水稻抽穗期作为重要的农艺性状与产量有着密切的联系。研究表明光敏色素B（phyB）抑制开花素基因Hd3a而延迟水稻的抽穗期，而分子机理并不清楚。光敏色素相互作用因子（PIFs）在光信号传导网络中起着核心作用。在水稻基因组中有6个与拟南芥高度同源的PIFs，分别命名为OsPIL11~OsPIL16。我们的研究结果表明，在长日照条件下过表达OsPIL15下调Hd3a的表达，延迟水稻抽穗，而且这种延迟作用需要功能性的phyB与OsPIL15相互作用。因此我们推测phyB可能通过OsPIL15调控水稻的抽穗期。在本项目中我们拟通过分析分子生物学、遗传学等手段分析OsPIL15基因突变体抽穗期表型、鉴定OsPIL15调控的靶基因及OsPIL15在phyB调控抽穗期途径上的位置，从而解析OsPIL15基因依赖于phyB调控水稻抽穗期的分子机制，为水稻抽穗期的分子改良提供新的思路。

Heading date, one of the most important agronomic traits, has the close relationship with rice yield. Previous studies show that phytochrome B (phyB) delayed rice heading date by down-regulating florigen Hd3a, but the molecular mechanism is not clear..Phytochrome-interacting factors (PIFs) play pivotal roles in the signal transduction network triggered by light. Six PIFs, which are highly homologous with those in Arabidopsis, are identified based on gene annotation in rice genome, and named OsPIL11~OsPIL16 respectively. Our previous studies showed that OsPIL15-overexpressed transgenic rice lines delayed heading date under long-day conditions and down-regulated the expression of Hd3a, and However, role of OsPIL15 in delaying heading date requires the interaction between OsPIL15 with functional phyB. Thus, we speculated that phyB delayed heading date through OsPIL15. In this project, we will compare the heading date of OsPIL15 transgenic lines with gain- and loss-of-function, and identify target genes of OsPIL15 using chromatin immunoprecipitation assays. Moreover, we will determine the role of OsPIL15 in the pathway of phyB-regulated rice heading date by means of genetic approaches, thus explaining the mechanism how OsPIL15 is involved in heading date mediated by phyB. The results from this study will provide the new strategy for rice molecular breeding with appropriate heading date.