Journal Article

Involvement of Carotenoids in the Synthesis and Assembly of Protein Subunits of Photosynthetic Reaction Centers of <i>Synechocystis</i> sp. PCC 6803

Ozge Sozer, Josef Komenda, Bettina Ughy, Ildikó Domonkos, Hajnalka Laczkó-Dobos, Przemyslaw Malec, Zoltán Gombos and Mihály Kis

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 5, pages 823-835
Published in print May 2010 | ISSN: 0032-0781
Published online March 2010 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcq031
Involvement of Carotenoids in the Synthesis and Assembly of Protein Subunits of Photosynthetic Reaction Centers of Synechocystis sp. PCC 6803

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The crtB gene of Synechocystis sp. PCC 6803, encoding phytoene synthase, was inactivated in the ΔcrtH mutant to generate a carotenoidless ΔcrtH/B double mutant. ΔcrtH mutant cells were used because they had better transformability than wild-type cells, most probably due to their adaptation to partial carotenoid deficiency. Cells of the ΔcrtH/B mutant were light sensitive and could grow only under light-activated heterotrophic growth conditions in the presence of glucose. Carotenoid deficiency did not significantly affect the cellular content of phycobiliproteins while the chlorophyll content of the mutant cells decreased. The mutant cells exhibited no oxygen-evolving activity, suggesting the absence of photochemically active PSII complexes. This was confirmed by 2D electrophoresis of photosynthetic membrane complexes. Analyses identified only a small amount of a non-functional PSII core complex lacking CP43, while the monomeric and dimeric PSII core complexes were absent. On the other hand, carotenoid deficiency did not prevent formation of the cytochrome b6f complex and PSI, which predominantly accumulated in the monomeric form. Radioactive labeling revealed very limited synthesis of inner PSII antennae, CP47 and especially CP43. Thus, carotenoids are indispensable constituents of the photosynthetic apparatus, being essential not only for antioxidative protection but also for the efficient synthesis and accumulation of photosynthetic proteins and especially that of PSII antenna subunits.

Keywords: Carotenoidless mutant; crtB; Membrane protein synthesis; Photosynthesis; PSII assembly; Synechocystis sp. PCC 6803

Journal Article.  7927 words.  Illustrated.

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

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