Journal Article

Effects of Low CO<sub>2</sub> on NAD(P)H Dehydrogenase, a Mediator of Cyclic Electron Transport Around Photosystem I in the Cyanobacterium <i>Synechocystis</i> PCC6803

Yong Deng, Jiyu Ye and Hualing Mi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 5, pages 534-540
Published in print May 2003 | ISSN: 0032-0781
Published online May 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg067
Effects of Low CO2 on NAD(P)H Dehydrogenase, a Mediator of Cyclic Electron Transport Around Photosystem I in the Cyanobacterium Synechocystis PCC6803

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The expression and activity of type-1 NAD(P)H dehydrogenase (NDH-1) was compared between cells of Synechocystis PCC6803 grown in high (H-cells) and low (L-cells) CO2 conditions. Western analysis indicated that L-cells contain higher amounts of the NDH-1 subunits, NdhH, NdhI and NdhK. An NADPH-specific subcomplex of NDH-1 showed higher NADPH-nitroblue tetrazolium oxidoreductase activity in L-cells. The activities of both NADPH-menadione oxidoreductase and light-dependent NADPH oxidation driven by photosystem I were much higher in L-cells than in H-cells. The initial rate of re-reduction of P700+ following actinic light illumination in the presence of DCMU under background far-red light was enhanced in L-cells. In addition, rotenone, a specific inhibitor of NDH-1, suppressed the relative rate of post-illumination increase in Chl fluorescence of L-cells more than that of H-cells, suggesting that the involvement of NDH-1 in cyclic electron flow around photosystem I was enhanced by low CO2. Taken together, these results suggest that NDH-1 complex and NDH-1-mediated cyclic electron transport are stimulated by low CO2 and function in the acclimation of cyanobacteria to low CO2.

Keywords: Keywords: Carbon dioxide — NAD(P)H dehydrogenase — PSI-cyclic electron transport — Synechocystis PCC6803.; Abbreviations: H-cells, cells grown in 2% CO2; L-cells, cells grown in air; NBT, nitroblue tetrazolium; NDH-1, NAD(P)H dehydrogenase; P700, the reaction center chlorophylls in PSI; PMSF, phenylmethylsulfonyl fluoride; RFp, initial rate of post-illumination increase in chlorophyll fluorescence; Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase.

Journal Article.  4478 words.  Illustrated.

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

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