AGL16-SVP协同调控开花时间与干旱适应的机制研究

Timing of flowering is essential for plant reproductive success, and is regulated by both genetic and environmental factors. Flowering time is also very important for stress adaption. Flowering repressors AGL16 and SVP can form a hetero-protein-complex in regulation of flowering time, but its function in plants’ adaptation to environmental stress still needs investigation. Recently we found that both AGL16 and SVP can directly bind to the transcriptional regulatory region in an ABA receptor gene, PYL8. Since PYL8 positively regulates drought resistance in Arabidopsis thaliana, it may participate in coordinating the floral transition and drought adaptation mediated by AGL16 and SVP. In this proposal, we will identify the transcriptional regulatory region in PYL8 bound by AGL16 and SVP, and test its transcriptional effect. The potential gene-regulatory-networks related to flowering time regulated by PYL8 will be investigated via mRNA profiling. Finally we will test the genetic interaction between PYL8 and AGL16-SVP complex and their coordinated regulation on flowering and drought adaptation in both Col-0 and Col-FRI backgrounds. By integrating these results in the current gene-regulatory-networks of flowering time and ABA signaling pathways, this study should promote our in-depth understanding of the coordinated regulation of flowering time and drought adaptation in plants, thus might provide new target genes for breeding and provide theoretical guidance for agriculture.

开花是植物生殖成功的关键，受遗传和环境协同调控，而开花时间调节是植物适应逆境的重要机制。现已发现开花抑制转录因子AGL16和SVP可形成异源蛋白复合体调控开花时间，但其在植物逆境适应中的作用尚不清楚。前期研究发现AGL16和SVP可分别结合到ABA受体基因PYL8染色质转录调控区，而PYL8正调控拟南芥的抗旱性，故PYL8可能参与AGL16和SVP调控的开花与干旱适应过程。本项目拟通过DNA-蛋白互作研究方法验证AGL16、SVP对PYL8启动子的结合与调控效应；利用RNA-seq解析PYL8调控开花可能的基因网络；结合遗传互作和生理检测研究Col-0与Col-FRI背景下，AGL16、SVP突变和过表达时，PYL8协同调控拟南芥开花时间和干旱适应的作用机制。整合现有开花和ABA信号系统，为进一步丰富开花基因调控网络，解析开花与干旱适应之间的协同调控机制奠定基础，并为农业生产提供理论指导。

开花是高等植物生命周期中从营养生长向生殖生长转变的关键发育阶段,受遗传和环境因素的协同调控。植物激素脱落酸（ABA）影响植物的生长发育过程，并参与调控植物的一系列非生物胁迫响应。ABA受体PYR/PYLs是ABA信号的上游调控因子,通过ABA信号转导调控植物的生长发育及对逆境的响应，然而ABA受体是否参与开花时间调控尚不清楚。.本研究中我们发现ABA受体PYL8和PYL9组成型协同抑制拟南芥的开花时间。pyl8-1 pyl9双突变体在长日照下明显早花，而pyl8-1和pyl9单突变体没有明显的开花表型。PYL8启动子驱动的PYL8导入pyl8-1 pyl9双突变体中则可基本回补双突变体的早花表型。PYL8过量表达的转基因植株则显著较野生型晚花。表达分析发现pyl8-1 pyl9中开花整合因子FT和SOC1的转录水平明显上升；遗传分析表明FT和SOC1作用于PYL8和PYL9的下游。通过酵母双杂交和双分子荧光互补实验我们发现PYL8和PYL9与MADS-box家族的开花抑制因子AGL16在体外和体内均存在蛋白互作关系。长日照条件下pyl8-1 pyl9 agl16三突变体比pyl8-1 pyl9双突晚花，说明AGL16可能位于PYL8和PYL9的下游。染色质免疫共沉淀结合定量PCR实验表明PYL8和PYL9通过与AGL16互作促进了AGL16对SOC1启动子的结合；而PYL8和PYL9功能缺失后，AGL16对SOC1启动子的结合能力减弱，从而减轻了对SOC1表达的抑制作用，最终促进拟南芥开花。同时，AGL16也可以结合到PYL8启动子上，促进PYL8的瞬时表达。进一步遗传和生化实验表明PYL8和PYL9可与开花抑制因子SVP间接互作，但SVP的开花抑制效应是主效的。.综上所述，ABA受体PYL8和PYL9可以通过与AGL16等转录因子互作，直接调控SOC1基因的表达继而影响拟南芥的开花时间。本研究解析了ABA信号途径基因参与开花时间调控的新层面和分子机制，丰富了开花基因调控网络，也为进一步探索开花时间和环境适应协同调控的潜在分子机制提供了重要思路。