水稻籽粒灌浆调控基因GIF3的鉴定与功能研究

籽粒灌浆对稻米产量和品质的形成都极为重要，但水稻籽粒灌浆的分子调控网络仍不清晰，新的调控因子有待进一步挖掘与利用。申请人前期通过CRISPR-Cas9敲除技术对水稻着丝粒附近的基因进行敲除，并筛选灌浆缺陷突变体。从中筛选到3个灌浆速率明显下降的突变体，鉴定为同一基因Os09g0132600的等位敲除突变体，将该基因命名为GIF3。基因结构和亚细胞定位分析表明GIF3编码一个线粒体定位的RNA编辑因子。基于此，本项目将进行转基因互补验证GIF3的功能；并通过线粒体编辑位点分析和线粒体复合体活性分析来解析GIF3调控籽粒灌浆的分子机制；进一步通过GIF3互作蛋白验证和构建单、双突材料，研究互作蛋白GIP1在GIF3介导的调控籽粒灌浆途径中的作用，揭示GIF3调控水稻籽粒灌浆的分子调控网络途径。本项目研究结果将为水稻灌浆的分子机制提供新的认识，为高产和优质稻米品种的培育提供理论依据和基因资源。

Grain-filling rate plays a vital role in the regulation of rice grain yield and grain quality. However, the molecular regulatory network of rice grain-filling is still unclear, and new regulatory factors still need to be studied and utilized. In our previously work, many genes near the rice centromere were knocked out by using CRISPR-Cas9 system, and mutants with grain-filling defects were screened out. Three mutants with a significantly decreased grain-filling rate were identified, and sequencing analysis showed that they were all allelic mutants of the gene Os09g0132600, which named GIF3(GRAIN INCOMPLETE FILLING 3). Gene structure analysis and subcellular localization analysis showed that GIF3 encodes a mitochondrion-targeted RNA editing factor. Based on these previous studies, this project will perform transgene complementation to verify the function of GIF3. Subsequently, mitochondrial RNA editing efficiency analysis and mitochondrial complex activity analysis will be carried out to reveal the molecular regulation pathway of GIF3. Further, we will study the role of GIP1 (GIF3 interacting protein 1) in the grain-filling pathway that mediated by GIF3, and finally reveal the GIF3 molecular regulatory network in grain-filling. Our study of GIF3 will provided new insights to the molecular mechanism of rice grain-filling, and provide theoretical knowledge and gene resource for the breeding of high grain yield and quality rice cultivate.