1573-3890},
	url = {http://link.springer.com/10.1007/s11306-016-0982-0},
	doi = {10.1007/s11306-016-0982-0},
	language = {en},
	number = {4},
	urldate = {2021-06-07},
	journal = {Metabolomics},
	author = {Fernandez-Moreno, Josefina-Patricia and Malitsky, Sergey and Lashbrooke, Justin and Biswal, Ajaya Kumar and Racovita, Radu C. and Mellerowicz, Ewa J. and Jetter, Reinhard and Orzaez, Diego and Aharoni, Asaph and Granell, Antonio},
	month = apr,
	year = {2016},
	pages = {73},
}

@article{pawar_expression_2016,
	title = {Expression of fungal acetyl xylan esterase in \textit{{Arabidopsis} thaliana} improves saccharification of stem lignocellulose},
	volume = {14},
	issn = {14677644},
	url = {http://doi.wiley.com/10.1111/pbi.12393},
	doi = {10.1111/pbi.12393},
	language = {en},
	number = {1},
	urldate = {2021-06-07},
	journal = {Plant Biotechnology Journal},
	author = {Pawar, Prashant Mohan-Anupama and Derba-Maceluch, Marta and Chong, Sun-Li and Gómez, Leonardo D. and Miedes, Eva and Banasiak, Alicja and Ratke, Christine and Gaertner, Cyril and Mouille, Grégory and McQueen-Mason, Simon J. and Molina, Antonio and Sellstedt, Anita and Tenkanen, Maija and Mellerowicz, Ewa J.},
	month = jan,
	year = {2016},
	pages = {387--397},
}

@article{chen_genetic_2016,
	title = {Genetic analysis of fiber dimensions and their correlation with stem diameter and solid-wood properties in {Norway} spruce},
	volume = {12},
	issn = {1614-2942, 1614-2950},
	url = {http://link.springer.com/10.1007/s11295-016-1065-0},
	doi = {10.1007/s11295-016-1065-0},
	language = {en},
	number = {6},
	urldate = {2021-06-07},
	journal = {Tree Genetics \& Genomes},
	author = {Chen, Zhi-Qiang and Karlsson, Bo and Mörling, Tommy and Olsson, Lars and Mellerowicz, Ewa J. and Wu, Harry X. and Lundqvist, Sven-Olof and Gil, María Rosario García},
	month = dec,
	year = {2016},
	pages = {123},
}

@article{chen_method_2016,
	title = {Method for accurate fiber length determination from increment cores for large-scale population analyses in {Norway} spruce},
	volume = {70},
	issn = {1437-434X, 0018-3830},
	url = {https://www.degruyter.com/document/doi/10.1515/hf-2015-0138/html},
	doi = {10/f3rwht},
	abstract = {Abstract
            
              Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce (
              Picea abies
              (L.) Karst) trees on fibers from rings 8–11 (counted from pith), representing juvenile wood of interest in breeding programs. The EM-estimates provided mean-fiber-lengths with bias of only +2.7\% and low scatter. Length-weighing and length
              2
              -weighing gave biases of -7.3\% and +9.3\%, respectively, and larger scatter. The suggested EM approach constitutes a more accurate non-destructive method for fiber length (FL) determination, expected to be applicable also to other conifers.},
	number = {9},
	urldate = {2021-06-07},
	journal = {Holzforschung},
	author = {Chen, Zhi-Qiang and Abramowicz, Konrad and Raczkowski, Rafal and Ganea, Stefana and Wu, Harry X. and Lundqvist, Sven-Olof and Mörling, Tommy and de Luna, Sara Sjöstedt and García Gil, María Rosario and Mellerowicz, Ewa J.},
	month = sep,
	year = {2016},
	pages = {829--838},
}

Abstract Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce ( Picea abies (L.) Karst) trees on fibers from rings 8–11 (counted from pith), representing juvenile wood of interest in breeding programs. The EM-estimates provided mean-fiber-lengths with bias of only +2.7% and low scatter. Length-weighing and length 2 -weighing gave biases of -7.3% and +9.3%, respectively, and larger scatter. The suggested EM approach constitutes a more accurate non-destructive method for fiber length (FL) determination, expected to be applicable also to other conifers.

@article{krzeslowska_pectinous_2016,
	title = {Pectinous cell wall thickenings formation – {A} common defense strategy of plants to cope with {Pb}},
	volume = {214},
	issn = {02697491},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0269749116302858},
	doi = {10.1016/j.envpol.2016.04.019},
	language = {en},
	urldate = {2021-06-07},
	journal = {Environmental Pollution},
	author = {Krzesłowska, Magdalena and Rabęda, Irena and Basińska, Aneta and Lewandowski, Michał and Mellerowicz, Ewa J. and Napieralska, Anna and Samardakiewicz, Sławomir and Woźny, Adam},
	month = jul,
	year = {2016},
	pages = {354--361},
}

@article{chong_active_2015,
	title = {Active fungal {GH115} alpha-glucuronidase produced in {Arabidopsis} thaliana affects only the {UX1}-reactive glucuronate decorations on native glucuronoxylans},
	volume = {15},
	issn = {1472-6750 (Electronic) 1472-6750 (Linking)},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/26084671},
	doi = {10.1186/s12896-015-0154-8},
	abstract = {BACKGROUND: Expressing microbial polysaccharide-modifying enzymes in plants is an attractive approach to custom tailor plant lignocellulose and to study the importance of wall structures to plant development. Expression of alpha-glucuronidases in plants to modify the structures of glucuronoxylans has not been yet attempted. Glycoside hydrolase (GH) family 115 alpha-glucuronidases cleave the internal alpha-D-(4-O-methyl)glucopyranosyluronic acid ((Me)GlcA) from xylans or xylooligosaccharides. In this work, a GH115 alpha-glucuronidase from Schizophyllum commune, ScAGU115, was expressed in Arabidopsis thaliana and targeted to apoplast. The transgene effects on native xylans' structures, plant development, and lignocellulose saccharification were evaluated and compared to those of knocked out glucuronyltransferases AtGUX1 and AtGUX2. RESULTS: The ScAGU115 extracted from cell walls of Arabidopsis was active on the internally substituted aldopentaouronic acid (XUXX). The transgenic plants did not show any change in growth or in lignocellulose saccharification. The cell wall (Me)GlcA and other non-cellulosic sugars, as well as the lignin content, remained unchanged. In contrast, the gux1gux2 double mutant showed a 70\% decrease in (Me)GlcA to xylose molar ratio, and, interestingly, a 60\% increase in the xylose content. Whereas ScAGU115-expressing plants exhibited a decreased signal in native secondary walls from the monoclonal antibody UX1 that recognizes (Me)GlcA on non-acetylated xylan, the signal was not affected after wall deacetylation. In contrast, gux1gux2 mutant was lacking UX1 signals in both native and deacetylated cell walls. This indicates that acetyl substitution on the xylopyranosyl residue carrying (Me)GlcA or on the neighboring xylopyranosyl residues may restrict post-synthetic modification of xylans by ScAGU115 in planta. CONCLUSIONS: Active GH115 alpha-glucuronidase has been produced for the first time in plants. The cell wall-targeted ScAGU115 was shown to affect those glucuronate substitutions of xylan, which are accessible to UX1 antibody and constitute a small fraction in Arabidopsis, whereas majority of (Me)GlcA substitutions were resistant, most likely due to the shielding by acetyl groups. Plants expressing ScAGU115 did not show any defects under laboratory conditions indicating that the UX1 epitope of xylan is not essential under these conditions. Moreover the removal of the UX1 xylan epitope does not affect lignocellulose saccharification.},
	language = {en},
	number = {1},
	urldate = {2021-06-07},
	journal = {BMC Biotechnol},
	author = {Chong, S. L. and Derba-Maceluch, M. and Koutaniemi, S. and Gomez, L. D. and McQueen-Mason, S. J. and Tenkanen, M. and Mellerowicz, E. J.},
	month = jun,
	year = {2015},
	note = {Edition: 2015/06/19},
	keywords = {Arabidopsis Proteins/genetics/metabolism, Arabidopsis/enzymology, Cell Wall/enzymology, Gene Expression Regulation, Enzymologic, Glucuronates/metabolism, Glucuronic Acid/metabolism, Glycoside Hydrolases/*biosynthesis/genetics, Glycosyltransferases/genetics/metabolism, Lignin/genetics/*metabolism, Oligosaccharides/metabolism, Polysaccharides/metabolism, Schizophyllum/*enzymology, Xylans/*metabolism},
	pages = {56},
}

BACKGROUND: Expressing microbial polysaccharide-modifying enzymes in plants is an attractive approach to custom tailor plant lignocellulose and to study the importance of wall structures to plant development. Expression of alpha-glucuronidases in plants to modify the structures of glucuronoxylans has not been yet attempted. Glycoside hydrolase (GH) family 115 alpha-glucuronidases cleave the internal alpha-D-(4-O-methyl)glucopyranosyluronic acid ((Me)GlcA) from xylans or xylooligosaccharides. In this work, a GH115 alpha-glucuronidase from Schizophyllum commune, ScAGU115, was expressed in Arabidopsis thaliana and targeted to apoplast. The transgene effects on native xylans' structures, plant development, and lignocellulose saccharification were evaluated and compared to those of knocked out glucuronyltransferases AtGUX1 and AtGUX2. RESULTS: The ScAGU115 extracted from cell walls of Arabidopsis was active on the internally substituted aldopentaouronic acid (XUXX). The transgenic plants did not show any change in growth or in lignocellulose saccharification. The cell wall (Me)GlcA and other non-cellulosic sugars, as well as the lignin content, remained unchanged. In contrast, the gux1gux2 double mutant showed a 70% decrease in (Me)GlcA to xylose molar ratio, and, interestingly, a 60% increase in the xylose content. Whereas ScAGU115-expressing plants exhibited a decreased signal in native secondary walls from the monoclonal antibody UX1 that recognizes (Me)GlcA on non-acetylated xylan, the signal was not affected after wall deacetylation. In contrast, gux1gux2 mutant was lacking UX1 signals in both native and deacetylated cell walls. This indicates that acetyl substitution on the xylopyranosyl residue carrying (Me)GlcA or on the neighboring xylopyranosyl residues may restrict post-synthetic modification of xylans by ScAGU115 in planta. CONCLUSIONS: Active GH115 alpha-glucuronidase has been produced for the first time in plants. The cell wall-targeted ScAGU115 was shown to affect those glucuronate substitutions of xylan, which are accessible to UX1 antibody and constitute a small fraction in Arabidopsis, whereas majority of (Me)GlcA substitutions were resistant, most likely due to the shielding by acetyl groups. Plants expressing ScAGU115 did not show any defects under laboratory conditions indicating that the UX1 epitope of xylan is not essential under these conditions. Moreover the removal of the UX1 xylan epitope does not affect lignocellulose saccharification.

