GW4调控水稻粒形的分子机制与育种利用研究

水稻粒形不但影响产量，也与稻米品质密切相关。因此，改良粒形是实现水稻高产优质育种的一条有效途径。申请人在以粳稻日本晴为受体、籼稻9311为供体的染色体片段代换系中鉴定到一个籽粒显著变宽的代换系N31。利用图位克隆等方法克隆到一个控制水稻粒形的新基因GW4，其突变会增加粒宽而过量表达籽粒细长。植物激素BR含量及敏感性分析等表明GW4是BR的负调控因子。本项目拟在此基础上，通过籽粒发育动态分析、细胞学观察等揭示GW4的表达和生物学功能，并进一步从转录组、蛋白组、激素调控、蛋白互作和遗传互作等角度深入分析其遗传效应及调控路径，探明GW4调控粒形的分子机制。同时，结合GW4目标区段重测序开展单倍型分析，挖掘其优异等位变异，并利用基因编辑方法定向改良GW4，分析其育种利用潜力。本项目的开展不仅可为水稻的粒形改良提供优异基因资源，还可为粒形调控分子网络及水稻BR调控机制的完善提供重要参考。

Rice grain size affects not only rice yield but also rice quality. It is an effective way to breed rice cultivars with high yield and good quality by selecting rice with favorable grain size. In our previous work, a rice line N31 with wider grain size was identified from the chromosome segment substitution lines derived from a cross between a japonica cultivar Nipponbare (receptor) and an indica cultivar 9311 (donor). We have successfully cloned a novel gene GW4 controlling grain size by using map-based cloning method. GW4 mutation could increase the width of rice grain while its overexpression could make the grain slender. The results of BR content and BR sensitivity analysis indicated that GW4 is a negative regulator of BR.. In this project, we are going to reveal the expression pattern and biological function of GW4 by dynamic analysis and microscopy observation of the developing seeds. Further experiments including RNA-sequencing, proteomics, phytohormone regulation, protein-protein interaction assays, and genetic interaction test will be performed to dissect the genetic effect and regulation mode of GW4, thus disclosing the molecular mechanism of GW4 in regulating grain size. Also, haplotype analysis will be carried out by resequencing the GW4 region of different rice varieties. Elite GW4 alleles will be identified and characterized. In addition, GW4 gene will be optimized by gene editing method and its potential application in rice breeding will also be evaluated. We believe that the results obtained from this project will not only provide elite gene resource for optimizing rice grain size, but also be helpful in improving grain size modulation molecular network and enhancing BR regulation modes in rice.