Enhanced Ascorbate Regeneration Via Dehydroascorbate Reductase Confers Tolerance to Photo-Oxidative Stress in Chlamydomonas reinhardtii. (20th July 2016)

• Record Type: Journal Article
• Authors: Lin, Shu-Tseng; Chiou, Chih-Wen; Chu, Yen-Lin; Hsiao, Yu; Tseng, Yu-Fei; Chen, Yi-Chun; Chen, Hsien-Jung; Chang, Hsin-Yang; Lee, Tse-Min
• Is Part Of: Plant & cell physiology. Volume 57:Number 10(2016:Oct.)
• Page Start: 2104
• Page End: 2121
• Publication Date: 2016-07-20
• Subjects: Ascorbate -- Ascorbate–glutathione cycle -- Chlamydomonas -- Dehydroascorbate reductase -- High-intensity light stress; Plant physiology -- Periodicals; Microbiology -- Periodicals; Cytology -- Periodicals; Cell Physiology -- Periodicals; Plant Physiological Phenomena -- Periodicals; Cytology; Microbiology; Plant physiology; Periodicals; 571.205
• DOI: 10.1093/pcp/pcw129
• Languages: English
• ISSNs: 0032-0781

Abstract

Abstract: The role of ascorbate (AsA) recycling via dehydroascorbate reductase (DHAR) in the tolerance of Chlamydomonas reinhardtii to photo-oxidative stress was examined. The activity of DHAR and the abundance of the CrDHAR1 (Cre10.g456750) transcript increased after moderate light (ML; 750 µmol m –2 s –1 ) or high light (HL; 1, 800 µmol m –2 s –1 ) illumination, accompanied by dehydroascorbate (DHA) accumulation, decreased AsA redox state, photo-inhibition, lipid peroxidation, H2 O2 overaccumulation, growth inhibition and cell death. It suggests that DHAR and AsA recycling is limiting under high-intensity light stress. The CrDHAR1 gene was cloned and its recombinant CrDHAR1 protein was a monomer (25 kDa) detected by Western blot that exhibits an enzymatic activity of 965 µmol min –1 mg –1 protein. CrDHAR1 was overexpressed driven by a HSP70A:RBCS2 fusion promoter or down-regulated by artificial microRNA (amiRNA) to examine whether DHAR-mediated AsA recycling is critical for the tolerance of C. reinahartii cells to photo-oxidative stress. The overexpression of CrDHAR1 increased DHAR protein abundance and enzyme activity, AsA pool size, AsA:DHA ratio and the tolerance to ML-, HL-, methyl viologen- or H2 O2 -induced oxidative stress. The CrDHAR1 -knockdown amiRNA lines that have lower DHAR expression and AsA recycling ability were sensitive to high-intensity illumination and oxidative stress. The glutathione pool size, glutathione:oxidized glutathione ratio and glutathione reductase and ascorbate peroxidase activities were increased in CrDHAR1 -overexpressing cells and showed a further increase after high-intensity illumination but decreased in wild-type cells after light stress. The present results suggest that increasing AsA regeneration via enhanced DHAR activity modulates the ascorbate–glutathione cycle activity in C. reinhardtii against photo-oxidative stress.