@article{gorshkova_aspen_2015,
	title = {Aspen {Tension} {Wood} {Fibers} {Contain} beta-(1---{\textgreater} 4)-{Galactans} and {Acidic} {Arabinogalactans} {Retained} by {Cellulose} {Microfibrils} in {Gelatinous} {Walls}},
	volume = {169},
	issn = {1532-2548 (Electronic) 0032-0889 (Linking)},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/26378099},
	doi = {10.1104/pp.15.00690},
	abstract = {Contractile cell walls are found in various plant organs and tissues such as tendrils, contractile roots, and tension wood. The tension-generating mechanism is not known but is thought to involve special cell wall architecture. We previously postulated that tension could result from the entrapment of certain matrix polymers within cellulose microfibrils. As reported here, this hypothesis was corroborated by sequential extraction and analysis of cell wall polymers that are retained by cellulose microfibrils in tension wood and normal wood of hybrid aspen (Populus tremula x Populus tremuloides). beta-(1--{\textgreater}4)-Galactan and type II arabinogalactan were the main large matrix polymers retained by cellulose microfibrils that were specifically found in tension wood. Xyloglucan was detected mostly in oligomeric form in the alkali-labile fraction and was enriched in tension wood. beta-(1--{\textgreater}4)-Galactan and rhamnogalacturonan I backbone epitopes were localized in the gelatinous cell wall layer. Type II arabinogalactans retained by cellulose microfibrils had a higher content of (methyl)glucuronic acid and galactose in tension wood than in normal wood. Thus, beta-(1--{\textgreater}4)-galactan and a specialized form of type II arabinogalactan are trapped by cellulose microfibrils specifically in tension wood and, thus, are the main candidate polymers for the generation of tensional stresses by the entrapment mechanism. We also found high beta-galactosidase activity accompanying tension wood differentiation and propose a testable hypothesis that such activity might regulate galactan entrapment and, thus, mechanical properties of cell walls in tension wood.},
	language = {en},
	number = {3},
	urldate = {2021-06-07},
	journal = {Plant Physiol},
	author = {Gorshkova, T. and Mokshina, N. and Chernova, T. and Ibragimova, N. and Salnikov, V. and Mikshina, P. and Tryfona, T. and Banasiak, A. and Immerzeel, P. and Dupree, P. and Mellerowicz, E. J.},
	month = nov,
	year = {2015},
	note = {Edition: 2015/09/18},
	keywords = {*Models, Biological, Biopolymers/chemistry/metabolism, Cell Wall/chemistry/metabolism, Cellulose/chemistry/*metabolism, Galactans/chemistry/*metabolism, Galactose/metabolism, Gelatin/chemistry/metabolism, Glucans/chemistry/metabolism, Microfibrils/chemistry/*metabolism, Pectins/chemistry/metabolism, Polysaccharides/chemistry/*metabolism, Populus/chemistry/cytology/*metabolism, Wood/chemistry/cytology/metabolism, Xylans/chemistry/metabolism, beta-Galactosidase/metabolism},
	pages = {2048--63},
}

Contractile cell walls are found in various plant organs and tissues such as tendrils, contractile roots, and tension wood. The tension-generating mechanism is not known but is thought to involve special cell wall architecture. We previously postulated that tension could result from the entrapment of certain matrix polymers within cellulose microfibrils. As reported here, this hypothesis was corroborated by sequential extraction and analysis of cell wall polymers that are retained by cellulose microfibrils in tension wood and normal wood of hybrid aspen (Populus tremula x Populus tremuloides). beta-(1–\textgreater4)-Galactan and type II arabinogalactan were the main large matrix polymers retained by cellulose microfibrils that were specifically found in tension wood. Xyloglucan was detected mostly in oligomeric form in the alkali-labile fraction and was enriched in tension wood. beta-(1–\textgreater4)-Galactan and rhamnogalacturonan I backbone epitopes were localized in the gelatinous cell wall layer. Type II arabinogalactans retained by cellulose microfibrils had a higher content of (methyl)glucuronic acid and galactose in tension wood than in normal wood. Thus, beta-(1–\textgreater4)-galactan and a specialized form of type II arabinogalactan are trapped by cellulose microfibrils specifically in tension wood and, thus, are the main candidate polymers for the generation of tensional stresses by the entrapment mechanism. We also found high beta-galactosidase activity accompanying tension wood differentiation and propose a testable hypothesis that such activity might regulate galactan entrapment and, thus, mechanical properties of cell walls in tension wood.

@article{rabeda_colocalization_2015,
	title = {Colocalization of low-methylesterified pectins and {Pb} deposits in the apoplast of aspen roots exposed to lead},
	volume = {205},
	issn = {1873-6424 (Electronic) 0269-7491 (Linking)},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/26123720},
	doi = {10.1016/j.envpol.2015.05.048},
	abstract = {Low-methylesterified homogalacturonans have been suggested to play a role in the binding and immobilization of Pb in CW. Using root apices of hybrid aspen, a plant with a high phytoremediation potential, as a model, we demonstrated that the in situ distribution pattern of low-methylesterified homogalacturonan, pectin epitope (JIM5-P), reflects the pattern of Pb occurrence. The region which indicated high JIM5-P level corresponded with "Pb accumulation zone". Moreover, JIM5-P was especially abundant in cell junctions, CWs lining the intercellular spaces and the corners of intercellular spaces indicating the highest accumulation of Pb. Furthermore, JIM5-P and Pb commonly co-localized. The observations indicate that low-methylesterified homogalacturonan is the CW polymer that determines the capacity of CW for Pb sequestration. Our results suggest a promising directions for CW modification for enhancing the efficiency of plant roots in Pb accumulation, an important aspect in the phytoremediation of soils contaminated with trace metals.},
	language = {en},
	urldate = {2021-06-07},
	journal = {Environ Pollut},
	author = {Rabeda, I. and Bilski, H. and Mellerowicz, E. J. and Napieralska, A. and Suski, S. and Wozny, A. and Krzeslowska, M.},
	month = oct,
	year = {2015},
	note = {Edition: 2015/07/01},
	keywords = {Antibodies, Monoclonal/metabolism, Biodegradation, Environmental, Biomarkers/blood, Cell wall, Esterification, Heavy metal, Lead/*metabolism, Pectins/*metabolism, Phytoremediation, Plant Roots/metabolism, Populus, Populus/*metabolism, Soil Pollutants/*metabolism, Tolerance},
	pages = {315--26},
}

Low-methylesterified homogalacturonans have been suggested to play a role in the binding and immobilization of Pb in CW. Using root apices of hybrid aspen, a plant with a high phytoremediation potential, as a model, we demonstrated that the in situ distribution pattern of low-methylesterified homogalacturonan, pectin epitope (JIM5-P), reflects the pattern of Pb occurrence. The region which indicated high JIM5-P level corresponded with "Pb accumulation zone". Moreover, JIM5-P was especially abundant in cell junctions, CWs lining the intercellular spaces and the corners of intercellular spaces indicating the highest accumulation of Pb. Furthermore, JIM5-P and Pb commonly co-localized. The observations indicate that low-methylesterified homogalacturonan is the CW polymer that determines the capacity of CW for Pb sequestration. Our results suggest a promising directions for CW modification for enhancing the efficiency of plant roots in Pb accumulation, an important aspect in the phytoremediation of soils contaminated with trace metals.

@article{latha_gandla_expression_2015,
	title = {Expression of a fungal glucuronoyl esterase in {Populus}: effects on wood properties and saccharification efficiency},
	volume = {112},
	issn = {1873-3700 (Electronic) 0031-9422 (Linking)},
	shorttitle = {Expression of a fungal glucuronoyl esterase in {Populus}},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/24997793},
	doi = {10.1016/j.phytochem.2014.06.002},
	abstract = {The secondary walls of angiosperms contain large amounts of glucuronoxylan that is thought to be covalently linked to lignin via ester bonds between 4-O-methyl-alpha-D-glucuronic acid (4-O-Me-GlcA) moieties in glucuronoxylan and alcohol groups in lignin. This linkage is proposed to be hydrolysed by glucuronoyl esterases (GCEs) secreted by wood-degrading fungi. We report effects of overexpression of a GCE from the white-rot basidiomycete Phanerochaete carnosa, PcGCE, in hybrid aspen (Populus tremula L. x tremuloides Michx.) on the wood composition and the saccharification efficiency. The recombinant enzyme, which was targeted to the plant cell wall using the signal peptide from hybrid aspen cellulase PttCel9B3, was constitutively expressed resulting in the appearance of GCE activity in protein extracts from developing wood. Diffuse reflectance FT-IR spectroscopy and pyrolysis-GC/MS analyses showed significant alternation in wood chemistry of transgenic plants including an increase in lignin content and S/G ratio, and a decrease in carbohydrate content. Sequential wood extractions confirmed a massive (+43\%) increase of Klason lignin, which was accompanied by a ca. 5\% decrease in cellulose, and ca. 20\% decrease in wood extractives. Analysis of the monosaccharide composition using methanolysis showed a reduction of 4-O-Me-GlcA content without a change in Xyl contents in transgenic lines, suggesting that the covalent links between 4-O-Me-GlcA moieties and lignin protect these moieties from degradation. Enzymatic saccharification without pretreatment resulted in significant decreases of the yields of Gal, Glc, Xyl and Man in transgenic lines, consistent with their increased recalcitrance caused by the increased lignin content. In contrast, the enzymatic saccharification after acid pretreatment resulted in Glc yields similar to wild-type despite of their lower cellulose content. These data indicate that whereas PcGCE expression in hybrid aspen increases lignin deposition, the inhibitory effects of lignin are efficiently removed during acid pretreatment, and the extent of wood cellulose conversion during hydrolysis after acid pretreatment is improved in the transgenic lines possible due to reduced cell wall cross-links between cell wall biopolymers by PcGCE.},
	language = {en},
	urldate = {2021-06-07},
	journal = {Phytochemistry},
	author = {Latha Gandla, M. and Derba-Maceluch, M. and Liu, X. and Gerber, L. and Master, E. R. and Mellerowicz, E. J. and Jonsson, L. J.},
	month = apr,
	year = {2015},
	note = {Edition: 2014/07/07},
	keywords = {Ce15, Enzymatic saccharification, Esterases/*genetics/metabolism, Gene Expression, Glucuronic Acid/*metabolism, Glucuronoyl esterase, Hybrid aspen, Hydrolysis, Phanerochaete/*enzymology/*genetics, Polysaccharides/metabolism, Populus, Populus/*genetics, Secondary cell wall, Wood/*chemistry/*metabolism},
	pages = {210--20},
}

