高級(jí)植物生理學(xué)課件第七章植物的生殖生理(編輯修改稿)
2025-02-12 01:26 本頁面
【文章內(nèi)容簡(jiǎn)介】 han a critical length to flower ?longday plant: required a light period longer than a critical length to flower ?Dayneutral plant: unaffected by photoperiod and flower when reaching a certain stage of maturity ?Vernalization: use of pretreatment with cold to induce flowering 32 The Arabidopsis biological clock The central oscillator: CCA1, LHY, and TOC1 (these are transcription factors) and other proteins 33 ? Present in plants, animals, fungi, and some photosynthetic bacteria ? An internal time measuring system (“clock”) that runs on its own with a periodicity of nearly 24 hours. It can be “reset” by external signals. The biological clock Temperature Biological clocks and circadian rhythms 36 The Arabidopsis biological clock ? CCA1 and LHY are expressed during the day and together repress expression of TOC1 during the day ? TOC1 is expressed at night and is required for activation of CCA1 and LHY1, beginning just before morning 37 ? Lack of the nyctinastic movement: diurnal rise and fall of leaves ? Altered flowering time in some mutants ? cca1: early flowering ? lhy: early flowering ? toc1: early flowering ? Some other clock mutants can be late flowering Mutations 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
教學(xué)課件相關(guān)推薦
鄂ICP備17016276號(hào)-1