The research in my group is focused on various aspects of the regulation of meristem identity and flowering time in the two model systems, Arabidopsis and poplar. We want to understand the level of functional conservation of genes regulating flowering time between the two systems and to identify new regulators of this transition. With this approach, we aim to gain more insight into the regulation of flowering in both annuals and perennials. In other projects, we are studying the regulation of plant development in response to light and the regulation of vascular cambium identity.

Nilsson Ove 1150
The transition to flowering is one of the most important events during the life of a plant.Although we know a lot about how this process is regulated in annual plants like Arabidopsis and rice, we still know very little about what controls flowering in perennial trees.

We have shown that the role of the Arabidopsis gene FT in regulating flowering time is functionally conserved in a plant with a completely different life strategy: the poplar tree. Surprisingly, we could also show that the FT gene in poplar trees controls another important aspect of perennial growth behaviour: the shortday induced growth cessation and bud set that occurs in the fall. We have shown that the activity of the CO/FT regulon is conserved in the aspen tree and that short days induce a down-regulation of the activity of this regulon, leading to growth cessation and bud set.These findings have led to a completely new way of looking at the function of FT. It seems that this gene has a much more general role in controlling photoperiodic regulation of plant growth and development than was previously anticipated, based on work in Arabidopsis.We have also shown that in sugarbeet only two amino acids are critical in determining if the two FT paralogs are acting as activators or repressors of flowering, and that the flowering repressor BvFT1 has a central role in the regulation of flowering in biennial sugar beet.We are now extending our comparative biology approach to study the similarities and differences in the regulation of flow- ering in Arabidopsis and the regulation of flowering and growth cessation in aspen (poplar) trees,This work will provide us with a better understanding of the genetic pathways responsible for photoperiodic regulation of plant growth and development. It will also allow us to design new ways to enhance the speed of tree breeding through accelerated flowering and to adapt the growing period of trees to new climate zones and to a changing climate.
ove_n_1 ove_n_2
Transgenic hybrid aspen tree forming inflorescences and flowers after 6 months instead of after 10-15 years The Nilsson group is also studying the genes controlling growth cessation, bud set and bud burst in trees

We have also cloned and characterized the BLADE-ON-PET- IOLE (BOP) genes, which have important roles in controlling the growth and development of lateral organs and appear to be important regulators of plant development in response to light. There is also an interes- ting interaction with the flower meristem identity-gene LEAFY (LFY) during flower initiation,in which BOP and LFY act together to initiate flower primordia and to suppress the outgrowth of flower-subtending leaves (bracts).

Recently,we identified a poplar ortholog of the shoot apical meristem identity gene WUSCHEL (WUS) ex- pressed in the vascular cambium and we have shown that this gene is important for vascular cambium activity and stem secondary growth.This is actually one of the genes that allow a tree to grow as a tree, i.e. to be the tallest plant in the forest.We are now characterizing several genes with a vascular cambium-specific expression pattern that could interact with this WUS-like gene in controlling the activity and identity of the vascular cambium. This knowledge will help to design methods to enhance wood production.

We are also extending our work on the regulation of flow- ering time and secondary growth into the conifer Norway spruce (Picea abies), where we recently led the effort to generate the first complete genome sequence.
sweden_greySvensk sammanfattning