The secondary walls of angiosperms contain large amounts of glucuronoxylan that is thought to be covalently linked to lignin via ester bonds between 4-O-methyl-alpha-D-glucuronic acid (4-O-Me-GlcA) moieties in glucuronoxylan and alcohol groups in lignin. This linkage is proposed to be hydrolysed by glucuronoyl esterases (GCEs) secreted by wood-degrading fungi. We report effects of overexpression of a GCE from the white-rot basidiomycete Phanerochaete carnosa, PcGCE, in hybrid aspen (Populus tremula L. x tremuloides Michx.) on the wood composition and the saccharification efficiency. The recombinant enzyme, which was targeted to the plant cell wall using the signal peptide from hybrid aspen cellulase PttCel9B3, was constitutively expressed resulting in the appearance of GCE activity in protein extracts from developing wood. Diffuse reflectance FT-IR spectroscopy and pyrolysis-GC/MS analyses showed significant alternation in wood chemistry of transgenic plants including an increase in lignin content and S/G ratio, and a decrease in carbohydrate content. Sequential wood extractions confirmed a massive (+43%) increase of Klason lignin, which was accompanied by a ca. 5% decrease in cellulose, and ca. 20% decrease in wood extractives. Analysis of the monosaccharide composition using methanolysis showed a reduction of 4-O-Me-GlcA content without a change in Xyl contents in transgenic lines, suggesting that the covalent links between 4-O-Me-GlcA moieties and lignin protect these moieties from degradation. Enzymatic saccharification without pretreatment resulted in significant decreases of the yields of Gal, Glc, Xyl and Man in transgenic lines, consistent with their increased recalcitrance caused by the increased lignin content. In contrast, the enzymatic saccharification after acid pretreatment resulted in Glc yields similar to wild-type despite of their lower cellulose content. These data indicate that whereas PcGCE expression in hybrid aspen increases lignin deposition, the inhibitory effects of lignin are efficiently removed during acid pretreatment, and the extent of wood cellulose conversion during hydrolysis after acid pretreatment is improved in the transgenic lines possible due to reduced cell wall cross-links between cell wall biopolymers by PcGCE.

@article{chong_glucuronic_2015,
	title = {Glucuronic acid in {Arabidopsis} thaliana xylans carries a novel pentose substituent},
	volume = {79},
	issn = {1879-0003 (Electronic) 0141-8130 (Linking)},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/26047894},
	doi = {10/f3pws3},
	abstract = {Glucuronic acids in Arabidopsis thaliana xylans exist in 4-O-methylated (MeGlcA) and non-methylated (GlcA) forms at a ratio of about 3:2. The matrix-assisted laser desorption/ionization mass spectrometry analysis of the endoxylanase liberated acidic oligosaccharides from the Arabidopsis inflorescence stem showed that two peaks with GlcA (GlcA-Xyl4Ac1 and GlcA-Xyl5Ac2) had abnormally high intensities, as well as different tandem mass spectra, than their 4-O-methylated counterparts. These peaks were interestingly enriched in the xylan biosynthesis mutant irx7 and irx9-1. Multi-stages fragmentation analysis using negative ion electrospray-ion trap mass spectrometry indicated that this GlcA was further carrying a pentose residue in the glucuronoxylan-derived oligosaccharide from irx9-1. The structure was also identified in Arabidopsis wild type. The results prove evidence of a new pentose substitution on the GlcA residue of Arabidopsis GX, which is likely present in the primary walls.},
	language = {en},
	urldate = {2021-06-07},
	journal = {Int J Biol Macromol},
	author = {Chong, S. L. and Koutaniemi, S. and Juvonen, M. and Derba-Maceluch, M. and Mellerowicz, E. J. and Tenkanen, M.},
	month = aug,
	year = {2015},
	note = {Edition: 2015/06/07},
	keywords = {Arabidopsis Proteins/chemistry/*genetics, Arabidopsis thaliana, Arabidopsis/*chemistry/genetics, Endo-1,4-beta Xylanases/genetics, Gene Expression Regulation, Plant, Glucuronic Acid/*chemistry/genetics, Glucuronoxylan, Oligosaccharides/chemistry, Pentoses/*chemistry/genetics, Pentosyltransferases/chemistry/*genetics, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Tandem mass spectrometry, Xylans/biosynthesis/chemistry/*genetics},
	pages = {807--12},
}

Glucuronic acids in Arabidopsis thaliana xylans exist in 4-O-methylated (MeGlcA) and non-methylated (GlcA) forms at a ratio of about 3:2. The matrix-assisted laser desorption/ionization mass spectrometry analysis of the endoxylanase liberated acidic oligosaccharides from the Arabidopsis inflorescence stem showed that two peaks with GlcA (GlcA-Xyl4Ac1 and GlcA-Xyl5Ac2) had abnormally high intensities, as well as different tandem mass spectra, than their 4-O-methylated counterparts. These peaks were interestingly enriched in the xylan biosynthesis mutant irx7 and irx9-1. Multi-stages fragmentation analysis using negative ion electrospray-ion trap mass spectrometry indicated that this GlcA was further carrying a pentose residue in the glucuronoxylan-derived oligosaccharide from irx9-1. The structure was also identified in Arabidopsis wild type. The results prove evidence of a new pentose substitution on the GlcA residue of Arabidopsis GX, which is likely present in the primary walls.

@article{ratke_populus_2015,
	title = {Populus {GT43} family members group into distinct sets required for primary and secondary wall xylan biosynthesis and include useful promoters for wood modification},
	volume = {13},
	issn = {1467-7652 (Electronic) 1467-7644 (Linking)},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/25100045},
	doi = {10/f3nk7x},
	abstract = {The plant GT43 protein family includes xylosyltransferases that are known to be required for xylan backbone biosynthesis, but have incompletely understood specificities. RT-qPCR and histochemical (GUS) analyses of expression patterns of GT43 members in hybrid aspen, reported here, revealed that three clades of the family have markedly differing specificity towards secondary wall-forming cells (wood and extraxylary fibres). Intriguingly, GT43A and B genes (corresponding to the Arabidopsis IRX9 clade) showed higher specificity for secondary-walled cells than GT43C and D genes (IRX14 clade), although both IRX9 and IRX14 are required for xylosyltransferase activity. The remaining genes, GT43E, F and G (IRX9-L clade), showed broad expression patterns. Transient transactivation analyses of GT43A and B reporters demonstrated that they are activated by PtxtMYB021 and PNAC085 (master secondary wall switches), mediated in PtxtMYB021 activation by an AC element. The high observed secondary cell wall specificity of GT43B expression prompted tests of the efficiency of its promoter (pGT43B), relative to the CaMV 35S (35S) promoter, for overexpressing a xylan acetyl esterase (CE5) or downregulating REDUCED WALL ACETYLATION (RWA) family genes and thus engineering wood acetylation. CE5 expression was weaker when driven by pGT43B, but it reduced wood acetyl content substantially more efficiently than the 35S promoter. RNAi silencing of the RWA family, which was ineffective using 35S, was achieved when using GT43B promoter. These results show the utility of the GT43B promoter for genetically engineering properties of wood and fibres.},
	language = {en},
	number = {1},
	urldate = {2021-06-07},
	journal = {Plant Biotechnol J},
	author = {Ratke, C. and Pawar, P. M. and Balasubramanian, V. K. and Naumann, M. and Duncranz, M. L. and Derba-Maceluch, M. and Gorzsas, A. and Endo, S. and Ezcurra, I. and Mellerowicz, E. J.},
	month = jan,
	year = {2015},
	note = {Edition: 2014/08/08},
	keywords = {*Genes, Plant, *Multigene Family, *Promoter Regions, Genetic, Cell Wall/*metabolism, Cloning, Molecular, Gene Expression Regulation, Developmental, Gene Expression Regulation, Plant, Genetic Vectors/metabolism, Glucuronidase/metabolism, Plants, Genetically Modified, Populus/*genetics, Transcriptional Activation/genetics, Wood/genetics/*metabolism, Xylans/*biosynthesis, genetic engineering, poplar, secondary wall, transgenic trees, wood development, xylan biosynthesis},
	pages = {26--37},
}

The plant GT43 protein family includes xylosyltransferases that are known to be required for xylan backbone biosynthesis, but have incompletely understood specificities. RT-qPCR and histochemical (GUS) analyses of expression patterns of GT43 members in hybrid aspen, reported here, revealed that three clades of the family have markedly differing specificity towards secondary wall-forming cells (wood and extraxylary fibres). Intriguingly, GT43A and B genes (corresponding to the Arabidopsis IRX9 clade) showed higher specificity for secondary-walled cells than GT43C and D genes (IRX14 clade), although both IRX9 and IRX14 are required for xylosyltransferase activity. The remaining genes, GT43E, F and G (IRX9-L clade), showed broad expression patterns. Transient transactivation analyses of GT43A and B reporters demonstrated that they are activated by PtxtMYB021 and PNAC085 (master secondary wall switches), mediated in PtxtMYB021 activation by an AC element. The high observed secondary cell wall specificity of GT43B expression prompted tests of the efficiency of its promoter (pGT43B), relative to the CaMV 35S (35S) promoter, for overexpressing a xylan acetyl esterase (CE5) or downregulating REDUCED WALL ACETYLATION (RWA) family genes and thus engineering wood acetylation. CE5 expression was weaker when driven by pGT43B, but it reduced wood acetyl content substantially more efficiently than the 35S promoter. RNAi silencing of the RWA family, which was ineffective using 35S, was achieved when using GT43B promoter. These results show the utility of the GT43B promoter for genetically engineering properties of wood and fibres.

