GPA5 Encodes a Rab5a Effector Required for Post-Golgi Trafficking of Rice Storage Proteins

　　作者：Yulong Ren, Yihua Wang, Tian Pan, Yunlong Wang, Yongfei Wang, Lu Gan, Zhongyan Wei, Fan Wang, Mingming Wu, Ruonan Jing, Jiachang Wang, Gexing Wan, Xiuhao Bao, Binglei Zhang, Pengcheng Zhang, Yu Zhang, Yi Ji, Cailin Lei, Xin Zhang, Zhijun Cheng, Qibing Lin, Shanshan Zhu, Zhichao Zhao, Jie Wang, Chuanyin Wu, Lijuan Qiu, Haiyang Wang, Jianmin Wan*

　　影响因子：8.631

　　刊物名称： The Plant Cell

　　出版年份：January 2020

　　doi: 10.1105/tpc.19.00863

　　http://www.plantcell.org/content/early/2020/01/21/tpc.19.00863

　　Abstract

　　Dense vesicles (DVs) are vesicular carriers, unique to plants, that mediate post-Golgi trafficking of storage proteins to protein storage vacuoles (PSVs) in seeds. However, the molecular mechanisms regulating the directional targeting of DVs to PSVs remains elusive. Here, we show that the rice (Oryza sativa) glutelin precursor accumulation5 (gpa5) mutant is defective in directional targeting of DVs to PSVs, resulting in discharge of its cargo proteins into the extracellular space. Molecular cloning revealed that GPA5 encodes a plant-unique phox-homology domain-containing protein homologous to Arabidopsis thaliana ENDOSOMAL RAB EFFECTOR WITH PX-DOMAIN (EREX). We show that GPA5 is a membrane-associated protein capable of forming homodimers and that it is specifically localized to DVs in developing endosperm. Colocalization, biochemical, and genetic evidence demonstrate that GPA5 acts in concert with Rab5a and VPS9a to regulate DV-mediated post-Golgi trafficking to PSVs. Furthermore, we demonstrated that GPA5 physically interacts with a class C core vacuole/endosome tethering (CORVET) complex and a seed plant-specific VAMP727-containing R-soluble NSF attachment protein receptor (SNARE) complex. Collectively, our results suggest that GPA5 functions as a plant-specific effector of Rab5a required for mediating tethering and membrane fusion of DVs with PSVs in rice endosperm.