Latest Publications

  1. Integrative Analysis of Three RNA Sequencing Methods Identifies Mutually Exclusive Exons of MADS-Box Isoforms During Early Bud Development in Picea abies
  2. LEAFY activity is post-transcriptionally regulated by BLADE ON PETIOLE2 and CULLIN3 in Arabidopsis
    New Phytol. 2018, 220(2):579-592
  3. A major locus controls local adaptation and adaptive life history variation in a perennial plant
    Genome Biol. 2018 Jun 4;19(1):72
  4. Transcriptome analysis of embryonic domains in Norway spruce reveals potential regulators of suspensor cell death
    PLoS One. 2018, 13(3):e0192945
  5. GIGANTEA-like genes control seasonal growth cessation in Populus
    New Phytol. 2018, 218 (4):1491-1503
  6. Transcriptional roadmap to seasonal variation in wood formation of Norway spruce
    Plant Physiol. 2018, 176(4):2851-2870
  7. BLADE-ON-PETIOLE proteins act in an E3 ubiquitin ligase complex to regulate PHYTOCHROME INTERACTING FACTOR 4 abundance
    Elife. 2017, e26759
  8. Functional metabolomics as a tool to analyze Mediator function and structure in plants
    PLoS One. 2017 Jun 22;12(6):e0179640
  9. AspWood: High-spatial-resolution transcriptome profiles reveal uncharacterized modularity of wood formation in Populus tremula
    Plant Cell. 2017, 29 (7):1585-1604
  10. WUSCHEL-RELATED HOMEOBOX4 (WOX4)-like genes regulate cambial cell division activity and secondary growth in Populus trees
    New Phytol. 2017, 215 (2):642-657
  11. Autumn senescence in aspen is not triggered by day length
    Physiol Plant. 2018, 162(1):123-134
  12. NorWood: a gene expression resource for evo-devo studies of conifer wood development
    New Phytol. 2017, 216(2):482-494
  13. Low temperatures are required to induce the development of fertile flowers in transgenic male and female early flowering poplar (Populus tremula L.)
    Tree Physiol. 2016, 36(5):667-677
  14. EU Regulations Impede Market Introduction of GM Forest Trees
    Trends Plant Sci. 2016, 21(4):283-285
  15. Molecular regulation of phenology in trees-because the seasons they are a-changin'
    Curr Opin Plant Biol. 2015, 29:73-79
  16. Electronic plants
    Sci Adv. 2015; 1(10):e1501136
  17. FT overexpression induces precocious flowering and normal reproductive development in Eucalyptus
    Plant Biotechnol J. 2016, 14 (2):808-819
  18. CLE peptide signaling in plants - the power of moving around
    Physiol Plant. 2015, 155(1):74-87
  19. Class I KNOX transcription factors promote differentiation of cambial derivatives into xylem fibers in the Arabidopsis hypocotyl
    Development 2014, 141(22):4311-4319
  20. Successful crossings with early flowering transgenic poplar: interspecific crossings, but not transgenesis, promoted aberrant phenotypes in offspring
    Plant Biotechnol J. 2014; 12(8):1066-1074
  21. Insights into Conifer Giga-Genomes
    Plant Physiol. 2014, 166(4):1724-32
  22. The Arabidopsis LRR-RLK, PXC1, is a regulator of secondary wall formation correlated with the TDIF-PXY/TDR-WOX4 signaling pathway
    BMC Plant Biol. 2013; 13: 94. Published online 2013 July 1
  23. The Norway spruce genome sequence and conifer genome evolution
    Nature 2013; 497(7451):579-584
  24. Klintenäs M, Pin PA, Benlloch R, Ingvarsson PK, Nilsson O
    Analysis of conifer FLOWERING LOCUS T/TERMINAL FLOWER1-like genes provides evidence for dramatic biochemical evolution in the angiosperm FT lineage
    New Phytol. 2012, 196(4):1260-1273
  25. Pin PA, Nilsson O
    The multifaceted roles of FT in plant development
    Plant Cell Environ. 2012 Jun 14 [Epub ahead of print]
  26. Pin PA, Zhang W, Vogt SH, Dally N, Büttner B, Schulze-Buxloh G, Jelly NS, Chia TY, Mutasa-Göttgens ES, Dohm JC, Himmelbauer H, Weisshaar B, Kraus J, Gielen JJ, Lommel M, Weyens G, Wahl B, Schechert A, Nilsson O, Jung C, Kraft T, Müller AE
    The Role of a Pseudo-Response Regulator Gene in Life Cycle Adaptation and Domestication of Beet