@article{derbamaceluch_suppression_2015,
	title = {Suppression of xylan endotransglycosylase \textit{{PtxtXyn10A}} affects cellulose microfibril angle in secondary wall in aspen wood},
	volume = {205},
	issn = {0028-646X, 1469-8137},
	url = {https://onlinelibrary.wiley.com/doi/10.1111/nph.13099},
	doi = {10/f3n8td},
	language = {en},
	number = {2},
	urldate = {2021-06-08},
	journal = {New Phytologist},
	author = {Derba‐Maceluch, Marta and Awano, Tatsuya and Takahashi, Junko and Lucenius, Jessica and Ratke, Christine and Kontro, Inkeri and Busse‐Wicher, Marta and Kosik, Ondrej and Tanaka, Ryo and Winzéll, Anders and Kallas, Åsa and Leśniewska, Joanna and Berthold, Fredrik and Immerzeel, Peter and Teeri, Tuula T. and Ezcurra, Ines and Dupree, Paul and Serimaa, Ritva and Mellerowicz, Ewa J.},
	month = jan,
	year = {2015},
	pages = {666--681},
}

@article{pawar_acetylation_2013,
	title = {Acetylation of woody lignocellulose: significance and regulation},
	volume = {4},
	issn = {1664-462X},
	shorttitle = {Acetylation of woody lignocellulose},
	url = {http://journal.frontiersin.org/article/10.3389/fpls.2013.00118/abstract},
	doi = {10/f236bp},
	urldate = {2021-06-08},
	journal = {Frontiers in Plant Science},
	author = {Pawar, Prashant Mohan-Anupama and Koutaniemi, Sanna and Tenkanen, Maija and Mellerowicz, Ewa J.},
	year = {2013},
}

@article{mahboubi_aspen_2013,
	title = {Aspen {SUCROSE} {TRANSPORTER3} {Allocates} {Carbon} into {Wood} {Fibers}},
	volume = {163},
	issn = {0032-0889, 1532-2548},
	url = {https://academic.oup.com/plphys/article/163/4/1729-1740/6111119},
	doi = {10/f24j68},
	language = {en},
	number = {4},
	urldate = {2021-06-08},
	journal = {PLANT PHYSIOLOGY},
	author = {Mahboubi, A. and Ratke, C. and Gorzsas, A. and Kumar, M. and Mellerowicz, E. J. and Niittylä, T.},
	month = dec,
	year = {2013},
	pages = {1729--1740},
}

@article{manabe_reduced_2013,
	title = {Reduced {Wall} {Acetylation} {Proteins} {Play} {Vital} and {Distinct} {Roles} in {Cell} {Wall} \textit{{O}} -{Acetylation} in {Arabidopsis}},
	volume = {163},
	issn = {1532-2548},
	url = {https://academic.oup.com/plphys/article/163/3/1107/6112718},
	doi = {10/f2zn5j},
	abstract = {Abstract
            The Reduced Wall Acetylation (RWA) proteins are involved in cell wall acetylation in plants. Previously, we described a single mutant, rwa2, which has about 20\% lower level of O-acetylation in leaf cell walls and no obvious growth or developmental phenotype. In this study, we generated double, triple, and quadruple loss-of-function mutants of all four members of the RWA family in Arabidopsis (Arabidopsis thaliana). In contrast to rwa2, the triple and quadruple rwa mutants display severe growth phenotypes revealing the importance of wall acetylation for plant growth and development. The quadruple rwa mutant can be completely complemented with the RWA2 protein expressed under 35S promoter, indicating the functional redundancy of the RWA proteins. Nevertheless, the degree of acetylation of xylan, (gluco)mannan, and xyloglucan as well as overall cell wall acetylation is affected differently in different combinations of triple mutants, suggesting their diversity in substrate preference. The overall degree of wall acetylation in the rwa quadruple mutant was reduced by 63\% compared with the wild type, and histochemical analysis of the rwa quadruple mutant stem indicates defects in cell differentiation of cell types with secondary cell walls.},
	language = {en},
	number = {3},
	urldate = {2021-06-08},
	journal = {Plant Physiology},
	author = {Manabe, Yuzuki and Verhertbruggen, Yves and Gille, Sascha and Harholt, Jesper and Chong, Sun-Li and Pawar, Prashant Mohan-Anupama and Mellerowicz, Ewa J. and Tenkanen, Maija and Cheng, Kun and Pauly, Markus and Scheller, Henrik Vibe},
	month = oct,
	year = {2013},
	pages = {1107--1117},
}

Abstract The Reduced Wall Acetylation (RWA) proteins are involved in cell wall acetylation in plants. Previously, we described a single mutant, rwa2, which has about 20% lower level of O-acetylation in leaf cell walls and no obvious growth or developmental phenotype. In this study, we generated double, triple, and quadruple loss-of-function mutants of all four members of the RWA family in Arabidopsis (Arabidopsis thaliana). In contrast to rwa2, the triple and quadruple rwa mutants display severe growth phenotypes revealing the importance of wall acetylation for plant growth and development. The quadruple rwa mutant can be completely complemented with the RWA2 protein expressed under 35S promoter, indicating the functional redundancy of the RWA proteins. Nevertheless, the degree of acetylation of xylan, (gluco)mannan, and xyloglucan as well as overall cell wall acetylation is affected differently in different combinations of triple mutants, suggesting their diversity in substrate preference. The overall degree of wall acetylation in the rwa quadruple mutant was reduced by 63% compared with the wild type, and histochemical analysis of the rwa quadruple mutant stem indicates defects in cell differentiation of cell types with secondary cell walls.

@article{miedes_xyloglucan_2013,
	title = {Xyloglucan endotransglucosylase/hydrolase ({XTH}) overexpression affects growth and cell wall mechanics in etiolated {Arabidopsis} hypocotyls},
	volume = {64},
	issn = {1460-2431, 0022-0957},
	url = {https://academic.oup.com/jxb/article-lookup/doi/10.1093/jxb/ert107},
	doi = {10/f244cc},
	language = {en},
	number = {8},
	urldate = {2021-06-08},
	journal = {Journal of Experimental Botany},
	author = {Miedes, Eva and Suslov, Dmitry and Vandenbussche, Filip and Kenobi, Kim and Ivakov, Alexander and Van Der Straeten, Dominique and Lorences, Ester P. and Mellerowicz, Ewa J. and Verbelen, Jean-Pierre and Vissenberg, Kris},
	month = may,
	year = {2013},
	pages = {2481--2497},
}

@article{tsai_constitutive_2012,
	title = {Constitutive expression of a fungal glucuronoyl esterase in {Arabidopsis} reveals altered cell wall composition and structure: {Transgenic} expression of {PcGCE} in {Arabidopsis}},
	volume = {10},
	issn = {14677644},
	shorttitle = {Constitutive expression of a fungal glucuronoyl esterase in {Arabidopsis} reveals altered cell wall composition and structure},
	url = {http://doi.wiley.com/10.1111/j.1467-7652.2012.00735.x},
	doi = {10/f2zwvt},
	language = {en},
	number = {9},
	urldate = {2021-06-08},
	journal = {Plant Biotechnology Journal},
	author = {Tsai, Alex Y.-L. and Canam, Thomas and Gorzsás, András and Mellerowicz, Ewa J. and Campbell, Malcolm M. and Master, Emma R.},
	month = dec,
	year = {2012},
	pages = {1077--1087},
}

@article{gorshkova_plant_2012,
	title = {Plant {Fiber} {Formation}: {State} of the {Art}, {Recent} and {Expected} {Progress}, and {Open} {Questions}},
	volume = {31},
	issn = {0735-2689, 1549-7836},
	shorttitle = {Plant {Fiber} {Formation}},
	url = {http://www.tandfonline.com/doi/abs/10.1080/07352689.2011.616096},
	doi = {10/f2z5m4},
	language = {en},
	number = {3},
	urldate = {2021-06-08},
	journal = {Critical Reviews in Plant Sciences},
	author = {Gorshkova, Tatyana and Brutch, Nina and Chabbert, Brigitte and Deyholos, Michael and Hayashi, Takahisa and Lev-Yadun, Simcha and Mellerowicz, Ewa J. and Morvan, Claudine and Neutelings, Godfrey and Pilate, Gilles},
	month = may,
	year = {2012},
	pages = {201--228},
}

@article{mellerowicz_tensional_2012,
	title = {Tensional stress generation in gelatinous fibres: a review and possible mechanism based on cell-wall structure and composition},
	volume = {63},
	issn = {0022-0957, 1460-2431},
	shorttitle = {Tensional stress generation in gelatinous fibres},
	url = {https://academic.oup.com/jxb/article-lookup/doi/10.1093/jxb/err339},
	doi = {10/cn6bx8},
	language = {en},
	number = {2},
	urldate = {2021-06-08},
	journal = {Journal of Experimental Botany},
	author = {Mellerowicz, E. J. and Gorshkova, T. A.},
	month = jan,
	year = {2012},
	pages = {551--565},
}

@article{raiola_pectin_2011,
	title = {Pectin {Methylesterase} {Is} {Induced} in \textit{{Arabidopsis}} upon {Infection} and {Is} {Necessary} for a {Successful} {Colonization} by {Necrotrophic} {Pathogens}},
	volume = {24},
	issn = {0894-0282, 1943-7706},
	url = {https://apsjournals.apsnet.org/doi/10.1094/MPMI-07-10-0157},
	doi = {10/fwswvk},
	abstract = {The ability of bacterial or fungal necrotrophs to produce enzymes capable of degrading pectin is often related to a successful initiation of the infective process. Pectin is synthesized in a highly methylesterified form and is subsequently de-esterified in muro by pectin methylesterase. De-esterification makes pectin more susceptible to the degradation by pectic enzymes such as endopolygalacturonases (endoPG) and pectate lyases secreted by necrotrophic pathogens during the first stages of infection. We show that, upon infection, Pectobacterium carotovorum and Botrytis cinerea induce in Arabidopsis a rapid expression of AtPME3 that acts as a susceptibility factor and is required for the initial colonization of the host tissue.},
	language = {en},
	number = {4},
	urldate = {2021-06-08},
	journal = {Molecular Plant-Microbe Interactions®},
	author = {Raiola, Alessandro and Lionetti, Vincenzo and Elmaghraby, Ibrahim and Immerzeel, Peter and Mellerowicz, Ewa J. and Salvi, Giovanni and Cervone, Felice and Bellincampi, Daniela},
	month = apr,
	year = {2011},
	pages = {432--440},
}

The ability of bacterial or fungal necrotrophs to produce enzymes capable of degrading pectin is often related to a successful initiation of the infective process. Pectin is synthesized in a highly methylesterified form and is subsequently de-esterified in muro by pectin methylesterase. De-esterification makes pectin more susceptible to the degradation by pectic enzymes such as endopolygalacturonases (endoPG) and pectate lyases secreted by necrotrophic pathogens during the first stages of infection. We show that, upon infection, Pectobacterium carotovorum and Botrytis cinerea induce in Arabidopsis a rapid expression of AtPME3 that acts as a susceptibility factor and is required for the initial colonization of the host tissue.

