一个新的水稻抽穗期调控基因SOF的鉴定与分子机理研究

Rice flowering time is one of the most important agronomic traits determining rice yield and regional adaptability. Identifying and characterizing novel flowering time genes is of great significance for the breeding high-yield rice cultivars. .In our previous study, a novel flowering regulating gene SOF (Suppressor of Flowering) was identified, SOF overexpression lines showed later flowering, whereas sof mutant flowered earlier, compared to wild type. SOF is a nucleus localized protein, and exhibits transcriptional activation activity and DNA binding activity. Interestingly, we found that expression of Hd2, a key flowering suppressor, is increased significantly in SOF-OE. Further experiments showed that SOF indeed binds to the promoter region of Hd2 gene. We thus speculate that SOF might delay flowering through promoting the Hd2 expression. .In this proposal, multiple discipline techniques (including genetics, biochemistry, and biology) will be combined to study whether and how SOF regulates Hd2, and dissects the functions site of SOF in flowering pathway. We believe this study will largely improve our understanding for the rice flowering regulation network, and provide novel target for rice molecular breeding.

抽穗期是决定水稻产量和种植区域的一个重要农艺性状。鉴定和解析抽穗期相关基因及其调控网络，对于培育水稻品种具有重要意义。本申请前期研究发现了一个新的水稻开花抑制基因SOF（Suppressor of Flowering），SOF过量表达材料晚花，sof突变体早花。SOF蛋白定位于细胞核，具有转录激活活性和DNA结合能力。进一步发现抽穗期抑制因子Hd2在SOF-OE中表达量显著升高，推测SOF通过提高Hd2的表达延迟水稻开花，初步利用体外实验证实SOF能结合Hd2启动子元件。为深入解析SOF调控开花的分子机制，本申请拟结合多种分子生物学手段，在植物体内研究SOF与Hd2的调控关系；利用双突变体研究SOF与Hd2在遗传学上的关系。本项目预期不仅鉴定新的水稻开花抑制因子SOF，还将揭示SOF调控水稻抽穗期的分子机理，项目研究成果将为完善水稻抽穗期关系网络奠定理论基础，为分子育种提供理论指导。

水稻抽穗期是水稻种植的区域和季节适应性的一个重要农艺性状，目前已经鉴定到很多个水稻抽穗期基因，但水稻抽穗期关系网络并不完善。本项目鉴定到一个水稻抽穗期负调控因子SOF，对其功能鉴定发现无论长日照还是短日照，过量表达SOF延迟水稻开花，sof突变体提早水稻开花。对其表达特性研究发现SOF具有转录激活活性和DNA结合能力。遗传学手段分析表明SOF发挥功能不依赖于Hd2、Hd4和Hd5，而是通过结合到Ehd1的启动子区域抑制其转录活性，进一步对ehd1 sof双突变体抽穗期调查发现sof的早花功能丧失，呈现出与ehd1类似的熟期。随后对其调控机理探究发现SOF与PRC2复合物的成员SDG711和FIE2存在相互作用，通过他们的互作能够招募PRC2复合物发挥对Ehd1的H3K27me3位点进行组蛋白甲基化修饰，进而延迟水稻开花。综上所述，本研究揭示了SOF通过招募PRC2复合物抑制Ehd1的转录发挥负调控水稻开花的分子机制，不仅为水稻开花途径的研究提供了一个新的视角，且为水稻育种工程提供了一个潜在的靶位点。