title: Oxidative stress and photoinhibition can be separated in the cyanobacterium Synechocystis sp. PCC 6803.
abstract: Roles of oxidative stress and photoinhibition in high light acclimation were studied using a regulatory mutant of the cyanobacterium Synechocystis sp. PCC 6803. The mutant strain ΔsigCDE contains the stress responsive SigB as the only functional group 2 σ factor. The ∆sigCDE strain grew more slowly than the control strain in methyl-viologen-induced oxidative stress. Furthermore, a fluorescence dye detecting H2O2, hydroxyl and peroxyl radicals and peroxynitrite, produced a stronger signal in ∆sigCDE than in the control strain, and immunological detection of carbonylated residues showed more protein oxidation in ∆sigCDE than in the control strain. These results indicate that ∆sigCDE suffers from oxidative stress in standard conditions. The oxidative stress may be explained by the findings that ∆sigCDE had a low content of glutathione and low amount of Flv3 protein functioning in the Mehler-like reaction. Although ∆sigCDE suffers from oxidative stress, up-regulation of photoprotective carotenoids and Flv4, Sll2018, Flv2 proteins protected PSII against light induced damage by quenching singlet oxygen more efficiently in ∆sigCDE than in the control strain in visible and in UV-A/B light. However, in UV-C light singlet oxygen is not produced and PSII damage occurred similarly in the ∆sigCDE and control strains. According to our results, resistance against the light-induced damage of PSII alone does not lead to high light tolerance of the cells, but in addition efficient protection against oxidative stress would be required.
authors.affiliation: Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
authors.forename: Kaisa
authors.initials: K
authors.lastname: Hakkila
authors.affiliation: Department of Biochemistry, University of Turku, FI-20014 Turku, Finland; Biological Faculty, Moscow State University, Vorobyevi Gory 119992, Moscow, Russia.
authors.forename: Taras
authors.initials: T
authors.lastname: Antal
authors.affiliation: Institute of Plant Biology, Biological Research Centre of Hungarian Academy of Sciences, P. O. Box 521, H-6701 Szeged, Hungary.
authors.forename: Ateeq Ur
authors.initials: AU
authors.lastname: Rehman
authors.affiliation: Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Kurkela
authors.affiliation: Department of Life Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Wada
authors.affiliation: Institute of Plant Biology, Biological Research Centre of 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, University of Turku, FI-20014 Turku, Finland.
authors.forename: Esa
authors.initials: E
authors.lastname: Tyystjärvi
authors.affiliation: Department of Biochemistry, University of Turku, FI-20014 Turku, Finland. Electronic address: taityy@utu.fi.
authors.forename: Taina
authors.initials: T
authors.lastname: Tyystjärvi
mesh_terms: D002338:Carotenoids / Q000378:metabolism; D004579:Electron Transport / Q000187:drug effects / Q000528:radiation effects; D050356:Lipid Metabolism / Q000187:drug effects / Q000528:radiation effects; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects*; D055668:Photochemical Processes / Q000187:drug effects / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D020011:Protective Agents / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D046939:Synechocystis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D045332:Photosystem II Protein Complex; D020011:Protective Agents; D013481:Superoxides; D002338:Carotenoids
keywords: 2,6-dichloro-p-benzoquinone; 3-(3,4-dichlorophenyl)-1,1-dimethylurea Photosystems I, PSI; 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate; CM-H(2)DCFDA; CS; Chl; DCBQ; DCMU; High light; Oxidative stress; PPFD; PSII; Photoinhibition; Photosystem II; ROS; Reactive oxygen species (ROS); Sigma factor; chlorophyll; glucose tolerant control strain of Synechocystis sp. PCC 6803; k(PI); photosynthetic photon flux density; rate constant of photoinhibition; reactive oxygen species