@article{wang_reduced_2011,
	title = {Reduced {Expression} of the {SHORT}-{ROOT} {Gene} {Increases} the {Rates} of {Growth} and {Development} in {Hybrid} {Poplar} and {Arabidopsis}},
	volume = {6},
	issn = {1932-6203},
	url = {https://dx.plos.org/10.1371/journal.pone.0028878},
	doi = {10/cx2jsh},
	language = {en},
	number = {12},
	urldate = {2021-06-08},
	journal = {PLoS ONE},
	author = {Wang, Jiehua and Andersson-Gunnerås, Sara and Gaboreanu, Ioana and Hertzberg, Magnus and Tucker, Matthew R. and Zheng, Bo and Leśniewska, Joanna and Mellerowicz, Ewa J. and Laux, Thomas and Sandberg, Göran and Jones, Brian},
	editor = {Schönbach, Christian},
	month = dec,
	year = {2011},
	pages = {e28878},
}

@article{nishikubo_xyloglucan_2011,
	title = {Xyloglucan \textit{endo} -{Transglycosylase}-{Mediated} {Xyloglucan} {Rearrangements} in {Developing} {Wood} of {Hybrid} {Aspen}},
	volume = {155},
	issn = {1532-2548},
	url = {https://academic.oup.com/plphys/article/155/1/399/6111559},
	doi = {10/fswhm6},
	abstract = {Abstract
            Xyloglucan endo-transglycosylases (XETs) encoded by xyloglucan endo-transglycosylases/hydrolase (XTH) genes modify the xyloglucan-cellulose framework of plant cell walls, thereby regulating their expansion and strength. To evaluate the importance of XET in wood development, we studied xyloglucan dynamics and XTH gene expression in developing wood and modified XET activity in hybrid aspen (Populus tremula × tremuloides) by overexpressing PtxtXET16-34. We show that developmental modifications during xylem differentiation include changes from loosely to tightly bound forms of xyloglucan and increases in the abundance of fucosylated xyloglucan epitope recognized by the CCRC-M1 antibody. We found that at least 16 Populus  XTH genes, all likely encoding XETs, are expressed in developing wood. Five genes were highly and ubiquitously expressed, whereas PtxtXET16-34 was expressed more weakly but specifically in developing wood. Transgenic up-regulation of XET activity induced changes in cell wall xyloglucan, but its effects were dependent on developmental stage. For instance, XET overexpression increased abundance of the CCRC-M1 epitope in cambial cells and xylem cells in early stages of differentiation but not in mature xylem. Correspondingly, an increase in tightly bound xyloglucan content was observed in primary-walled xylem but a decrease was seen in secondary-walled xylem. Thus, in young xylem cells, XET activity limits xyloglucan incorporation into the tightly bound wall network but removes it from cell walls in older cells. XET overexpression promoted vessel element growth but not fiber expansion. We suggest that the amount of nascent xyloglucan relative to XET is an important determinant of whether XET strengthens or loosens the cell wall.},
	language = {en},
	number = {1},
	urldate = {2021-06-08},
	journal = {Plant Physiology},
	author = {Nishikubo, Nobuyuki and Takahashi, Junko and Roos, Alexandra A. and Derba-Maceluch, Marta and Piens, Kathleen and Brumer, Harry and Teeri, Tuula T. and Stålbrand, Henrik and Mellerowicz, Ewa J.},
	month = jan,
	year = {2011},
	pages = {399--413},
}

Abstract Xyloglucan endo-transglycosylases (XETs) encoded by xyloglucan endo-transglycosylases/hydrolase (XTH) genes modify the xyloglucan-cellulose framework of plant cell walls, thereby regulating their expansion and strength. To evaluate the importance of XET in wood development, we studied xyloglucan dynamics and XTH gene expression in developing wood and modified XET activity in hybrid aspen (Populus tremula × tremuloides) by overexpressing PtxtXET16-34. We show that developmental modifications during xylem differentiation include changes from loosely to tightly bound forms of xyloglucan and increases in the abundance of fucosylated xyloglucan epitope recognized by the CCRC-M1 antibody. We found that at least 16 Populus  XTH genes, all likely encoding XETs, are expressed in developing wood. Five genes were highly and ubiquitously expressed, whereas PtxtXET16-34 was expressed more weakly but specifically in developing wood. Transgenic up-regulation of XET activity induced changes in cell wall xyloglucan, but its effects were dependent on developmental stage. For instance, XET overexpression increased abundance of the CCRC-M1 epitope in cambial cells and xylem cells in early stages of differentiation but not in mature xylem. Correspondingly, an increase in tightly bound xyloglucan content was observed in primary-walled xylem but a decrease was seen in secondary-walled xylem. Thus, in young xylem cells, XET activity limits xyloglucan incorporation into the tightly bound wall network but removes it from cell walls in older cells. XET overexpression promoted vessel element growth but not fiber expansion. We suggest that the amount of nascent xyloglucan relative to XET is an important determinant of whether XET strengthens or loosens the cell wall.

@article{nishikubo_xyloglucan_2011,
	title = {Xyloglucan endo-{Transglycosylase}-{Mediated} {Xyloglucan} {Rearrangements} in {Developing} {Wood} of {Hybrid} {Aspen}},
	volume = {155},
	issn = {0032-0889},
	url = {https://doi.org/10.1104/pp.110.166934},
	doi = {10/fswhm6},
	abstract = {Xyloglucan endo-transglycosylases (XETs) encoded by xyloglucan endo-transglycosylases/hydrolase (XTH) genes modify the xyloglucan-cellulose framework of plant cell walls, thereby regulating their expansion and strength. To evaluate the importance of XET in wood development, we studied xyloglucan dynamics and XTH gene expression in developing wood and modified XET activity in hybrid aspen (Populus tremula × tremuloides) by overexpressing PtxtXET16-34. We show that developmental modifications during xylem differentiation include changes from loosely to tightly bound forms of xyloglucan and increases in the abundance of fucosylated xyloglucan epitope recognized by the CCRC-M1 antibody. We found that at least 16 Populus  XTH genes, all likely encoding XETs, are expressed in developing wood. Five genes were highly and ubiquitously expressed, whereas PtxtXET16-34 was expressed more weakly but specifically in developing wood. Transgenic up-regulation of XET activity induced changes in cell wall xyloglucan, but its effects were dependent on developmental stage. For instance, XET overexpression increased abundance of the CCRC-M1 epitope in cambial cells and xylem cells in early stages of differentiation but not in mature xylem. Correspondingly, an increase in tightly bound xyloglucan content was observed in primary-walled xylem but a decrease was seen in secondary-walled xylem. Thus, in young xylem cells, XET activity limits xyloglucan incorporation into the tightly bound wall network but removes it from cell walls in older cells. XET overexpression promoted vessel element growth but not fiber expansion. We suggest that the amount of nascent xyloglucan relative to XET is an important determinant of whether XET strengthens or loosens the cell wall.},
	number = {1},
	urldate = {2021-06-08},
	journal = {Plant Physiology},
	author = {Nishikubo, Nobuyuki and Takahashi, Junko and Roos, Alexandra A. and Derba-Maceluch, Marta and Piens, Kathleen and Brumer, Harry and Teeri, Tuula T. and Stålbrand, Henrik and Mellerowicz, Ewa J.},
	month = jan,
	year = {2011},
	pages = {399--413},
}

Xyloglucan endo-transglycosylases (XETs) encoded by xyloglucan endo-transglycosylases/hydrolase (XTH) genes modify the xyloglucan-cellulose framework of plant cell walls, thereby regulating their expansion and strength. To evaluate the importance of XET in wood development, we studied xyloglucan dynamics and XTH gene expression in developing wood and modified XET activity in hybrid aspen (Populus tremula × tremuloides) by overexpressing PtxtXET16-34. We show that developmental modifications during xylem differentiation include changes from loosely to tightly bound forms of xyloglucan and increases in the abundance of fucosylated xyloglucan epitope recognized by the CCRC-M1 antibody. We found that at least 16 Populus  XTH genes, all likely encoding XETs, are expressed in developing wood. Five genes were highly and ubiquitously expressed, whereas PtxtXET16-34 was expressed more weakly but specifically in developing wood. Transgenic up-regulation of XET activity induced changes in cell wall xyloglucan, but its effects were dependent on developmental stage. For instance, XET overexpression increased abundance of the CCRC-M1 epitope in cambial cells and xylem cells in early stages of differentiation but not in mature xylem. Correspondingly, an increase in tightly bound xyloglucan content was observed in primary-walled xylem but a decrease was seen in secondary-walled xylem. Thus, in young xylem cells, XET activity limits xyloglucan incorporation into the tightly bound wall network but removes it from cell walls in older cells. XET overexpression promoted vessel element growth but not fiber expansion. We suggest that the amount of nascent xyloglucan relative to XET is an important determinant of whether XET strengthens or loosens the cell wall.

