高級(jí)植物生理學(xué)課件第七章植物的生殖生理-在線瀏覽
2025-03-05 01:26本頁(yè)面
【正文】 utations in the clock genes 38 Temperature: Vernalization Vernalization: low temperature treatment can promote flowering in some plants. ? The vernalizationeffective temperature and duration of low temperature treatment may vary. ? Vernalization is perceived by the shoot apex. ? The vernalization state is grafting transmissible. Definition the acquisition or acceleration of the ability to flower by a chilling treatment ? Plants have evolved many systems to sense their environment and to modify their growth and development accordingly. One example is vernalization, the process by which flowering is promoted as plants sense exposure to the cold temperatures of winter. A requirement for vernalization is an adaptive trait that helps prevent flowering before winter and permits flowering in the favorable conditions of spring. In Arabidopsis and cereals, vernalization results in the suppression of genes that repress flowering. We describe recent progress in understanding the molecular basis of this suppression. In Arabidopsis, vernalization involves the recruitment of chromatinmodifying plexes to a clade of flowering repressors that are silenced epigeically via histone modifications. vernalization 41 ? Can be induced quickly ? Increases plant resistance to freezing stress ? Does not affect flowering time. Cold acclimation Venalization in cereals Machanism of Vernalization ? Vernalizationmediated changes in FLC chromatin. (a) Prior to cold exposure, FLC is actively expressed. The plexes that maintain this active chromatin conformation include the PAF plex, which methylates histone 3 tails at lysine 4 and 36 (H3K4triMe and H3K36triMe), a SWR1like plex, which deposits a histone 2A variant in the nucleosomes of FLC chromatin, and H2B ubiquitinases like HUB1 and HUB2 that ubiquitinate histone 2B tails (H2Bub1). Although FLC is in an active state, there are repressive plexes present such as Polyb Repression Complex 2 and some degree of lysine 27 methylation of histone 3 (H3K27triMe— a repressive modification) (b) During cold exposure, FLC repression is initiated. VIN3 is induced, VIN3 and VIL1/VRN5 associate with the Polyb plex, the density of repressive chromatin modifications such as lysine 27 methylation of histone 3 increases, and repressors such as LIKE HETEROCHROMATIN PROTEIN 1 (LHP1) assemble on FLC chromatin. (c) As vernalization proceeds, the density of repressive modifications, particularly H3K27triMe and lysine 9 methylation of histone 3 [H3K9triMe。 ? EXPRESSED IN: shoot apex, leaf whorl, embryo, flower, seed。 INVOLVED IN: flower development, maintenance of inflorescence meristem identity, response to gibberellin stimulus, gibberellic acid mediated signaling。. Also plays a role in the regulation of the time of flowering in the longday flowering pathway. May form plexes with phosphorylated ligands by inte
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