TAILIEUCHUNG - Báo cáo khoa học: Photosynthetic acclimation: Does the dynamic structure and macro-organisation of photosystem II in higher plant grana membranes regulate light harvesting states?

The efficiency of light harvesting in higher plant photosynthesis is regulated in response to external environmental conditions. Under conditions of excess light, the normally highly efficient light-harvesting system of photo-system II is switched into a state in which unwanted, potentially harmful, energy is dissipated as heat. | ỊFEBS Journal MINIREVIEW Photosynthetic acclimation Does the dynamic structure and macro-organisation of photosystem II in higher plant grana membranes regulate light harvesting states Peter Horton1 Matthew P. Johnson2 Maria L. Perez-Bueno1 Anett Z. Kiss1 and Alexander V. Ruban2 1 Department of Molecular Biology and Biotechnology University of Sheffield UK 2 Schoolof Biologicaland ChemicalSciences Queen Mary University of London UK Keywords Arabidopsis chloroplast grana membranes LHCII nonphotochemical quenching photoprotection photosynthesis PSII thylakoid membrane xanthophyll cycle Correspondence P. Horton Department of Molecular Biology and Biotechnology University of Sheffield Western Bank Sheffield S10 2TN UK Fax 44 0 114 222 2712 Tel 44 0 114 222 4189 E-mail Website http photosynthesis. Received 21 September 2007 accepted 30 November 2007 The efficiency of light harvesting in higher plant photosynthesis is regulated in response to external environmental conditions. Under conditions of excess light the normally highly efficient light-harvesting system of photosystem II is switched into a state in which unwanted potentially harmful energy is dissipated as heat. This process known as nonphotochemical quenching occurs by the creation of energy quenchers following conformational change in the light-harvesting complexes which is initiated by the build up of the thylakoid pH gradient and controlled by the xanthophyll cycle. In the present study the evidence to support the notion that this regulatory mechanism is dependent upon the organization of the different antenna subunits in the stacked grana membranes is reviewed. We postulate that nonphotochemical quenching occurs within a structural locus comprising the PsbS subunit and components of the light-harvesting antenna CP26 CP24 CP29 and LHCIIb the major trimeric light-harvesting complex formed in response to protonation and controlled by the xanthophyll cycle carotenoids. .

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