Seminar - Claudio Stasolla: In vitro plant embryogenesis: improving embryo yield

UPSC Seminar

Sepaker:
Claudio Stasolla
Dept. Plant Science, University of Manitoba, Winnipeg, Canada

Title:
In vitro plant embryogenesis: improving embryo yield

Place: KB3A9, Lilla hörsalen

Host: Ulrika Egertsdotter

Plant embryogenesis is an essential phase of the plant life cycle and formation of embryos can be stimulated in vitro through the careful selection of media components and environmental conditions. Work in my lab has recently been focussed on the function of plant hemoglobins (Hbs) during somatic embryogenesis in dicots and monocots.   First described in animals, Hbs have now been identified in a variety of organisms including plants where their major function is to scavenge cellular nitric oxide (NO). Suppression of the Arabidopsis class 2 Hb (Hb2) enhances the formation of somatic embryos through the NO-mediated suppression of the transcription factor MYC2. Repression of MYC2 increases IAA accumulation at the sites of embryogenic tissue formation, and favors the formation of Arabidopsis somatic embryos.   In maize the two Hbs: ZmHb1 and ZmHb2 regulate the cell survival/death decision that influences somatic embryogenesis through their cell-specific localization patterns. Suppression of either of the two ZmHbs is sufficient to induce PCD through a pathway initiated by elevated nitric oxide (NO) and zinc (Zn²⁺⁾ levels, and mediated by production of reactive oxygen species (ROS). The effect of the death program on the fate of the developing embryos is dependent upon the localization patterns of the two ZmHbs. During somatic embryogenesis, ZmHb2 transcripts are restricted to a few cells anchoring the embryos to the subtending embryogenic tissue, while ZmHb1 transcripts extend to several embryonic domains. Suppression of ZmHb2 induces PCD in the anchoring cells allowing the embryos to develop further, while suppression of ZmHb1 results in massive PCD leading to abortion. It is concluded that regulation of the expression of these ZmHbs has the capability to determine the developmental fate of the embryogenic tissue during somatic embryogenesis through their effect on PCD. These studies place Hbs as central regulators of in vitro embryogenesis