Journal Article

Dual Roles of Photosynthetic Electron Transport in Photosystem I Biogenesis: Light Induction of mRNAs and Chromatic Regulation at Post-mRNA Level

Mitsuhiro Matsuo and Junichi Obokata

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 10, pages 1189-1197
Published in print October 2002 | ISSN: 0032-0781
Published online October 2002 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcf146
Dual Roles of Photosynthetic Electron Transport in Photosystem I Biogenesis: Light Induction of mRNAs and Chromatic Regulation at Post-mRNA Level

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Light regulation of photosystem I (PSI) biogenesis was studied in a unicellular green alga, Chlamydomonas reinhardtii. When Chlamydomonas cells were transferred from darkness to the light, mRNAs for both nuclear- and chloroplast-encoded PSI subunits were induced in concert. This light induction was inhibited by photosynthetic electron transport (PET) inhibitors, 3-(3,4 dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6 isopropyl-p-benzoquinone, but not by an uncoupler, carbonyl cyanide m-chlorophenylhydrazone. This indicated that PET plays a pivotal role in the light induction of PSI subunit mRNAs, but that photophosphorylation is not necessary. When we irradiated the Chlamydomonas cells with PSI-light (695 nm) or PSII-light (644 nm), which makes the plastoquinone pool oxidative and reductive, respectively, PSII-light caused the accumulation of PSI proteins more abundantly than did PSI-light. However, there was no difference for the PSI subunit mRNA levels between these light sources. From these results, we conclude that PET plays dual roles in the regulation of PSI biogenesis in Chlamydomonas: when cells are illuminated, PET first induces the PSI subunit mRNAs irrespective of the redox state of the intersystem electron carriers, and then their redox state fine-tunes PSI biogenesis at translational and/or post-translational steps to fulfil the chromatic adaptation.

Keywords: Keywords: Chlamydomonas — Chromatic adaptation — Photosynthetic electron transport — Photosystem I — Redox regulation.; Abbreviations: CCCP, carbonyl cyanide m-chlorophenylhydrazone; DBMIB, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone; Fm, maximal level of chlorophyll fluorescence; PET, photosynthetic electron transport; PQ, plastoquinone; Redox, reduction/oxidation.

Journal Article.  6124 words.  Illustrated.

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

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