十年来申请人一直从事水稻种子大小与垩白调控的分子机理研究，以第一完成人分离克隆了正调控水稻种子大小和千粒重的QTL基因GS5，以及第一个稻米垩白主效QTL基因Chalk5。揭示了GS5调控种子大小的细胞学原因，鉴定了GS5 和Chalk5的功能性遗传变异，证明了Chalk5对稻米品质性状具有大的、普遍性影响，首次系统提出了Chalk5调控垩白形成的生化、分子和细胞学机理，丰富和发展了稻米品质和产量调控的分子机理。以第一作者在Nature genetics发表论文2篇、其它SCI刊物发表论文2篇。部分成果获2011年度“中国高等学校十大科技进展”奖和第十四届湖北省自然科学优秀学术论文（特等奖）。担任5种SCI期刊审稿人，在国内外学术会议上作报告8次。本项目拟以申请人克隆的GS5基因为对象，用分子、生化、遗传等多种策略鉴定GS5的互作蛋白及其调控种子大小的分子网络，丰富人们对其分子机理的认识。

I have been focusing on the molecular mechanisms of regulating both grain size and chalkiness in rice for ten years. We have successfully isolated the QTL gene positively regulating rice grain size and 1000-grain weight, GS5, and the first major QTL gene for rice grain chalkiness, Chalk5. We have revealed the cellular causes controlling grain size and chalkiness by GS5 and Chalk5, respectively, and identified the functional variations of both GS5 and Chalk5. We have confirmed that Chalk5 has large and general effects on multiple quality traits of rice grain. We have systematically uncovered the molecular, biochemical and cytologic mechanisms for the formation of grain chalkiness based on the results from Chalk5. These results have greatly enriched and developed the regulating mechanisms of grain quality and yield, and provided molecular evidences for the inconsistency and consistency between rice grain yield and quality caused by the three tightly linked genes, GS5, qSW5 and Chalk5. 4 first-author articles have been collected by SCI and 2 of them were published on Nature Genetics. A part of our results has gained many honors and awards, such as “Top Ten Progresses in Science and Technology of Universities in China (2011)” and “Outstanding Papers from Hubei Province in Nature Science (Fourteenth, 2012)”. I have served as a reviewer for four SCI journals and many other journals, and have been invited to give talks in three international and four domestic conferences. This project is based on the previous works of the GS5 gene, and will focus on identifying the interacting factors, up- and down- stream genes of the GS5 protein by many molecular, biochemical and genetic strategies, to uncover the molecular networks and mechanisms underlying rice seed size regulation.

本项目首先以申请人最近分离克隆到的正调控水稻种子大小和千粒重的功能基因GS5为出发点和研究对象，鉴定了GS5的互作蛋白和作用机制（Xu et al. JXB, 2015）：GS5可与细胞膜蛋白OsBAK1-7的胞外LRR结构域互作，OsBAK1-7的LRR结构域也可与OsMSBP1互作，这种互作会促进OsBAK1-7的内吞；当细胞表面存在大量的GS5蛋白时，GS5与OsBAK1-7的互作会竞争性抑制后者与OsMSBP1的互作，从而阻止OsBAK1-7的内吞，这种竞争性互作可以在一定程度上解释为什么GS5的表达水平与表型正相关。由于GS5对水稻粒宽的效应较小，不再深入研究，而选择效应大的、能解决植物G蛋白信号传导关键基础性科学问题的“水稻粒长主效基因GS3调控机理”作为本项目的主要研究内容，该工作已经取得阶段性进展（未发表数据）：以发展水稻体内的IP-MS技术为核心手段寻找已知水稻种子大小关键因子（GS3、DEP1、RGA1和RGB1）的互作蛋白，完成了4个典型G蛋白的34个样品的IP-MS分析，获得了G蛋白循环成员及其调控因子和下游效应子共45个，利用膜蛋白的酵母双杂交技术点对点初步验证了其中的22个因子；通过构建133个G蛋白循环相关基因的CRISPR突变体库，发现上述许多互作蛋白与种子大小调控相关，为进一步研究水稻G蛋白循环及其信号传导的生物学功能提供了丰富的遗传材料和坚实的工作基础。在本项目支持下根据现有进展进一步提出和凝练了本课题组现在及未来志力于“水稻种子大小与垩白调控”研究的关键科学问题（李一博，2016），为稻米品质的定量遗传改良提供理论基础和技术保障。