title: The PsbZ subunit of Photosystem II in Synechocystis sp. PCC 6803 modulates electron flow through the photosynthetic electron transfer chain.
abstract: The psbZ gene of Synechocystis sp. PCC 6803 encodes the approximately 6.6 kDa photosystem II (PSII) subunit. We here report biophysical, biochemical and in vivo characterization of Synechocystis sp. PCC 6803 mutants lacking psbZ. We show that these mutants are able to perform wild-type levels of light-harvesting, energy transfer, PSII oxygen evolution, state transitions and non-photochemical quenching (NPQ) under standard growth conditions. The mutants grow photoautotrophically; however, their growth rate is clearly retarded under low-light conditions and they are not capable of photomixotrophic growth. Further differences exist in the electron transfer properties between the mutants and wild type. In the absence of PsbZ, electron flow potentially increased through photosystem I (PSI) without a change in the maximum electron transfer capacity of PSII. Further, rereduction of P700(+) is much faster, suggesting faster cyclic electron flow around PSI. This implies a role for PsbZ in the regulation of electron transfer, with implication for photoprotection.
authors.affiliation: Photosynthesis Research Group, Department of Biology, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK.
authors.forename: Cleo L
authors.initials: CL
authors.lastname: Bishop
authors.forename: Simin
authors.initials: S
authors.lastname: Ulas
authors.forename: Elena
authors.initials: E
authors.lastname: Baena-Gonzalez
authors.forename: Eva-Mari
authors.initials: EM
authors.lastname: Aro
authors.forename: Saul
authors.initials: S
authors.lastname: Purton
authors.forename: Jonathan H A
authors.initials: JH
authors.lastname: Nugent
authors.forename: Pirkko
authors.initials: P
authors.lastname: Mäenpää
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D003624:Darkness; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D004583:Electrons; D007425:Intracellular Membranes / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010641:Phenotype; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D046939:Synechocystis / Q000254:growth & development / Q000378:metabolism*; D013696:Temperature; D020524:Thylakoids / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D045332:Photosystem II Protein Complex; D021122:Protein Subunits; D010100:Oxygen