title: Rice GDP-mannose pyrophosphorylase OsVTC1-1 and OsVTC1-3 play different roles in ascorbic acid synthesis.
abstract: GDP-D-mannose pyrophosphorylase (GMPase) catalyzes the synthesis of GDP-D-mannose, which is a precursor for ascorbic acid (AsA) synthesis in plants. The rice genome encodes three GMPase homologs OsVTC1-1, OsVTC1-3 and OsVTC1-8, but their roles in AsA synthesis are unclear. The overexpression of OsVTC1-1 or OsVTC1-3 restored the AsA synthesis of vtc1-1 in Arabidopsis, while that of OsVTC1-8 did not, indicating that only OsVTC1-1 and OsVTC1-3 are involved in AsA synthesis in rice. Similar to Arabidopsis VTC1, the expression of OsVTC1-1 was high in leaves, induced by light, and inhibited by dark. Unlike OsVTC1-1, the expression level of OsVTC1-3 was high in roots and quickly induced by the dark, while the transcription level of OsVTC1-8 did not show obvious changes under constant light or dark treatments. In OsVTC1-1 RNAi plants, the AsA content of rice leaves decreased, and the AsA production induced by light was limited. In contrast, OsVTC1-3 RNAi lines altered AsA synthesis levels in rice roots, but not in the leaves or under the light/dark treatment. The enzyme activity showed that OsVTC1-1 and OsVTC1-3 had higher GMPase activities than OsVTC1-8 in vitro. Our data showed that, unlike in Arabidopsis, the rice GPMase homologous proteins illustrated a new model in AsA synthesis: OsVTC1-1 may be involved in the AsA synthesis, which takes place in leaves, while OsVTC1-3 may be responsible for AsA synthesis in roots. The different roles of rice GMPase homologous proteins in AsA synthesis may be due to their differences in transcript levels and enzyme activities.
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.|National Key Facility of Crop Gene Resources and Genetic Improvement, Beijing, 100081, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Qin
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.|Hainan Academy of Agricultural Sciences, Haikou, 571000, China.
authors.forename: Zaian
authors.initials: Z
authors.lastname: Deng
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.|Hainan Academy of Agricultural Sciences, Haikou, 571000, China.
authors.forename: Chuanyu
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.|National Key Facility of Crop Gene Resources and Genetic Improvement, Beijing, 100081, China.
authors.forename: Yayun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.|National Key Facility of Crop Gene Resources and Genetic Improvement, Beijing, 100081, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Biology, University of Virginia, Charlottesville, VA, 22903, USA.
authors.forename: Hai
authors.initials: H
authors.lastname: Liu
authors.affiliation: Hainan Academy of Agricultural Sciences, Haikou, 571000, China.
authors.forename: Zhili
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China. rfhuang@caas.cn.|National Key Facility of Crop Gene Resources and Genetic Improvement, Beijing, 100081, China. rfhuang@caas.cn.
authors.forename: Rongfeng
authors.initials: R
authors.lastname: Huang
authors.affiliation: Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China. zhangzhijin@caas.cn.|National Key Facility of Crop Gene Resources and Genetic Improvement, Beijing, 100081, China. zhangzhijin@caas.cn.
authors.forename: Zhijin
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001205:Ascorbic Acid / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D009713:Nucleotidyltransferases; C026917:mannose 1-phosphate guanylyltransferase; D001205:Ascorbic Acid
keywords: Ascorbic acid; GDP-D-mannose pyrophosphorylase; L-galactose pathway; Rice