    Curr Biol. 2012, 22(12):1095-1101
  27. Plackett AR, Powers SJ, Fernandez-Garcia N, Urbanova T, Takebayashi Y, Seo M, Jikumaru Y, Benlloch R, Nilsson O, Ruiz-Rivero O, Phillips AL, Wilson ZA, Thomas SG, Hedden P
    Analysis of the developmental roles of the Arabidopsis gibberellin 20-oxidases demonstrates that GA20ox1, -2, and -3 are the dominant paralogs.
    Plant Cell. 2012; 24(3):941-60
  28. Elfving N, Davoine C, Benlloch R, Blomberg J, Brännström K, Müller D, Nilsson A, Ulfstedt M, Ronne H, Wingsle G, Nilsson O, Björklund S
    The Arabidopsis thaliana Med25 mediator subunit integrates environmental cues to control plant development
    Proceedings of the National Academy of Sciences of the United States of America: 2011 108:8245-8250
  29. Pin PA, Benlloch R, Bonnet D, Wremerth-Weich E, Kraft T, Gielen JJL, Nilsson O
    An antagonistic pair of FT homologs mediates the control of flowering time in sugar beet
    Science: 2010 330:1397-1400
  30. Nilsson O
    Plant Evolution: Measuring the length of the day
    Current Biology: 2009 19:R302-R303
  31. Rieu I, Eriksson S, Powers SJ, Gong F, Griffiths J, Woodley L, Benlloch R, Nilsson O, Thomas SG, Hedden P, Phillips AL
    Genetic analysis reveals that C-19-GA 2 oxidation is a major gibberellin inactivation pathway in Arabidopsis
    The Plant Cell: 2008 20(9):2420-2436
  32. Rieu I, Eriksson S, Powers SJ, Gong F, Griffiths J, Woodley L, Benlloch R, Nilsson O, Thomas SG, Hedden P, Phillips AL
    Genetic analysis reveals that C-19-GA 2 oxidation is a major gibberellin inactivation pathway in Arabidopsis
    The Plant Cell: 2008 20(9):2420-2436
  33. Rieu I, Ruiz-Rivero O, Fernandez-Garcia N, Griffiths J, Powers SJ, Gong F, Linhartova T, Eriksson S, Nilsson O, Thomas SG, Phillips A, Hedden P
    The gibberellin biosynthetic genes AtGA20ox1 and AtGA20ox2 act, partially redundantly, to promote growth and development throughout the Arabidopsis life cycle
    The Plant Journal: 2008 53:488-504
  34. Rieu I, Ruiz-Rivero O, Fernandez-Garcia N, Griffiths J, Powers SJ, Gong F, Linhartova T, Eriksson S, Nilsson O, Thomas SG, Phillips A, Hedden P
    The gibberellin biosynthetic genes AtGA20ox1 and AtGA20ox2 act, partially redundantly, to promote growth and development throughout the Arabidopsis life cycle
    The Plant Journal: 2008 53:488-504
  35. Bohlenius H, Huang T, Charbonnel-Campaa L, Brunner AM, Jansson S, Strauss SH, Nilsson O
    CO/FT regulatory module controls timing of flowering and seasonal growth cessation in trees
    Science: 2006 312:1040-1043
  36. Tuskan GA, DiFazio S, Jansson S, Bohlmann J, Grigoriev I, Hellsten U, Putnam N, Ralph S, Rombauts S, Salamov A, Schein J, Sterck L, Aerts A, Bhalerao RR, Bhalerao RP, Blaudez D, Boerjan W, Brun A, Brunner A, Busov V, Campbell M, Carlson J, Chalot M, Chapman J, Chen GL, Cooper D, Coutinho PM, Couturier J, Covert S, Cronk Q, Cunningham R, Davis J, Degroeve S, Dejardin A, Depamphilis C, Detter J, Dirks B, Dubchak I, Duplessis S, Ehlting J, Ellis B, Gendler K, Goodstein D, Gribskov M, Grimwood J, Groover A, Gunter L, Hamberger B, Heinze B, Helariutta Y, Henrissat B, Holligan D, Holt R, Huang W, Islam-Faridi N, Jones S, Jones-Rhoades M, Jorgensen R, Joshi C, Kangasjarvi J, Karlsson J, Kelleher C, Kirkpatrick R, Kirst M, Kohler A, Kalluri U, Larimer F, Leebens-Mack J, Leple JC, Locascio P, Lou Y, Lucas S, Martin F, Montanini B, Napoli C, Nelson DR, Nelson C, Nieminen K, Nilsson O, Pereda V, Peter G, Philippe R, Pilate G, Poliakov A, Razumovskaya J, Richardson P, Rinaldi C, Ritland K, Rouze P, Ryaboy D, Schmutz J, Schrader J, Segerman B, Shin H, Siddiqui A, Sterky F, Terry A, Tsai CJ, Uberbacher E, Unneberg P, Vahala J, Wall K, Wessler S, Yang G, Yin T, Douglas C, Marra M, Sandberg G, de Peer YV, Rokhsar D
    The genome of black cottonwood, Populus trichocarpa (Torr. & Gray)
    Science: 2006 313:1596-1604
