title: Role of visible light in the recovery of photosystem II structure and function from ultraviolet-B stress in higher plants.
abstract: The effect of visible light on photosystem II reaction centre D1 protein in plants treated with ultraviolet-B light was studied. It was found that a 20 kDa C-terminal fragment of D1 protein generated during irradiation with ultraviolet-B light was stable when plants were incubated in the dark, but was degraded when plants were incubated in visible light. In this condition the recovery of photosynthetic activity was also observed. Even a low level of white light was sufficient to promote both further degradation of the fragment and recovery of activity. During this phase, the D1 protein is the main synthesized thylakoid polypeptide, indicating that other photosystem II proteins are recycled in the recovery process. Although both degradation of the 20 kDa fragment and resynthesis of D1 are light-dependent phenomena, they are not closely related, as degradation of the 20 kDa fragment may occur even in the absence of D1 synthesis. Comparing chemical and physical factors affecting the formation of the fragment in ultraviolet-B light and its degradation in white light, it was concluded that the formation of the fragment in ultraviolet-B light is a photochemical process, whereas the degradation of the fragment in white light is a protease-mediated process.
authors.affiliation: Dipartimento di Biologia, Università di Padova, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Bergo
authors.forename: Anna
authors.initials: A
authors.lastname: Segalla
authors.forename: Giorgio Mario
authors.initials: GM
authors.lastname: Giacometti
authors.forename: Delia
authors.initials: D
authors.lastname: Tarantino
authors.forename: Carlo
authors.initials: C
authors.lastname: Soave
authors.forename: Flora
authors.initials: F
authors.lastname: Andreucci
authors.forename: Roberto
authors.initials: R
authors.lastname: Barbato
mesh_terms: D008027:Light; D008034:Lincomycin / Q000494:pharmacology; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D045332:Photosystem II Protein Complex; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D010940:Plant Proteins / Q000378:metabolism / Q000528:radiation effects; D020524:Thylakoids / Q000502:physiology / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D008034:Lincomycin