光周期途径与PcG复合体协同调控FT转录的分子机制研究

As one of the most important environmental factors for plant growth, light not only provides energy for photosynthesis, but also acts as an important signal to regulate the flowering initiation. It has been reported that the blue light photoreceptor Cryptochromes (CRYs) can absorb the light signal, and then transmit the signal to transcription factors CO and CIB1. After light activation, CO and CIB1 promote the transcription of florigen gene FT. However, the molecular mechanism of CO and CIB1 promoted FT transcription is still unclear. Epigenetic modification also plays an important role in the regulation of flowering time and the transcription of FT in plants, but the upstream signals of epigenetic modification need to be further studied. Our previous studies have found that the mutation of PcG (POLYCOMB GROUP) complex proteins leads to an increase in FT transcription independent of photoperiod. Therefore, on the basis of previous studies, this project will further explore the crosstalk between photoperiod pathway and PcG complex in flowering time regulation by using bioinformatics, genetics, biochemistry and molecular biology methods. It is of great scientific significance to study how plants transmit light signals to the PcG complex to induce the changes of FT chromatin modification, so as to uncover the mechanism of temporal and spatial specific regulation of FT transcription.

作为植物生长不可或缺的环境因素之一，光不仅为植物光合作用提供能量，而且还作为重要的环境信号调控植物的开花启始。已有研究表明蓝光受体隐花素CRYs能够接收蓝光信号，将蓝光信号传递给转录因子CO和CIB1，通过在转录水平正调控成花素基因FT的表达促进植物开花。但是CO和CIB1促进FT转录水平升高的具体分子机制尚不清楚。表观遗传修饰在植物的开花时间调控以及FT的转录水平调控上扮演重要角色，但是引起表观遗传修饰改变的上游信号仍有待进一步研究。我们前期研究发现表观遗传修饰因子PcG蛋白复合体成员的突变，会引起FT转录不依赖光周期升高。本项目计划在前期研究基础上，采用生物信息学、遗传学、生物化学以及分子生物学方法进一步探究光周期调控开花的重要元件与PcG复合体成员在FT转录调控中的相互关系。研究植物如何将光信号传递给PcG复合体引起FT染色质表观修饰变化，从而实现时空特异的FT转录调节。

作为植物生长不可或缺的环境因素之一，光不仅为植物提供光合作用的能量，而且还作为重要的环境信号调控植物的开花启始。已有研究表明蓝光受体隐花素CRYs能够接收光信号，将光信号传递给转录因子CO和CIB1,通过在转录水平上正调控成花素基因FT的表达促进植物开花。但是研究发现黑暗下CO和CIB1却不能激活FT转录。因此CO和CIB促进FT转录水平升高的具体分子机制有待进一步研究。本项目对蓝光调控开花和FT转录的本质进行研究发现，表观遗传修饰因子PcG（POLYCOMB GROUP）复合体蛋白成员LHP1，能够与CRY2直接相互作用。相对于黑暗条件，蓝光条件下，FT染色质水平上H3K27me3的表观修饰量显著降低。LHP1对FT染色质的结合在cry2突变体中显著增多。遗传学分析发现lhp1上位于光周期途径的重要因子cry2和co，但ft上位于lhp2。我们的实验结果证明光信号通过光受体CRY2，直接影响PcG复合体在FT染色质上的结合，从而影响H3K27me3表观修饰的变化，实现时空特异的调节FT转录。