title: Brassinosteroid-induced CO(2) assimilation is associated with increased stability of redox-sensitive photosynthetic enzymes in the chloroplasts in cucumber plants.
abstract: Brassinosteroids (BRs) play important roles in plant growth, development, photosynthesis and stress tolerance; however, the mechanism underlying BR-enhanced photosynthesis is currently unclear. Here, we provide evidence that an increase in the BR level increased the quantum yield of PSII, activities of Rubisco activase (RCA) and fructose-1,6-bisphosphatase (FBPase), and CO(2) assimilation. BRs upregulated the transcript levels of genes and activity of enzymes involved in the ascorbate-glutathione cycle in the chloroplasts, leading to an increased ratio of reduced (GSH) to oxidized (GSSG) glutathione in the chloroplasts. An increased GSH/GSSG ratio protected RCA from proteolytic digestion and increased the stability of redox-sensitive enzymes in the chloroplasts. These results strongly suggest that BRs are capable of regulating the glutathione redox state in the chloroplasts through the activation of the ascorbate-glutathione cycle. The resulting increase in the chloroplast thiol reduction state promotes CO(2) assimilation, at least in part, by enhancing the stability and activity of redox-sensitive photosynthetic enzymes through post-translational modifications.
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, PR China.
authors.forename: Yu Ping
authors.initials: YP
authors.lastname: Jiang
authors.forename: Fei
authors.initials: F
authors.lastname: Cheng
authors.forename: Yan Hong
authors.initials: YH
authors.lastname: Zhou
authors.forename: Xiao Jian
authors.initials: XJ
authors.lastname: Xia
authors.forename: Wei Hua
authors.initials: WH
authors.lastname: Mao
authors.forename: Kai
authors.initials: K
authors.lastname: Shi
authors.forename: Zhi Xiang
authors.initials: ZX
authors.lastname: Chen
authors.forename: Jing Quan
authors.initials: JQ
authors.lastname: Yu
mesh_terms: D001205:Ascorbic Acid / Q000096:biosynthesis; D060406:Brassinosteroids / Q000096:biosynthesis*; D002245:Carbon Dioxide / Q000378:metabolism*; D002736:Chloroplasts / Q000201:enzymology*; D018553:Cucumis sativus / Q000201:enzymology*; D004579:Electron Transport; D004795:Enzyme Stability; D006597:Fructose-Bisphosphatase / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D005978:Glutathione / Q000096:biosynthesis; D019803:Glutathione Disulfide / Q000378:metabolism; D010084:Oxidation-Reduction; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D010940:Plant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D011499:Protein Processing, Post-Translational; D059748:Proteolysis
chemical_list: D060406:Brassinosteroids; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; C054765:rca protein, plant; D002245:Carbon Dioxide; D006597:Fructose-Bisphosphatase; D005978:Glutathione; D001205:Ascorbic Acid; D019803:Glutathione Disulfide