拟南芥TrxG因子在成花素基因FT表观遗传调控中的分子机理研究

Light, as one of the most important environmental signals, affects plant growth and development. Many plant species, especially those located at high latitudes, monitor changes in seasonal cues, such as day length and photoperiod, and regulate the adaptive flowering response through the photoperiod pathway. Hence, photoperiodism is crucial for crop introduction. Florigen FT acts as an integrator in response to changes in day length and is specifically activated at dusk by the photoperiod pathway output CO. Analysis of flowering placed the CO-FT module at the core of photoperiod pathway. Recent studies demonstrated that PcG proteins represses FT expression before dusk and at night, to prevent photoperiod-independent early flowering. Up to date, little is known about how CO and PcG factors which are involved in different processes of FT regulation interact. Based on our previous results, we will study the roles of transcriptional co-activators TrxG in FT chromatin state switch. Moreover, we propose to elucidate the synergistic relationship between TrxG factors and CO, as well as the counterbalance between TrxG proteins and PcG proteins in proper FT expression fitting to the photoperoid. Our study will reveal the role of TrxG involved in integrative mechanism between transcriptional activation and epigenetic silencing of FT, and will provide new insight into regulatory mechanism by which the seasonal changes regulate plant growth and development.

光是影响植物生长发育最重要的外源环境信号因子，植物通过对季节信号——日照长度的应答与适应，决定其个体生长与群体分布，光周期特性是农作物引种需要考虑的关键因素之一。成花素FT是响应日照长度的关键整合因子，光周期途径输出因子CO在黄昏特异激活FT表达，CO-FT调控单元是光周期途径的核心调控模式；PcG因子在黄昏之前及晚上抑制FT的表达，使植物避免非光周期依赖的提早开花。然而，CO和PcG参与的相反的FT调控过程如何联系？其分子机制迄今未知。本项目拟研究转录共激活因子TrxG在光周期介导FT的染色质状态转变中的作用，将阐明TrxG因子通过协同转录因子CO促进FT表达，同时拮抗PcG因子对FT的抑制作用，使得FT呈现特异的光周期表达模式，确保植物适时开花。研究结果将揭示TrxG因子在FT的转录激活和表观抑制中的整合机制，对阐明季节变化（光周期）调控植物成花转变这一科学问题具有理论意义。

光照是影响植物生长发育最重要的外源环境信号因子，植物对光信号的应答与适应，塑造着植物从自养生物向异养生物的神奇转变，决定着植物个体生长与群体分布，光周期特性是进行农作物引种时需要考虑的关键因素。.本项目系统研究了成花素基因FT及其它光响应基因的表观遗传调控机制，发现FT的染色质响应光周期，黄昏时“开放”，表达激活；傍晚时“关闭”，表达抑制。染色质重塑因子PKL通过改变FT染色质状态，有利于转录调控因子CO接近FT位点，调控其转录 (Plant, Cell & Environment, 2019)。VAL1识别并结合FT内含子顺式沉默元件，从而将PcG蛋白LHP1和MSI1至FT染色质，从而介导PcG因子对FT的表观抑制 (Plant Physiology, 2019)。TrxG蛋白ATX1和TrxG类蛋白PKL拮抗PcG介导的对FT的转录抑制，两类蛋白维持了FT的特异且适当表达，从而调控光周期开花 (Plant Physiology, 2019)。SNL-HDA19去乙酰化酶复合物和转录因子HY5相互作用，拮抗调控关键光响应基因，塑造植物对不断变化光环境的适应性 (New Phytologist, 2021)。受邀撰写综述文章，系统总结和阐述了光信号（包括光周期）转录调控的研究进展 (New Phytologist, 2020)。.综上，我们鉴定到了一系列表观调控因子，它们在成花素基因FT和其它光响应基因的正确表达中发挥关键作用，这些研究揭示了转录调控在植物响应光环境的重要作用。