水稻高产分子设计育种是提高水稻产量的一条重要途径，而产量相关基因的定位、克隆和功能等遗传信息的获取则是高产分子设计育种的基础。申请人在前期工作中，从以籼稻8006为受体、武运粳8号为供体的高世代回交导入群体中筛选出一个每穗粒数比受体亲本显著减少的株系ZY08126，以此为材料构建衍生分离群体，鉴定出一个新的水稻每穗粒数主效QTL Gn2，现已将该基因精细定位在83kb距离内。本项目拟在已有研究基础上进一步精细定位Gn2，根据生物信息学预测、cDNA测序和相关表达分析确定候选基因；通过构建互补、过表达和RNAi载体验证候选基因的功能；利用基因功能分析软件，明确基因结构和蛋白质结构；利用Real-time PCR和GUS染色等手段分析基因表达的时空特性；通过GFP-Gn2融合蛋白进行亚细胞定位；通过组织切片解析Gn2调控的形态学和生理学基础。本研究为揭示水稻每穗粒数调控的分子机制提供重要信息。

Rice (Oryza sativa L.) is one of the most important staple food crops in the world and is consumed by more than 50% of the world′s population. Increasing rice grain yield will be required in order to feed the increasing global population in the next decades. High-yield molecular design breeding is considered as a vital approach to enhance rice production. Grain yield in rice is determined by three main components: panicle number per plant, grain number per panicle and grain weight. So the genetic information of these genes is the foundation for high-yield molecular design breeding. In our previous study, we constructed a backcrossing introgression line population using an indica cultivar, 8006, as the recurrent parent and a japonica cultivar, Wuyunjing 8, as the donor parent. One line of the population, ZY08126, exhibited significant decreased grain number per panicle compared with the recurrent parent. To uncover the genetic basis of this variation, a segregated population was developed by selfing the F1 plants of ZY08126 and 8006. A major QTL named Gn2 regulating grain number per panicle was detected out. QTL and genetic analysis indicated that Gn2 contributed 32.3% of phenotypic variation and acted as a single Mendelian factor in this population. Gn2 has been narrowed into a 83-Kb region in chromosome 2. In this project, we are going to carry out the fine mapping of Gn2 and a complementary test will be used to confirm the candidate gene. NILs, RNAi and overexpressed transgenic lines will be developed and employed to reveal the biological function of Gn2. In addition, the allelic variation of Gn2 in various rice varieties will be analyzed by DNA sequencing. These results will provide useful information for rice molecular improvement.