@article{takahashi_korrigan1_2009,
	title = {{KORRIGAN1} and its {Aspen} {Homolog} {PttCel9A1} {Decrease} {Cellulose} {Crystallinity} in {Arabidopsis} {Stems}},
	volume = {50},
	issn = {1471-9053, 0032-0781},
	url = {https://academic.oup.com/pcp/article-lookup/doi/10.1093/pcp/pcp062},
	doi = {10/djcxr3},
	language = {en},
	number = {6},
	urldate = {2021-06-08},
	journal = {Plant and Cell Physiology},
	author = {Takahashi, Junko and Rudsander, Ulla J. and Hedenström, Mattias and Banasiak, Alicja and Harholt, Jesper and Amelot, Nicolas and Immerzeel, Peter and Ryden, Peter and Endo, Satoshi and Ibatullin, Farid M. and Brumer, Harry and del Campillo, Elena and Master, Emma R. and Vibe Scheller, Henrik and Sundberg, Björn and Teeri, Tuula T. and Mellerowicz, Ewa J.},
	month = jun,
	year = {2009},
	pages = {1099--1115},
}

@article{meng_udp-glucose_2009,
	title = {{UDP}-{Glucose} {Pyrophosphorylase} is not {Rate} {Limiting}, but is {Essential} in {Arabidopsis}},
	volume = {50},
	issn = {0032-0781, 1471-9053},
	url = {https://academic.oup.com/pcp/article-lookup/doi/10.1093/pcp/pcp052},
	doi = {10/cwnt2d},
	language = {en},
	number = {5},
	urldate = {2021-06-08},
	journal = {Plant and Cell Physiology},
	author = {Meng, M. and Geisler, M. and Johansson, H. and Harholt, J. and Scheller, H. V. and Mellerowicz, E. J. and Kleczkowski, L. A.},
	month = may,
	year = {2009},
	pages = {998--1011},
}

@article{goue_microgenomic_2008,
	title = {Microgenomic analysis reveals cell type‐specific gene expression patterns between ray and fusiform initials within the cambial meristem of \textit{{Populus}}},
	volume = {180},
	issn = {0028-646X, 1469-8137},
	url = {https://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2008.02556.x},
	doi = {10/cpqv9f},
	language = {en},
	number = {1},
	urldate = {2021-06-10},
	journal = {New Phytologist},
	author = {Goué, Nadia and Lesage‐Descauses, Marie‐Claude and Mellerowicz, Ewa J. and Magel, Elisabeth and Label, Philippe and Sundberg, Björn},
	month = oct,
	year = {2008},
	pages = {45--56},
}

@article{siedlecka_pectin_2008,
	title = {Pectin {Methyl} {Esterase} {Inhibits} {Intrusive} and {Symplastic} {Cell} {Growth} in {Developing} {Wood} {Cells} of \textit{{Populus}}},
	volume = {146},
	issn = {1532-2548},
	url = {https://academic.oup.com/plphys/article/146/2/323/6107207},
	doi = {10/bz7b7b},
	abstract = {Abstract
            Wood cells, unlike most other cells in plants, grow by a unique combination of intrusive and symplastic growth. Fibers grow in diameter by diffuse symplastic growth, but they elongate solely by intrusive apical growth penetrating the pectin-rich middle lamella that cements neighboring cells together. In contrast, vessel elements grow in diameter by a combination of intrusive and symplastic growth. We demonstrate that an abundant pectin methyl esterase (PME; EC 3.1.1.11) from wood-forming tissues of hybrid aspen (Populus tremula × tremuloides) acts as a negative regulator of both symplastic and intrusive growth of developing wood cells. When PttPME1 expression was up- and down-regulated in transgenic aspen trees, the PME activity in wood-forming tissues was correspondingly altered. PME removes methyl ester groups from homogalacturonan (HG) and transgenic trees had modified HG methylesterification patterns, as demonstrated by two-dimensional nuclear magnetic resonance and immunostaining using PAM1 and LM7 antibodies. In situ distributions of PAM1 and LM7 epitopes revealed changes in pectin methylesterification in transgenic trees that were specifically localized in expanding wood cells. The results show that en block deesterification of HG by PttPME1 inhibits both symplastic growth and intrusive growth. PttPME1 is therefore involved in mechanisms determining fiber width and length in the wood of aspen trees.},
	language = {en},
	number = {2},
	urldate = {2021-06-10},
	journal = {Plant Physiology},
	author = {Siedlecka, Anna and Wiklund, Susanne and Péronne, Marie-Amélie and Micheli, Fabienne and Leśniewska, Joanna and Sethson, Ingmar and Edlund, Ulf and Richard, Luc and Sundberg, Björn and Mellerowicz, Ewa J.},
	month = feb,
	year = {2008},
	pages = {323--324},
}

Abstract Wood cells, unlike most other cells in plants, grow by a unique combination of intrusive and symplastic growth. Fibers grow in diameter by diffuse symplastic growth, but they elongate solely by intrusive apical growth penetrating the pectin-rich middle lamella that cements neighboring cells together. In contrast, vessel elements grow in diameter by a combination of intrusive and symplastic growth. We demonstrate that an abundant pectin methyl esterase (PME; EC 3.1.1.11) from wood-forming tissues of hybrid aspen (Populus tremula × tremuloides) acts as a negative regulator of both symplastic and intrusive growth of developing wood cells. When PttPME1 expression was up- and down-regulated in transgenic aspen trees, the PME activity in wood-forming tissues was correspondingly altered. PME removes methyl ester groups from homogalacturonan (HG) and transgenic trees had modified HG methylesterification patterns, as demonstrated by two-dimensional nuclear magnetic resonance and immunostaining using PAM1 and LM7 antibodies. In situ distributions of PAM1 and LM7 epitopes revealed changes in pectin methylesterification in transgenic trees that were specifically localized in expanding wood cells. The results show that en block deesterification of HG by PttPME1 inhibits both symplastic growth and intrusive growth. PttPME1 is therefore involved in mechanisms determining fiber width and length in the wood of aspen trees.

@article{wiklund_visualization_2008,
	title = {Visualization of {GC}/{TOF}-{MS}-{Based} {Metabolomics} {Data} for {Identification} of {Biochemically} {Interesting} {Compounds} {Using} {OPLS} {Class} {Models}},
	volume = {80},
	issn = {0003-2700, 1520-6882},
	url = {https://pubs.acs.org/doi/10.1021/ac0713510},
	doi = {10/bjbc4d},
	language = {en},
	number = {1},
	urldate = {2021-06-10},
	journal = {Analytical Chemistry},
	author = {Wiklund, Susanne and Johansson, Erik and Sjöström, Lina and Mellerowicz, Ewa J. and Edlund, Ulf and Shockcor, John P. and Gottfries, Johan and Moritz, Thomas and Trygg, Johan},
	month = jan,
	year = {2008},
	pages = {115--122},
}

@article{mellerowicz_xyloglucan_2008,
	title = {Xyloglucan: {The} {Molecular} {Muscle} of {Trees}},
	volume = {102},
	issn = {1095-8290, 0305-7364},
	shorttitle = {Xyloglucan},
	url = {https://academic.oup.com/aob/article-lookup/doi/10.1093/aob/mcn170},
	doi = {10/d76fhs},
	language = {en},
	number = {5},
	urldate = {2021-06-10},
	journal = {Annals of Botany},
	author = {Mellerowicz, Ewa J. and Immerzeel, Peter and Hayashi, Takahisa},
	month = nov,
	year = {2008},
	pages = {659--665},
}

@article{meng_differential_2007,
	title = {Differential tissue/organ-dependent expression of two sucrose- and cold-responsive genes for {UDP}-glucose pyrophosphorylase in {Populus}},
	volume = {389},
	issn = {03781119},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0378111906007062},
	doi = {10/fn8z4c},
	language = {en},
	number = {2},
	urldate = {2021-06-10},
	journal = {Gene},
	author = {Meng, Meng and Geisler, Matt and Johansson, Henrik and Mellerowicz, Ewa J. and Karpinski, Stanislaw and Kleczkowski, Leszek A.},
	month = mar,
	year = {2007},
	pages = {186--195},
}

@article{gray-mitsumune_ectopic_2007,
	title = {Ectopic expression of a wood-abundant expansin {PttEXPA1} promotes cell expansion in primary and secondary tissues in aspen},
	volume = {0},
	issn = {1467-7644, 1467-7652},
	url = {http://doi.wiley.com/10.1111/j.1467-7652.2007.00295.x},
	doi = {10/cz7ht2},
	language = {en},
	number = {0},
	urldate = {2021-06-10},
	journal = {Plant Biotechnology Journal},
	author = {Gray-Mitsumune, Madoka and Blomquist, Kristina and McQueen-Mason, Simon and Teeri, Tuula T. and Sundberg, Björn and Mellerowicz, Ewa J.},
	month = oct,
	year = {2007},
	pages = {071003005211001--???},
}

@article{andersson-gunneras_biosynthesis_2006,
	title = {Biosynthesis of cellulose-enriched tension wood in {Populus}: global analysis of transcripts and metabolites identifies biochemical and developmental regulators in secondary wall biosynthesis},
	volume = {45},
	issn = {1365-313X},
	shorttitle = {Biosynthesis of cellulose-enriched tension wood in {Populus}},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-313X.2005.02584.x},
	doi = {10/fkwhm3},
	abstract = {Stems and branches of angiosperm trees form tension wood (TW) when exposed to a gravitational stimulus. One of the main characteristics of TW, which distinguishes it from normal wood, is the formation of fibers with a thick inner gelatinous cell wall layer mainly composed of crystalline cellulose. Hence TW is enriched in cellulose, and deficient in lignin and hemicelluloses. An expressed sequence tag library made from TW-forming tissues in Populus tremula (L.) × tremuloides (Michx.) and data from transcript profiling using microarray and metabolite analysis were obtained during TW formation in Populus tremula (L.) in two growing seasons. The data were examined with the aim of identifying the genes responsible for the change in carbon (C) flow into various cell wall components, and the mechanisms important for the formation of the gelatinous cell wall layer (G-layer). A specific effort was made to identify carbohydrate-active enzymes with a putative function in cell wall biosynthesis. An increased C flux to cellulose was suggested by a higher abundance of sucrose synthase transcripts. However, genes related to the cellulose biosynthetic machinery were not generally affected, although the expression of secondary wall-specific CesA genes was modified in both directions. Other pathways for which the data suggested increased activity included lipid and glucosamine biosynthesis and the pectin degradation machinery. In addition, transcripts encoding fasciclin-like arabinogalactan proteins were particularly increased and found to lack true Arabidopsis orthologs. Major pathways for which the transcriptome and metabolome analysis suggested decreased activity were the pathway for C flux through guanosine 5′-diphosphate (GDP) sugars to mannans, the pentose phosphate pathway, lignin biosynthesis, and biosynthesis of cell wall matrix carbohydrates. Several differentially expressed auxin- and ethylene-related genes and transcription factors were also identified.},
	language = {en},
	number = {2},
	urldate = {2021-06-11},
	journal = {The Plant Journal},
	author = {Andersson-Gunnerås, Sara and Mellerowicz, Ewa J. and Love, Jonathan and Segerman, Bo and Ohmiya, Yasunori and Coutinho, Pedro M. and Nilsson, Peter and Henrissat, Bernard and Moritz, Thomas and Sundberg, Björn},
	year = {2006},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.2005.02584.x},
	keywords = {cell walls, cellulose, development, hemicellulose, lignin, poplar},
	pages = {144--165},
}

