title: A dual strategy to cope with high light in Chlamydomonas reinhardtii.
abstract: Absorption of light in excess of the capacity for photosynthetic electron transport is damaging to photosynthetic organisms. Several mechanisms exist to avoid photodamage, which are collectively referred to as nonphotochemical quenching. This term comprises at least two major processes. State transitions (qT) represent changes in the relative antenna sizes of photosystems II and I. High energy quenching (qE) is the increased thermal dissipation of light energy triggered by lumen acidification. To investigate the respective roles of qE and qT in photoprotection, a mutant (npq4 stt7-9) was generated in Chlamydomonas reinhardtii by crossing the state transition-deficient mutant (stt7-9) with a strain having a largely reduced qE capacity (npq4). The comparative phenotypic analysis of the wild type, single mutants, and double mutants reveals that both state transitions and qE are induced by high light. Moreover, the double mutant exhibits an increased photosensitivity with respect to the single mutants and the wild type. Therefore, we suggest that besides qE, state transitions also play a photoprotective role during high light acclimation of the cells, most likely by decreasing hydrogen peroxide production. These results are discussed in terms of the relative photoprotective benefit related to thermal dissipation of excess light and/or to the physical displacement of antennas from photosystem II.
authors: Centre National Recherche Scientifique, Unité Mixte Recherche 5168, Laboratoire Physiologie Cellulaire et Végétale, F-38054 Grenoble, France.
authors: Guillaume
authors: G
authors: Allorent
authors: Ryutaro
authors: R
authors: Tokutsu
authors: Thomas
authors: T
authors: Roach
authors: Graham
authors: G
authors: Peers
authors: Pierre
authors: P
authors: Cardol
authors: Jacqueline
authors: J
authors: Girard-Bascou
authors: Daphné
authors: D
authors: Seigneurin-Berny
authors: Dimitris
authors: D
authors: Petroutsos
authors: Marcel
authors: M
authors: Kuntz
authors: Cécile
authors: C
authors: Breyton
authors: Fabrice
authors: F
authors: Franck
authors: Francis-André
authors: FA
authors: Wollman
authors: Krishna K
authors: KK
authors: Niyogi
authors: Anja
authors: A
authors: Krieger-Liszkay
authors: Jun
authors: J
authors: Minagawa
authors: Giovanni
authors: G
authors: Finazzi
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000502:physiology*; D005453:Fluorescence; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009550:Nigericin / Q000494:pharmacology; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D017346:Protein Serine-Threonine Kinases; D009550:Nigericin