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Brassinosteroid-induced CO2 assimilation is associated with increased stability of redox-sensitive photosynthetic enzymes in the chloroplasts in cucumber plants

Authors
Journal
Biochemical and Biophysical Research Communications
0006-291X
Publisher
Elsevier
Publication Date
Volume
426
Issue
3
Identifiers
DOI: 10.1016/j.bbrc.2012.08.100
Keywords
  • Benson-Calvin Cycle
  • Cucumis Sativus
  • Glutathione
  • Photosynthesis
  • Reactive Oxygen Species
  • Redox Homeostasis
Disciplines
  • Biology
  • Physics

Abstract

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 CO2 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 CO2 assimilation, at least in part, by enhancing the stability and activity of redox-sensitive photosynthetic enzymes through post-translational modifications.

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