title: OsRab5a regulates endomembrane organization and storage protein trafficking in rice endosperm cells.
abstract: Rice glutelins are synthesized at the endoplasmic reticulum (ER) as precursors (pro-glutelins), and are transported to protein storage vacuoles, where they are processed into mature proteins. The molecular basis of this process is largely unknown. Here, we report the isolation of a rice mutant, gpa1, that accumulates 57 kDa pro-glutelins in seeds and whose endosperm has a floury appearance. Transmission electron microscopy analysis showed that the gpa1 endosperm cells have an enlarged ER lumen and a smaller protein body II (PBII), and accumulated three types of newly generated subcellular structures. Moreover, a proportion of glutelins in the gpa1 endosperm cells were not delivered to PBII, and instead were mis-targeted to two of the newly generated structures or secreted. The gene corresponding to the gpa1 mutation was found to be OsRab5a, which encodes a small GTPase. In Arabidopsis protoplasts, OsRab5a protein was found to co-localize predominantly with AtVSR2, a molecular marker for the pre-vacuolar compartments (PVC). We conclude that OsRab5a plays an essential role in trafficking of storage protein to PBII, possibly as part of its function in organizing the endomembrane system in developing endosperm cells of rice.
authors.affiliation: State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Yihua
authors.initials: Y
authors.lastname: Wang
authors.forename: Yulong
authors.initials: Y
authors.lastname: Ren
authors.forename: Xi
authors.initials: X
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
authors.forename: Liangming
authors.initials: L
authors.lastname: Chen
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Han
authors.forename: Mingna
authors.initials: M
authors.lastname: Jin
authors.forename: Shijia
authors.initials: S
authors.lastname: Liu
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Jia
authors.initials: J
authors.lastname: Lv
authors.forename: Kunneng
authors.initials: K
authors.lastname: Zhou
authors.forename: Ning
authors.initials: N
authors.lastname: Su
authors.forename: Yiqun
authors.initials: Y
authors.lastname: Bao
authors.forename: Jianmin
authors.initials: J
authors.lastname: Wan
mesh_terms: D002874:Chromosome Mapping; D056625:Endosperm / Q000378:metabolism* / Q000648:ultrastructure; D005816:Genetic Complementation Test; D005983:Glutens / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D018749:RNA, Plant / Q000235:genetics; D055314:Seed Storage Proteins / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant; D055314:Seed Storage Proteins; D005983:Glutens; D020696:rab5 GTP-Binding Proteins