Involvement of carotenoids in the synthesis and assembly of protein subunits of photosynthetic reaction centers of Synechocystis sp. PCC 6803

• Published in: Plant and cell physiology 2010-05, Vol.51 (5), p.823-835
• Main Authors: Sozer, O., Hungarian Academy of Sciences, Szeged (Hungary). Biological Research Center, Komenda, J, Ughy, B, Domonkos, I, Laczko-Dobos, H, Malec, P, Gombos, Z, Kis, M
• Format: Article
• Language: English
• Subjects: Alkyl and Aryl Transferases - genetics; Alkyl and Aryl Transferases - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; CAROTENOIDE; CAROTENOIDES; Carotenoidless mutant; CAROTENOIDS; Carotenoids - metabolism; crtB; FOTOSINTESIS; Geranylgeranyl-Diphosphate Geranylgeranyltransferase; http://www.fao.org/aos/agrovoc#c_1333; http://www.fao.org/aos/agrovoc#c_34750; http://www.fao.org/aos/agrovoc#c_5013; http://www.fao.org/aos/agrovoc#c_5812; http://www.fao.org/aos/agrovoc#c_6258; Membrane protein synthesis; MUTANT; MUTANTES; MUTANTS; Mutation; PHOTOSYNTHESE; PHOTOSYNTHESIS; Photosynthetic Reaction Center Complex Proteins - metabolism; PROTEIN SYNTHESIS; PSII assembly; RNA, Bacterial - genetics; SINTESIS DE PROTEINAS; SYNECHOCYSTIS; Synechocystis - genetics; Synechocystis - growth & development; Synechocystis - metabolism; Synechocystis sp. PCC 6803; SYNTHESE PROTEIQUE
• ISSN: 0032-0781; 1471-9053
• DOI: 10.1093/pcp/pcq031

The crtB gene of Synechocystis sp. PCC 6803, encoding phytoene synthase, was inactivated in the deltacrtH mutant to generate a carotenoidless deltacrtH/B double mutant. deltacrtH 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 deltacrtH/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 bsub(6)f 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.