  37. Norberg M, Holmlund M, Nilsson O
    The BLADE ON PETIOLE genes act redundantly to control the growth and development of lateral organs
    Development: 2005 132:2203-2213
  38. Andersson A, Keskitalo J, Sjodin A, Bhalerao R, Sterky F, Wissel K, Tandre K, Aspeborg H, Moyle R, Ohmiya Y, Bhalerao R, Brunner A, Gustafsson P, Karlsson J, Lundeberg J, Nilsson O, Sandberg G, Strauss S, Sundberg B, Uhlen M, Jansson S, Nilsson P
    A transcriptional timetable of autumn senescence
    Genome Biology: 2004 5:R24
  39. Brunner AM, Nilsson O
    Revisiting tree maturation and floral initiation in the poplar functional genomics era
    New Phytologist: 2004 164:43-51
  40. Sterky F, Bhalerao RR, Unneberg P, Segerman B, Nilsson P, Brunner AM, Campaa LC, Lindvall JJ, Tandre K, Strauss SH, Sundberg B, Gustafsson P, UhlEn M, Bhalerao RP, Nilsson O, Sandberg G, Karlsson J, Lundeberg J, Jansson S
    A Populus EST resource for plant functional genomics
    Proc Natl Acad Sci U S A: 2004 101:13951-13956
  41. Bhalerao R, Nilsson O, Sandberg G
    Out of the woods: forest biotechnology enters the genomic era
    Curr Opin Biotechnol: 2003 14:206-213
  42. Nilsson O, Lee I, Blázquez MA, Weigel D
    Flowering-time genes modulate the response to LEAFY activity
    Genetics: 1998 150:403-410
  43. Parcy F, Nilsson O, Busch MA, Lee I, Weigel D
    A genetic framework for floral patterning
    Nature: 1998 395:561-566
  44. Blazquez MA, Green R, Nilsson O, Sussman MR, Weigel D
    Gibberellins promote flowering of Arabidopsis by activating the LEAFY promoter
    Plant Cell: 1998 10:791-800
  45. Nilsson O, Wu E, Wolfe DS, Weigel D
    Genetic ablation of flowers in transgenic Arabidopsis
    Plant J: 1998 15:799-804
  46. Lee I, Wolfe DS, Nilsson O, Weigel D
    A LEAFY co-regulator encoded by UNUSUAL FLORAL ORGANS
    Curr Biol: 1997 7:95-104
  47. Nilsson O, Weigel D
    Modulating the timing of flowering
    Current Opinion in Biotechnology: 1997 8:195-199
  48. Nilsson O, Olsson O
    Getting to the root: The role of the Agrobacterium rhizogenes rol genes in the formation of hairy roots
    Physiologia Plantarum: 1997 100:463-473
  49. Nilsson O, Tuominen H, Sundberg B, Olsson O
    The Agrobacterium rhizogenes rolB and rolC promoters are expressed in pericycle cells competent to serve as root initials in transgenic hybrid aspen
    Physiologia Plantarum: 1997 100:456-462
  50. Nilsson O, Little CHA, Sandberg G, Olsson O
    Expression of two heterologous promoters, Agrobacterium rhizogenes rolC and cauliflower mosaic virus 35S, in the stem of transgenic hybrid aspen plants during the annual cycle of growth and dormancy
    Plant Molecular Biology: 1996 31:887-895
  51. Nilsson O, Moritz T, Sundberg B, Sandberg G, Olsson O
    Expression of the Agrobacterium rhizogenes rolC Gene in a Deciduous Forest Tree Alters Growth and Development and Leads to Stem Fasciation
    Plant Physiol: 1996 112:493-502
  52. Weigel D, Nilsson O
    A developmental switch sufficient for flower initiation in diverse plants
    Nature: 1995 377:495-500
  53. Imbault N, Moritz T, Nilsson O, Chen HJ, Bollmark M, Sandberg G
    Separation and Identification of Cytokinins Using Combined Capillary Liquid-Chromatography Mass-Spectrometry
    Biological Mass Spectrometry: 1993 22:201-210
  54. Nilsson O, Crozier A, Schmulling T, Sandberg G, Olsson O
    Indole- 3- Acetic- Acid Homeostasis in Transgenic Tobacco Plants Expressing the Agrobacterium- Rhizogenes Rolb Gene
    Plant Journal: 1993 3:681-689
  55. Nilsson O, Moritz T, Imbault N, Sandberg G, Olsson O
    Hormonal Characterization of Transgenic Tobacco Plants Expressing the Rolc Gene of Agrobacterium-Rhizogenes Tl-DNA
    Plant Physiology: 1993 102:363-371
  56. Olsson O, Nilsson O, Koncz C
    Novel monomeric luciferase enzymes as tools to study plant gene regulation in vivo
    J Biolumin Chemilumin: 1990 5:79-87