贮藏蛋白分选缺陷突变体是稻米蛋白品质改良研究的良好遗传材料。前期我们通过正向遗传学的研究鉴定了3个调控水稻贮藏蛋白后高尔基体分选的关键因子：GPA1/OsRab5a、GPA2/OsVPS9a和GPA3/OsKelch1，功能研究证实三者可形成一个功能蛋白复合体，协同调控贮藏蛋白的后高尔基体分选。近期，我们通过两个等位突变体分离了另外一个新的调控贮藏蛋白后高尔基体分选的关键因子GPA5，该蛋白含有一个可以特异结合磷酸肌醇-3-磷酸和磷酸肌醇-4-磷酸的结构域-PX。本项目拟进一步通过细胞、生化和分子生物学的技术手段，重点研究gpa5突变体胚乳发育的细胞学特性和GPA5基因的生物学功能，以期明确该基因调控水稻贮藏蛋白后高尔基体分选的分子作用机制，为全面解析水稻贮藏蛋白合成、分选和沉积的分子网络途径奠定基础，并为稻米蛋白品质改良提供遗传资源和理论支撑。

Mutants with defects in storage protein sorting are excellent genetic resources for studies on protein quality improvement in rice. We previously identified three essential regulators involved in post-Golgi trafficking of storage proteins in rice, including GPA1/OsRab5a, GPA2/OsVPS9a and GPA3/OsKelch1. Combined cytological, molecular and biochemical studies revealed that GPA3 forms a regulatory complex with OsRab5a via its interaction with OsVPS9a. Furthermore, genetic data demonstrated that GPA3 acts synergistically with GPA1 and GPA2 to regulate DV (Dense vesicle)-mediated post-Golgi traffic in rice. Recently, using two allelic post-Golgi sorting defect mutants, we identified another novel regulator with a PX domain required for lipid binding. Using cytological, biochemical and molecular biological technology and methods, this project will focus on studies on the developmental defects of endomembrane system in gpa5 endosperm cells and the molecular mechanism of GPA5 gene in regulating storage protein sorting. The completion of this project will expand our understanding of vesicle-mediated storage protein trafficking pathways and provide gene resourses and theoretical directions for protein quality improvement in rice.