title: Sharing light between two photosystems: mechanism of state transitions.
abstract: In the thylakoid membrane, the two photosystems act in series to promote linear electron flow, with the concomitant production of ATP and reducing equivalents such as NADPH. Photosystem I, which is preferentially activated in far-red light, also energizes cyclic electron flow which generates only ATP. Thus, changes in light quality and cellular metabolic demand require a rapid regulation of the activity of the two photosystems. At low light intensities, this is mediated by state transitions. They allow the dynamic allocation of light harvesting antennae to the two photosystems, regulated through protein phosphorylation by a kinase and phosphatase pair that respond to the redox state of the electron transfer chain. Phosphorylation of the antennae leads to remodeling of the photosynthetic complexes.
authors.affiliation: Department of Botany and Plant Biology, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneva 4, Switzerland. Electronic address: michel.goldschmidt-clermont@unige.ch.
authors.forename: Michel
authors.initials: M
authors.lastname: Goldschmidt-Clermont
authors.affiliation: Dipartimento di Biotecnologie, Università degli Studi di Verona, 15, strada Le Grazie, 37134 Verona, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Bassi
mesh_terms: D002696:Chlamydomonas / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D010084:Oxidation-Reduction; D010766:Phosphorylation; D045331:Photosystem I Protein Complex / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000528:radiation effects*; D010944:Plants / Q000378:metabolism* / Q000528:radiation effects; D020524:Thylakoids / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex