水稻粒型与产量、品质密切相关。控制粒型基因的克隆、功能分析和分子调控机理的研究是水稻分子育种的基础。申请者在前期研究中克隆了水稻控制细长粒型的一个关键 QTL SLG7 (Slender Grain on chromosome 7)，可以显著提高籽粒长宽比并改良稻米的外观品质，但其分子机制尚不清楚。为了探明了其分子机理，利用酵母双杂技术筛选到了一个与其互作的蛋白SIP1(SLG7 Interacting Protein 1)，并利用pull-down技术进行了验证。本项目拟在此基础上，利用双分子荧光互补和免疫共沉淀等方法进一步验证SLG7和SIP1的互作；对SIP1基因进行CRISPR/Cas9敲除、基因过表达和RNA干扰，系统地构建一系列转基因株系，进行表型、形态解剖、生理生化和转录组学分析，解析SIP1的生物学功能及信号传导途径，揭示SIP1和SLG7互作调控水稻粒型的分子机制。

Rice grain yield and quality largely depend on grain size. Identification, functional analysis and genetic mechanism of the genes responsible for grain size provides foundation of molecular breeding. Previously, we identified a novel QTL, SLG7 (Slender Grain on chromosome 7), that is responsible for grain shape, using backcross introgression lines derived from 9311 and Azucena. The SLG7 allele from Azucena produces longer and thinner grains, although it has no influence on grain weight and yield production. However, the molecular mechanism of SLG7 remains unknown. We used yeast two-hybrid system to screen the interacting protein with SLG7. The interaction of SLG7 with SIP1 (SLG7 Interacting Protein 1) was confirmed by yeast two-hybrid and pull down. In this project, the interaction of SLG7 with SIP1 will also be confirmed by Bimolecular Fluorescence Complementation and Co-Immunoprecipitation assays. The biological function of SIP1 will be validated through RNA interference, overexpression and CRISPR/Cas9 mutant. Multiple biochemical, physiological and transcriptomics strategies will be employed to uncover the roles of SIP1. After the completion of the project, the molecular mechanism of SIP1-SLG7 interaction for rice grain size regulation will be clearly elucidated.