A zeaxanthin-independent nonphotochemical quenching mechanism localized in the photosystem II core complex.
Illumination of dark-adapted barley plants with low light transiently induced a large nonphotochemical quenching of chlorophyll fluorescence. This reaction was identified as a form of high-energy-state quenching. Its appearance was not accompanied by zeaxanthin synthesis but was associated with a reversible inactivation of a fraction of photosystem II (PSII) centers. Both the fluorescence quenching and PSII inactivation relaxed in parallel with the activation of the Calvin cycle. We interpret the induction of this phenomenon as due to the generation of a quenched state in the PSII core complex. This reaction is probably caused by the transient overacidification of the thylakoid lumen, whereas its dissipation results from the relaxation of both the pH gradient across the thylakoid membrane and redox pressure upon activation of carbon fixation. At saturating light intensities, inactivation of PSII was still observed at the onset of illumination, although its recovery did not result in dissipation of high-energy quenching, which presents typical characteristics of an antenna-associated quenching at steady state. Reaction-center quenching seems therefore to be a common transient feature during illumination, being replaced by other phenomena (photochemical or antenna quenching and photoinhibition), depending on the balance between light and carbon fixation fluxes.
Unité Propre de Recherche, 1261 Centre National de la Recherche Scientifique (Associé Université Paris VI), Institut de Biologie Physico Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France. giovanni.finazzi@ibpc.fr
Giovanni
G
Finazzi
Giles N
GN
Johnson
Luca
L
Dall'Osto
Luca
L
Dallosto
Pierre
P
Joliot
Francis-André
FA
Wollman
Roberto
R
Bassi
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D002338:Carotenoids / Q000378:metabolism; D003624:Darkness; D004852:Epoxy Compounds / Q000378:metabolism; D005453:Fluorescence; D001467:Hordeum / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D045342:Light-Harvesting Protein Complexes; D009154:Mutation; D018462:Photobiology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D010940:Plant Proteins; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene / Q000031:analogs & derivatives / Q000378:metabolism
D029681:Arabidopsis Proteins; D004852:Epoxy Compounds; D045342:Light-Harvesting Protein Complexes; C489731:NPQ4 protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; D002338:Carotenoids