Stems and branches of angiosperm trees form tension wood (TW) when exposed to a gravitational stimulus. One of the main characteristics of TW, which distinguishes it from normal wood, is the formation of fibers with a thick inner gelatinous cell wall layer mainly composed of crystalline cellulose. Hence TW is enriched in cellulose, and deficient in lignin and hemicelluloses. An expressed sequence tag library made from TW-forming tissues in Populus tremula (L.) × tremuloides (Michx.) and data from transcript profiling using microarray and metabolite analysis were obtained during TW formation in Populus tremula (L.) in two growing seasons. The data were examined with the aim of identifying the genes responsible for the change in carbon (C) flow into various cell wall components, and the mechanisms important for the formation of the gelatinous cell wall layer (G-layer). A specific effort was made to identify carbohydrate-active enzymes with a putative function in cell wall biosynthesis. An increased C flux to cellulose was suggested by a higher abundance of sucrose synthase transcripts. However, genes related to the cellulose biosynthetic machinery were not generally affected, although the expression of secondary wall-specific CesA genes was modified in both directions. Other pathways for which the data suggested increased activity included lipid and glucosamine biosynthesis and the pectin degradation machinery. In addition, transcripts encoding fasciclin-like arabinogalactan proteins were particularly increased and found to lack true Arabidopsis orthologs. Major pathways for which the transcriptome and metabolome analysis suggested decreased activity were the pathway for C flux through guanosine 5′-diphosphate (GDP) sugars to mannans, the pentose phosphate pathway, lignin biosynthesis, and biosynthesis of cell wall matrix carbohydrates. Several differentially expressed auxin- and ethylene-related genes and transcription factors were also identified.

@article{geisler-lee_poplar_2006,
	title = {Poplar carbohydrate-active enzymes. {Gene} identification and expression analyses},
	volume = {140},
	issn = {0032-0889},
	doi = {10/bj9bkd},
	abstract = {Over 1,600 genes encoding carbohydrate-active enzymes (CAZymes) in the Populus trichocarpa (Torr.\&Gray) genome were identified based on sequence homology, annotated, and grouped into families of glycosyltransferases, glycoside hydrolases, carbohydrate esterases, polysaccharide lyases, and expansins. Poplar ( Populus spp.) had approximately 1.6 times more CAZyme genes than Arabidopsis ( Arabidopsis thaliana). Whereas most families were proportionally increased, xylan and pectin-related families were underrepresented and the GT1 family of secondary metabolite-glycosylating enzymes was overrepresented in poplar. CAZyme gene expression in poplar was analyzed using a collection of 100,000 expressed sequence tags from 17 different tissues and compared to microarray data for poplar and Arabidopsis. Expression of genes involved in pectin and hemicellulose metabolism was detected in all tissues, indicating a constant maintenance of transcripts encoding enzymes remodeling the cell wall matrix. The most abundant transcripts encoded sucrose synthases that were specifically expressed in wood-forming tissues along with cellulose synthase and homologs of KORRIGAN and ELP1. Woody tissues were the richest source of various other CAZyme transcripts, demonstrating the importance of this group of enzymes for xylogenesis. In contrast, there was little expression of genes related to starch metabolism during wood formation, consistent with the preferential flux of carbon to cell wall biosynthesis. Seasonally dormant meristems of poplar showed a high prevalence of transcripts related to starch metabolism and surprisingly retained transcripts of some cell wall synthesis enzymes. The data showed profound changes in CAZyme transcriptomes in different poplar tissues and pointed to some key differences in CAZyme genes and their regulation between herbaceous and woody plants.},
	language = {English},
	number = {3},
	journal = {Plant Physiology},
	author = {Geisler-Lee, J. and Geisler, M. and Coutinho, P. M. and Segerman, B. and Nishikubo, N. and Takahashi, J. and Aspeborg, H. and Djerbi, S. and Master, E. and Andersson-Gunneras, S. and Sundberg, B. and Karpinski, S. and Teeri, T. T. and Kleczkowski, L. A. and Henrissat, B. and Mellerowicz, E. J.},
	month = mar,
	year = {2006},
	note = {Place: Rockville
Publisher: Amer Soc Plant Biologists
WOS:000235868900014},
	keywords = {arabidopsis, callose synthase, cell-walls, cellulose, family, hybrid aspen, multiple sequence alignment, pectin methylesterases, populus, sucrose},
	pages = {946--962},
}

Over 1,600 genes encoding carbohydrate-active enzymes (CAZymes) in the Populus trichocarpa (Torr.&Gray) genome were identified based on sequence homology, annotated, and grouped into families of glycosyltransferases, glycoside hydrolases, carbohydrate esterases, polysaccharide lyases, and expansins. Poplar ( Populus spp.) had approximately 1.6 times more CAZyme genes than Arabidopsis ( Arabidopsis thaliana). Whereas most families were proportionally increased, xylan and pectin-related families were underrepresented and the GT1 family of secondary metabolite-glycosylating enzymes was overrepresented in poplar. CAZyme gene expression in poplar was analyzed using a collection of 100,000 expressed sequence tags from 17 different tissues and compared to microarray data for poplar and Arabidopsis. Expression of genes involved in pectin and hemicellulose metabolism was detected in all tissues, indicating a constant maintenance of transcripts encoding enzymes remodeling the cell wall matrix. The most abundant transcripts encoded sucrose synthases that were specifically expressed in wood-forming tissues along with cellulose synthase and homologs of KORRIGAN and ELP1. Woody tissues were the richest source of various other CAZyme transcripts, demonstrating the importance of this group of enzymes for xylogenesis. In contrast, there was little expression of genes related to starch metabolism during wood formation, consistent with the preferential flux of carbon to cell wall biosynthesis. Seasonally dormant meristems of poplar showed a high prevalence of transcripts related to starch metabolism and surprisingly retained transcripts of some cell wall synthesis enzymes. The data showed profound changes in CAZyme transcriptomes in different poplar tissues and pointed to some key differences in CAZyme genes and their regulation between herbaceous and woody plants.

@article{gray-mitsumune_expansins_2004,
	title = {Expansins {Abundant} in {Secondary} {Xylem} {Belong} to {Subgroup} {A} of the α-{Expansin} {Gene} {Family}},
	volume = {135},
	issn = {0032-0889},
	url = {https://doi.org/10.1104/pp.104.039321},
	doi = {10/dd876s},
	abstract = {Differentiation of xylem cells in dicotyledonous plants involves expansion of the radial primary cell walls and intrusive tip growth of cambial derivative cells prior to the deposition of a thick secondary wall essential for xylem function. Expansins are cell wall-residing proteins that have an ability to plasticize the cellulose-hemicellulose network of primary walls. We found expansin activity in proteins extracted from the cambial region of mature stems in a model tree species hybrid aspen (Populus tremula × Populus tremuloides Michx). We identified three α-expansin genes (PttEXP1, PttEXP2, and PttEXP8) and one β-expansin gene (PttEXPB1) in a cambial region expressed sequence tag library, among which PttEXP1 was most abundantly represented. Northern-blot analyses in aspen vegetative organs and tissues showed that PttEXP1 was specifically expressed in mature stems exhibiting secondary growth, where it was present in the cambium and in the radial expansion zone. By contrast, PttEXP2 was mostly expressed in developing leaves. In situ reverse transcription-PCR provided evidence for accumulation of mRNA of PttEXP1 along with ribosomal rRNA at the tips of intrusively growing xylem fibers, suggesting that PttEXP1 protein has a role in intrusive tip growth. An examination of tension wood and leaf cDNA libraries identified another expansin, PttEXP5, very similar to PttEXP1, as the major expansin in developing tension wood, while PttEXP3 was the major expansin expressed in developing leaves. Comparative analysis of expansins expressed in woody stems in aspen, Arabidopsis, and pine showed that the most abundantly expressed expansins share sequence similarities, belonging to the subfamily A of α-expansins and having two conserved motifs at the beginning and end of the mature protein, RIPVG and KNFRV, respectively. This conservation suggests that these genes may share a specialized, not yet identified function.},
	number = {3},
	urldate = {2021-06-15},
	journal = {Plant Physiology},
	author = {Gray-Mitsumune, Madoka and Mellerowicz, Ewa J. and Abe, Hisashi and Schrader, Jarmo and Winzéll, Anders and Sterky, Fredrik and Blomqvist, Kristina and McQueen-Mason, Simon and Teeri, Tuula T. and Sundberg, Björn},
	month = jul,
	year = {2004},
	pages = {1552--1564},
}

Differentiation of xylem cells in dicotyledonous plants involves expansion of the radial primary cell walls and intrusive tip growth of cambial derivative cells prior to the deposition of a thick secondary wall essential for xylem function. Expansins are cell wall-residing proteins that have an ability to plasticize the cellulose-hemicellulose network of primary walls. We found expansin activity in proteins extracted from the cambial region of mature stems in a model tree species hybrid aspen (Populus tremula × Populus tremuloides Michx). We identified three α-expansin genes (PttEXP1, PttEXP2, and PttEXP8) and one β-expansin gene (PttEXPB1) in a cambial region expressed sequence tag library, among which PttEXP1 was most abundantly represented. Northern-blot analyses in aspen vegetative organs and tissues showed that PttEXP1 was specifically expressed in mature stems exhibiting secondary growth, where it was present in the cambium and in the radial expansion zone. By contrast, PttEXP2 was mostly expressed in developing leaves. In situ reverse transcription-PCR provided evidence for accumulation of mRNA of PttEXP1 along with ribosomal rRNA at the tips of intrusively growing xylem fibers, suggesting that PttEXP1 protein has a role in intrusive tip growth. An examination of tension wood and leaf cDNA libraries identified another expansin, PttEXP5, very similar to PttEXP1, as the major expansin in developing tension wood, while PttEXP3 was the major expansin expressed in developing leaves. Comparative analysis of expansins expressed in woody stems in aspen, Arabidopsis, and pine showed that the most abundantly expressed expansins share sequence similarities, belonging to the subfamily A of α-expansins and having two conserved motifs at the beginning and end of the mature protein, RIPVG and KNFRV, respectively. This conservation suggests that these genes may share a specialized, not yet identified function.

