title: The UV-B photoreceptor UVR8 promotes photosynthetic efficiency in Arabidopsis thaliana exposed to elevated levels of UV-B.
abstract: The UV-B photoreceptor UVR8 regulates expression of genes in response to UV-B, some encoding chloroplast proteins, but the importance of UVR8 in maintaining photosynthetic competence is unknown. The maximum quantum yield of PSII (F (v)/F(m)) and the operating efficiency of PSII (Φ(PSII)) were measured in wild-type and uvr8 mutant Arabidopsis thaliana. The importance of specific UVR8-regulated genes in maintaining photosynthetic competence was examined using mutants. Both F (v)/F(m) and Φ(PSII) decreased when plants were exposed to elevated UV-B, in general more so in uvr8 mutant plants than wild-type. UV-B increased the level of psbD-BLRP (blue light responsive promoter) transcripts, encoding the PSII D2 protein. This increase was mediated by the UVR8-regulated chloroplast RNA polymerase sigma factor SIG5, but SIG5 was not required to maintain photosynthetic efficiency at elevated UV-B. Levels of the D1 protein of PSII decreased markedly when plants were exposed to elevated UV-B, but there was no significant difference between wild-type and uvr8 under conditions where the mutant showed increased photoinhibition. The results show that UVR8 promotes photosynthetic efficiency at elevated levels of UV-B. Loss of the DI polypeptide is probably important in causing photoinhibition, but does not entirely explain the reduced photosynthetic efficiency of the uvr8 mutant compared to wild-type.
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Davey
authors.forename: Novita I
authors.initials: NI
authors.lastname: Susanti
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Wargent
authors.forename: Jane E
authors.initials: JE
authors.lastname: Findlay
authors.forename: W
authors.initials: W
authors.lastname: Paul Quick
authors.forename: Nigel D
authors.initials: ND
authors.lastname: Paul
authors.forename: Gareth I
authors.initials: GI
authors.lastname: Jenkins
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000502:physiology / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009154:Mutation; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D013472:Sunlight; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; D002868:Chromosomal Proteins, Non-Histone; C078410:ELIP protein, Arabidopsis; D045332:Photosystem II Protein Complex; C486979:Sig5 protein, Arabidopsis; D012808:Sigma Factor; C525052:Uvr8 protein, Arabidopsis