title: The vacuolar processing enzyme OsVPE1 is required for efficient glutelin processing in rice.
abstract: Rice (Oryza sativa L.) accumulates prolamines and glutelins as its major storage proteins. Glutelins are synthesized on rough endoplasmic reticulum as 57-kDa precursors; they are then sorted into protein storage vacuoles where they are processed into acidic and basic subunits. We report a novel rice glutelin mutant, W379, which accumulates higher levels of the 57-kDa glutelin precursor. Genetic analysis revealed that the W379 phenotype is controlled by a single recessive nuclear gene. Using a map-based cloning strategy, we identified this gene, OsVPE1, which is a homolog of the Arabidopsis betaVPE gene. OsVPE1 encodes a 497-amino-acid polypeptide. Nucleotide sequence analysis revealed a missense mutation in W379 that changes Cys269 to Gly. Like the wild-type protein, the mutant protein is sorted into vacuoles; however, the enzymatic activity of the mutant OsVPE1 is almost completely eliminated. Further, we show that OsVPE1 is incorrectly cleaved, resulting in a mature protein that is smaller than the wild-type mature protein. Taken together, these results demonstrate that OsVPE1 is a cysteine protease that plays a crucial role in the maturation of rice glutelins. Further, OsVPE1 Cys269 is a key residue for maintaining the Asn-specific cleavage activity of OsVPE1.
authors.affiliation: Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, China.
authors.forename: Yihua
authors.initials: Y
authors.lastname: Wang
authors.forename: Susong
authors.initials: S
authors.lastname: Zhu
authors.forename: Shijia
authors.initials: S
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
authors.forename: Liangming
authors.initials: L
authors.lastname: Chen
authors.forename: Yulong
authors.initials: Y
authors.lastname: Ren
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Han
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Sulan
authors.initials: S
authors.lastname: Ji
authors.forename: Xi
authors.initials: X
authors.lastname: Liu
authors.forename: Jianmin
authors.initials: J
authors.lastname: Wan
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D005983:Glutens / Q000378:metabolism*; D020125:Mutation, Missense; D012275:Oryza / Q000201:enzymology / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics; D017422:Sequence Analysis, DNA; D014617:Vacuoles / Q000201:enzymology*
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant; D005983:Glutens; D003546:Cysteine Endopeptidases