title: Dissecting the Photoprotective Mechanism Encoded by the flv4-2 Operon: a Distinct Contribution of Sll0218 in Photosystem II Stabilization.
abstract: In Synechocystis sp. PCC 6803, the flv4-2 operon encodes the flavodiiron proteins Flv2 and Flv4 together with a small protein, Sll0218, providing photoprotection for Photosystem II (PSII). Here, the distinct roles of Flv2/Flv4 and Sll0218 were addressed, using a number of flv4-2 operon mutants. In the ∆sll0218 mutant, the presence of Flv2/Flv4 rescued PSII functionality as compared with ∆sll0218-flv2, where neither Sll0218 nor the Flv2/Flv4 heterodimer are expressed. Nevertheless, both the ∆sll0218 and ∆sll0218-flv2 mutants demonstrated deficiency in accumulation of PSII proteins suggesting a role for Sll0218 in PSII stabilization, which was further supported by photoinhibition experiments. Moreover, the accumulation of PSII assembly intermediates occurred in Sll0218-lacking mutants. The YFP-tagged Sll0218 protein localized in a few spots per cell at the external side of the thylakoid membrane, and biochemical membrane fractionation revealed clear enrichment of Sll0218 in the PratA-defined membranes, where the early biogenesis steps of PSII occur. Further, the characteristic antenna uncoupling feature of the ∆flv4-2 operon mutants is shown to be related to PSII destabilization in the absence of Sll0218. It is concluded that the Flv2/Flv4 heterodimer supports PSII functionality, while the Sll0218 protein assists PSII assembly and stabilization, including optimization of light harvesting.
authors.affiliation: Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Luca
authors.initials: L
authors.lastname: Bersanini
authors.affiliation: Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Yagut
authors.initials: Y
authors.lastname: Allahverdiyeva
authors.affiliation: Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Natalia
authors.initials: N
authors.lastname: Battchikova
authors.affiliation: Molecular Plant Sciences, Ludwig-Maximillians-Universität München, Biozentrum, Grosshaderner Straße 2-4, 82152, Planegg-Martinsried, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Heinz
authors.affiliation: Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Maija
authors.initials: M
authors.lastname: Lespinasse
authors.affiliation: Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Essi
authors.initials: E
authors.lastname: Ruohisto
authors.affiliation: Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Henna
authors.initials: H
authors.lastname: Mustila
authors.affiliation: Molecular Plant Sciences, Ludwig-Maximillians-Universität München, Biozentrum, Grosshaderner Straße 2-4, 82152, Planegg-Martinsried, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Nickelsen
authors.affiliation: Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, P.O. Box 521, H-6701, Szeged, Hungary.
authors.forename: Imre
authors.initials: I
authors.lastname: Vass
authors.affiliation: Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland.
authors.forename: Eva-Mari
authors.initials: EM
authors.lastname: Aro
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D008027:Light; D009154:Mutation / Q000235:genetics; D009876:Operon / Q000235:genetics*; D010641:Phenotype; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D046939:Synechocystis / Q000378:metabolism* / Q000528:radiation effects*; D020524:Thylakoids / Q000378:metabolism; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D045332:Photosystem II Protein Complex
keywords: Cyanobacteria; Photosystem II repair; flavodiiron proteins; photoprotection; photosynthesis