水稻种子大小和千粒重的两个新QTL基因GL1和GW5.1的克隆与功能研究

水稻种子大小（粒形）是一个重要的稳产、外观和加工品质、驯化、育种及形状发生与发育的靶标性状。前期工作中我们从遗传多样性很广的世界水稻微核心种质中发现了两个新的、效应很大的控制水稻种子大小、千粒重和产量的数量性状位点GL1和GW5.1，但其分子功能和调控机理仍不清楚。本项目先用图位克隆、比较测序、比较表达、转基因等分析验证了两个基因的生物学功能，再拟用细胞学和酶活比较分析确定其基本的细胞和生化机制；用酵母双杂交、免疫沉淀质谱联用、已知粒形关键基因等方法鉴定其互作蛋白，再用免疫共沉淀、双分子荧光互补、转基因等技术对互作蛋白进行生化和遗传上的双重验证，来剖析其调控种子大小的分子机理。另外，用水稻微核心种质对两个基因进行遗传多样性和嵌合载体转基因分析，分别确定其最优良等位基因和功能性变异。本研究的完成，不仅将丰富种子大小自然变异的分子基础，还将为水稻分子育种提供新基因，在理论和实践上具有重要意义。

Rice grain size/shape is an important stable yield and quality trait, a target trait of domestication, breeding and morphogenesis. In the previous study, we identified two novel and major QTLs, GL1 and GW5.1, for rice grain size, weight and yield using a rice mini-core collection with a diverse diversity, but the genes underlying these QTLs and their regulating functions are unknown. In this project based on the previous work, we almost confirmed the two functional genes by map-based cloning methods, comparative sequencing and expression analyses coupled with genetic transformation analyses. We will then reveal the basic cellular and biochemical functions of GL1 and GW5.1 by discovering cellular causes and their differences of enzyme activities. Moreover, we will first identify the putative interacting proteins of GL1 and GW5.1 using analyses of Y2H, IP-MS and well-known grain-size genes, and then confirm these proteins by both biochemical and genetic analyses, including Co-IP, Split-LUC and genetic transformation analyses, respectively, to uncover the molecular mechanisms of GL1 and GW5.1 for regulating rice grain size. In addition, we will perform the genetic diversity and genetic transformation analyses using chimeric vectors to identify the favorable alleles and functional variations of GL1 and GW5.1 for rice genetic improvement using rice mini-core collections. The identification and functional analyses of the GL1 and GW5.1 genes will not only make great contributions to comprehensively understanding the molecular basis of grain-size variations, but also provide two novel genes for molecular breeding, making very good sense in both theory and practice.