剑叶叶绿素含量与叶片光合作用及产量潜力密切相关，是水稻育种中非常重要的生理性状。Ghd7是控制水稻抽穗期、株高和穗粒数的主效QTL，参与了时期转换、株型调控及胁迫反应等多个过程，本研究小组还发现它是控制剑叶叶绿素含量自然变异的主效位点。Ghd7编码转录因子且具有转录抑制活性，但其直接调控的靶基因及顺式作用元件一直未知。本项目申请人利用酵母单杂技术首次鉴定出4个在启动子区与Ghd7存在直接互作编码叶绿素合成过程中的酶及叶绿素a/b结合蛋白的靶基因。本项目拟进一步通过qRT-PCR、酵母单杂、凝胶阻滞及染色质免疫共沉淀等技术鉴定验证与转录因子GHD7直接互作的叶绿素代谢或光能捕获相关的靶基因，采取启动子截短及定点突变的方法确定关键顺式作用元件，阐明Ghd7与靶基因的表达模式及与叶绿素含量等表型的关系，并研究Ghd7与靶基因的遗传互作。本研究对于深入理解Ghd7的功能及指导育种实践具有重要意义。

Chlorophyll content in flag leaf is one of the most important physiological traits as it is closely related to leaf photosynthesis and crop yield potential. Grain number, plant height, and heading date7 (Ghd7) participates in multiple processes, including phase transition, architecture regulation, and stress response, and has been also demonstrated to be a major locus for natural variation of chlorophyll content at heading stage by our research group. Being a transcription factor, GHD7 has intrinsic transcriptional repression activity in vivo, however, the target genes and cis-acting elements remain unknown. Recently, by yeast one-hybrid assay, we have revealed that GHD7 can interact with the promoters of four genes encoding key enzymes of chlorophyll biosynthesis and light-harvesting chlorophyll a/b-binding proteins. In this research proposal, we plan to screen more candidate genes related to chlorophyll metabolism and light-harvesting, which were down-regulated by Ghd7 using qRT-PCR. The interaction of GHD7 protein with the promoters of candidate targets will be tested and verified through various approaches, such as yeast one-hybrid assay, electrophoretic mobility shift assay, and chromatin immunoprecipitation. The key cis-regulatory elements of GHD7 will be determined by designing a series of truncated and site-mutated promoters. The expression profile of Ghd7 and its target genes and how the trait of chlorophyll content is affected will be elucidated, and the genetic interaction mode between Ghd7 and its targets will be characterized. The research results will help understand in depth how Ghd7 functions and provide guidance for rice breeding.