@article{gray-mitsumune_liquid_2004,
	title = {Liquid {Phase} {Fluorescence} in situ {RT}-{PCR} {Analysis} for {Gene} {Expression} {Analysis} in {Woody} {Stems}},
	volume = {6},
	issn = {1438-8677},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1055/s-2003-44747},
	doi = {10/bf7fs7},
	abstract = {Abstract: We explore a rapid in situ RT-PCR protocol for gene expression studies in woody stem tissues. In situ RT-PCR was performed using fluorescent dye-conjugated nucleic acid and the fluorescence signals derived from target RNAs were detected using confocal laser scanning microscopy. The signal to background ratio was greatly enhanced by performing two rounds of PCR reactions, first without the fluorescent dye and second with the dye. Using this protocol, we obtained strong gene-specific signals in secondary stem tissues. The signals were PCR-dependent, as shown by the lack of cytoplasmic signals in the tissue sections in which either DNA polymerase or primers were omitted from PCR reactions, and were RNA-dependent, as shown by great reduction of cytoplasmic signals when sections were treated with RNase before RT reactions. To verify our protocol, transcript localization of the rbcS gene was examined in secondary stems of hybrid aspen (Populus tremula L. ×tremuloides Michx.) and compared to the chlorophyll autofluorescence signal. The in situ RT-PCR signals form the rbcS gene and chlorophyll autofluorescence co-localized in the same cell types. The signal was also confirmed by Northern blot analysis of isolated RNA from the cambium and developing xylem, thus confirming the validity of the protocol. Some difficulties of in situ transcript localization and the interpretation of the signal distribution in the secondary tissues are discussed.},
	language = {en},
	number = {1},
	urldate = {2021-06-15},
	journal = {Plant Biology},
	author = {Gray-Mitsumune, M. and Abe, H. and Takahashi, J. and Sundberg, B. and Mellerowicz, E. J.},
	year = {2004},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1055/s-2003-44747},
	keywords = {Confocal laser scanning microscopy, Populus, in situ RT-PCR, vascular cambium, wood, xylem},
	pages = {47--54},
}

Abstract: We explore a rapid in situ RT-PCR protocol for gene expression studies in woody stem tissues. In situ RT-PCR was performed using fluorescent dye-conjugated nucleic acid and the fluorescence signals derived from target RNAs were detected using confocal laser scanning microscopy. The signal to background ratio was greatly enhanced by performing two rounds of PCR reactions, first without the fluorescent dye and second with the dye. Using this protocol, we obtained strong gene-specific signals in secondary stem tissues. The signals were PCR-dependent, as shown by the lack of cytoplasmic signals in the tissue sections in which either DNA polymerase or primers were omitted from PCR reactions, and were RNA-dependent, as shown by great reduction of cytoplasmic signals when sections were treated with RNase before RT reactions. To verify our protocol, transcript localization of the rbcS gene was examined in secondary stems of hybrid aspen (Populus tremula L. ×tremuloides Michx.) and compared to the chlorophyll autofluorescence signal. The in situ RT-PCR signals form the rbcS gene and chlorophyll autofluorescence co-localized in the same cell types. The signal was also confirmed by Northern blot analysis of isolated RNA from the cambium and developing xylem, thus confirming the validity of the protocol. Some difficulties of in situ transcript localization and the interpretation of the signal distribution in the secondary tissues are discussed.

@article{bourquin_xyloglucan_2002,
	title = {Xyloglucan {Endotransglycosylases} {Have} a {Function} during the {Formation} of {Secondary} {Cell} {Walls} of {Vascular} {Tissues}},
	volume = {14},
	issn = {1040-4651},
	url = {https://doi.org/10.1105/tpc.007773},
	doi = {10/cfv573},
	abstract = {Xyloglucan transglycosylases (XETs) have been implicated in many aspects of cell wall biosynthesis, but their function in vascular tissues, in general, and in the formation of secondary walls, in particular, is less well understood. Using an in situ XET activity assay in poplar stems, we have demonstrated XET activity in xylem and phloem fibers at the stage of secondary wall formation. Immunolocalization of fucosylated xylogucan with CCRC-M1 antibodies showed that levels of this species increased at the border between the primary and secondary wall layers at the time of secondary wall deposition. Furthermore, one of the most abundant XET isoforms in secondary vascular tissues (PttXET16A) was cloned and immunolocalized to fibers at the stage of secondary wall formation. Together, these data strongly suggest that XET has a previously unreported role in restructuring primary walls at the time when secondary wall layers are deposited, probably creating and reinforcing the connections between the primary and secondary wall layers. We also observed that xylogucan is incorporated at a high level in the inner layer of nacreous walls of mature sieve tube elements.},
	number = {12},
	urldate = {2021-10-19},
	journal = {The Plant Cell},
	author = {Bourquin, Veronica and Nishikubo, Nobuyuki and Abe, Hisashi and Brumer, Harry and Denman, Stuart and Eklund, Marlin and Christiernin, Maria and Teeri, Tunla T. and Sundberg, Björn and Mellerowicz, Ewa J.},
	month = dec,
	year = {2002},
	pages = {3073--3088},
}

Xyloglucan transglycosylases (XETs) have been implicated in many aspects of cell wall biosynthesis, but their function in vascular tissues, in general, and in the formation of secondary walls, in particular, is less well understood. Using an in situ XET activity assay in poplar stems, we have demonstrated XET activity in xylem and phloem fibers at the stage of secondary wall formation. Immunolocalization of fucosylated xylogucan with CCRC-M1 antibodies showed that levels of this species increased at the border between the primary and secondary wall layers at the time of secondary wall deposition. Furthermore, one of the most abundant XET isoforms in secondary vascular tissues (PttXET16A) was cloned and immunolocalized to fibers at the stage of secondary wall formation. Together, these data strongly suggest that XET has a previously unreported role in restructuring primary walls at the time when secondary wall layers are deposited, probably creating and reinforcing the connections between the primary and secondary wall layers. We also observed that xylogucan is incorporated at a high level in the inner layer of nacreous walls of mature sieve tube elements.

@article{mellerowicz_unravelling_2001,
	title = {Unravelling cell wall formation in the woody dicot stem},
	volume = {47},
	issn = {0167-4412},
	abstract = {Populus is presented as a model system for the study of wood formation (xylogenesis). The formation of wood (secondary xylem) is an ordered developmental process involving cell division, cell expansion, secondary wall deposition, lignification and programmed cell death. Because wood is formed in a variable environment and subject to developmental control, xylem cells are produced that differ in size, shape, cell wall structure, texture and composition. Hormones mediate some of the variability observed and control the process of xylogenesis. High-resolution analysis of auxin distribution across cambial region tissues, combined with the analysis of transgenic plants with modified auxin distribution, suggests that auxin provides positional information for the exit of cells from the meristem and probably also for the duration of cell expansion. Poplar sequencing projects have provided access to genes involved in cell wall formation. Genes involved in the biosynthesis of the carbohydrate skeleton of the cell wall are briefly reviewed. Most progress has been made in characterizing pectin methyl esterases that modify pectins in the cambial region. Specific expression patterns have also been found for expansins, xyloglucan endotransglycosylases and cellulose synthases, pointing to their role in wood cell wall formation and modification. Finally, by studying transgenic plants modified in various steps of the monolignol biosynthetic pathway and by localizing the expression of various enzymes, new insight into the lignin biosynthesis in planta has been gained.},
	language = {eng},
	number = {1-2},
	journal = {Plant Molecular Biology},
	author = {Mellerowicz, E. J. and Baucher, M. and Sundberg, B. and Boerjan, W.},
	month = sep,
	year = {2001},
	pmid = {11554475},
	keywords = {Cell Wall, Cellulose, Enzymes, Gene Expression Regulation, Developmental, Gene Expression Regulation, Plant, Lignin, Plant Stems, Trees, Wood},
	pages = {239--274},
}

Populus is presented as a model system for the study of wood formation (xylogenesis). The formation of wood (secondary xylem) is an ordered developmental process involving cell division, cell expansion, secondary wall deposition, lignification and programmed cell death. Because wood is formed in a variable environment and subject to developmental control, xylem cells are produced that differ in size, shape, cell wall structure, texture and composition. Hormones mediate some of the variability observed and control the process of xylogenesis. High-resolution analysis of auxin distribution across cambial region tissues, combined with the analysis of transgenic plants with modified auxin distribution, suggests that auxin provides positional information for the exit of cells from the meristem and probably also for the duration of cell expansion. Poplar sequencing projects have provided access to genes involved in cell wall formation. Genes involved in the biosynthesis of the carbohydrate skeleton of the cell wall are briefly reviewed. Most progress has been made in characterizing pectin methyl esterases that modify pectins in the cambial region. Specific expression patterns have also been found for expansins, xyloglucan endotransglycosylases and cellulose synthases, pointing to their role in wood cell wall formation and modification. Finally, by studying transgenic plants modified in various steps of the monolignol biosynthetic pathway and by localizing the expression of various enzymes, new insight into the lignin biosynthesis in planta has been gained.