Journal Article

Photoinhibition and Light-Induced Cyclic Electron Transport in <i>ndhB</i><sup>–</sup> and <i>psaE</i><sup>–</sup> Mutants of <i>Synechocystis</i> sp. PCC 6803

David J. Thomas, Jannette Thomas, Philip A. Youderian and Stephen K. Herbert

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 8, pages 803-812
Published in print August 2001 | ISSN: 0032-0781
Published online August 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce104
Photoinhibition and Light-Induced Cyclic Electron Transport in ndhB– and psaE– Mutants of Synechocystis sp. PCC 6803

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The ndhB and psaE mutants of the cyanobacterium Synechocystis sp. PCC 6803 are partly deficient in PSI-driven cyclic electron transport. We compared photoinhibition in these mutants to the wild type to test the hypothesis that PSI cyclic electron transport protects against photoinhibition. Photoinhibitory treatment greatly accelerated PSI cyclic electron transport in the wild type and also in both the mutants. The psaE mutant showed rates of PSI cyclic electron transport similar to the wild type under all conditions tested. The ndhB mutant showed much lower rates of PSI cyclic electron transport than the wild type following brief dark adaptation but exceeded wild type rates after exposure to photoinhibitory light. The wild type and both mutants showed similar rates of photoinhibition damage and photoinhibition repair at PSII. Photoinhibition at PSI was much slower than at PSII and was also similar between the wild type and both mutants, despite the known instability of PSI in the psaE mutant. We conclude that photoinhibitory light induces sufficient PSI-driven cyclic electron transport in both the ndhB and psaE mutants to fulfill any role that cyclic electron transport plays in protection against photoinhibition.

Keywords: Key words: Cyanobacteria — ndhB — Photoinhibition — Photosynthesis — psaE — PSI cyclic electron transport.; Abbreviations: ΔS820, the change in reflectance signal at 820 nm that results from photooxidation of P700; DMBQ, 2,6-dimethylbenzoquinone; FQR, the putative ferredoxin-quinone oxidoreductase; KFeCN, potassium ferricyanide; MV, methyl viologen (paraquat); NDH-1, the thylakoid NAD(P)H dehydrogenase; PAR, photosynthetically active radiation; PET, photosynthetic electron transport.

Journal Article.  7563 words.  Illustrated.

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

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