title: Phycobilin/chlorophyll excitation equilibration upon carotenoid-induced non-photochemical fluorescence quenching in phycobilisomes of the cyanobacterium Synechocystis sp. PCC 6803.
abstract: To determine the mechanism of carotenoid-sensitized non-photochemical quenching in cyanobacteria, the kinetics of blue-light-induced quenching and fluorescence spectra were studied in the wild type and mutants of Synechocystis sp. PCC 6803 grown with or without iron. The blue-light-induced quenching was observed in the wild type as well as in mutants lacking PS II or IsiA confirming that neither IsiA nor PS II is required for carotenoid-triggered fluorescence quenching. Both fluorescence at 660 nm (originating from phycobilisomes) and at 681 nm (which, upon 440 nm excitation originates mostly from chlorophyll) was quenched. However, no blue-light-induced changes in the fluorescence yield were observed in the apcE(-) mutant that lacks phycobilisome attachment. The results are interpreted to indicate that interaction of the Slr1963-associated carotenoid with--presumably--allophycocyanin in the phycobilisome core is responsible for non-photochemical energy quenching, and that excitations on chlorophyll in the thylakoid equilibrate sufficiently with excitations on allophycocyanin in wild type to contribute to quenching of chlorophyll fluorescence.
authors.affiliation: A.N. Bakh Institute of Biochemistry, Russian Academy of Sciences, 119071 Moscow, Russia. rakhimberd@inbi.ras.ru
authors.forename: Marina G
authors.initials: MG
authors.lastname: Rakhimberdieva
authors.forename: Dmitrii V
authors.initials: DV
authors.lastname: Vavilin
authors.forename: Wim F J
authors.initials: WF
authors.lastname: Vermaas
authors.forename: Irina V
authors.initials: IV
authors.lastname: Elanskaya
authors.forename: Navassard V
authors.initials: NV
authors.lastname: Karapetyan
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002338:Carotenoids / Q000494:pharmacology*; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008956:Models, Chemical; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D052980:Phycobilins / Q000737:chemistry / Q000378:metabolism*; D045524:Phycobilisomes / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D045332:Photosystem II Protein Complex; D052980:Phycobilins; D045524:Phycobilisomes; D002734:Chlorophyll; D002338:Carotenoids