Journal Article

Nitric Oxide Down-Regulation of Carotenoid Synthesis and PSII Activity in Relation to Very High Light-Induced Singlet Oxygen Production and Oxidative Stress in Chlamydomonas reinhardtii

Hsueh-Ling Chang, Yuan-Ting Hsu, Cheng-Yang Kang and Tse-Min Lee

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 54, issue 8, pages 1296-1315
Published in print August 2013 | ISSN: 0032-0781
Published online June 2013 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pct078
Nitric Oxide Down-Regulation of Carotenoid Synthesis and PSII Activity in Relation to Very High Light-Induced Singlet Oxygen Production and Oxidative Stress in Chlamydomonas reinhardtii

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Nitric oxide (NO) was produced in Chlamydomonas reinhardtii cells 30 min after illumination at a very high light intensity of 3,000 µmol m−2 s−1 (VHL) followed by singlet oxygen (1O2) production, lipid peroxidation, expression of oxidative stress-related genes, irreversible PSII inactivation and cell death. Treatment with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), an NO scavenger, effectively reduced 1O2 levels and VHL damage, while treatment with diphenylamine (DPA), an 1O2 scavenger, only slightly reduced NO levels, though VHL damage was still effectively reduced. In the presence of cPTIO, the decline in minimum (Fo, Ft) and maximum (Fm, Fm′) fluorescence after 60 min of VHL illumination can be slowed, and after recovery to 50 µmol m−2 s−1 conditions, PSII activity (Fv/Fm, Fv′/Fm′) and PSII donor-side and acceptor-side electron transfer were partially restored. This finding indicates that 1O2 production is induced by NO through inhibition of PSII electron transfer under VHL conditions. VHL illumination caused a decrease in carotenoid contents but a transient increase in the transcription of two enzymes involved in carotenoid synthesis, phytoene synthase (PSY) and phytoene desaturase (PDS), at 30 min followed by a decrease at 60 min. The VHL-induced decrease in PDS transcription can be inhibited in the presence of cPTIO. The results of the present study show that NO generated in C. reinhardtii cells under VHL conditions induces 1O2 accumulation due to a decrease in the 1O2-scavenging capacity caused by NO-mediated inhibition of carotenoid synthesis and PSII electron transport, which, in turn, leads to oxidative damage and cell death.

Keywords: Carotenoid; Chlamydomonas reinhardtii; Nitric oxide (NO); Phytoene desaturase (PDS); Phytoene synthase (PSY); PSII electron transfer; Singlet oxygen (1O2); Very high light

Journal Article.  11404 words.  Illustrated.

Subjects: Plant Sciences and Forestry ; Biochemistry ; Molecular and Cell Biology

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