分枝(分蘖)数目和开花时间分别是作物株型和生态区适应性的关键决定因素，并最终影响作物产量。密植栽培条件会诱发植物的避荫反应，导致分枝数降低和开花提早，但其遗传和分子调控机理尚不清楚。前期研究发现拟南芥光信号转导因子FHY3和FAR1参与植株分枝数和开花时间的调控，并可与多个SPL转录因子直接互作，后者可与调控分枝关键基因BRC1和开花关键基因FUL的启动子直接结合。本项目将从三个方面验证FHY3/FAR1通过与SPL蛋白互作协同调控BRC1和FUL的表达，从而调控植株分枝数和开花时间的假说。1）验证FHY3/FAR1与SPL蛋白体内和体外互作；2）解析FHY3/FAR1与SPL协同调控BRC1和FUL表达的分子机制；3）建立FHY3/FAR1与SPL互作响应遮荫条件调控分枝数和开花时间的遗传网络。研究成果将加深对我们对植物株型和开花时间调控机理的的理解，并为耐密植作物新品种培育提供指导。

Branch (tiller) number and flowering time are key determining factors of plant architecture and regional adaptation, respectively, and they greatly influence the final yield of crops. Increasing the planting density is a key measurement of increasing crop yield per unit land area. However, high density planting causes a reduction in the red:far-red ratio, thus inducing shade avoidance syndrome, including reduction of branch number and early flowering. The molecular genetic mechanisms governing these processes remain poorly understood. We found that in Arabidopsis, FHY3 and FAR1, a pair of homologous genes required for phytochromeA signaling, are involved in shade regulation of branching and flowering. In addition, FHY3 and FAR1 physically interact with multiple members of the SPL gene family. Moreover, we found that multiple SPL proteins can directly bind to the promoters of BRC1 and FUL, which are known key regulatory factor of branching and flowering respectively. Thus, we propose that FHY3/FAR1 and SPL proteins coordinately regulate the expression of BRC1 and FUL, which in turn regulate branching and flowering. In this project, we will verify this working hypothesis. Specifically, we will: 1) Verify the in vivo and in vitro interaction between FHY3/FAR1 and SPLs; 2) Elucidate the molecular mechanisms of FHY3/FAR1-SPL interaction in regulating the expression of BRC1 and FUL; 3) Establish the genetic regulatory network of FHY3/FAR1-SPL interaction in regulating branching and flowering in response to high density or shade conditions. The expected results will greatly enhance our understanding of the molecular mechanisms regulating plant architecture and flowering time in plants, but also help to guide breeding of high density-tolerant crop cultivars.