title: Production of superoxide from Photosystem II in a rice (Oryza sativa L.) mutant lacking PsbS.
abstract: BACKGROUND
  PsbS is a 22-kDa Photosystem (PS) II protein involved in non-photochemical quenching (NPQ) of chlorophyll fluorescence. Rice (Oryza sativa L.) has two PsbS genes, PsbS1 and PsbS2. However, only inactivation of PsbS1, through a knockout (PsbS1-KO) or in RNAi transgenic plants, results in plants deficient in qE, the energy-dependent component of NPQ.
  
  
  RESULTS
  In studies presented here, under fluctuating high light, growth of young seedlings lacking PsbS is retarded, and PSII in detached leaves of the mutants is more sensitive to photoinhibitory illumination compared with the wild type. Using both histochemical and fluorescent probes, we determined the levels of reactive oxygen species, including singlet oxygen, superoxide, and hydrogen peroxide, in leaves and thylakoids. The PsbS-deficient plants generated more superoxide and hydrogen peroxide in their chloroplasts. PSII complexes isolated from them produced more superoxide compared with the wild type, and PSII-driven superoxide production was higher in the mutants. However, we could not observe such differences either in isolated PSI complexes or through PSI-driven electron transport. Time-course experiments using isolated thylakoids showed that superoxide production was the initial event, and that production of hydrogen peroxide proceeded from that.
  
  
  CONCLUSIONS
  These results indicate that at least some of the photoprotection provided by PsbS and qE is mediated by preventing production of superoxide released from PSII under conditions of excess excitation energy.
authors.forename: Ismayil S
authors.initials: IS
authors.lastname: Zulfugarov
authors.forename: Altanzaya
authors.initials: A
authors.lastname: Tovuu
authors.forename: Young-Jae
authors.initials: YJ
authors.lastname: Eu
authors.forename: Bolormaa
authors.initials: B
authors.lastname: Dogsom
authors.forename: Roshan Sharma
authors.initials: RS
authors.lastname: Poudyal
authors.forename: Krishna
authors.initials: K
authors.lastname: Nath
authors.forename: Michael
authors.initials: M
authors.lastname: Hall
authors.forename: Mainak
authors.initials: M
authors.lastname: Banerjee
authors.forename: Ung Chan
authors.initials: UC
authors.lastname: Yoon
authors.forename: Yong-Hwan
authors.initials: YH
authors.lastname: Moon
authors.forename: Gynheung
authors.initials: G
authors.lastname: An
authors.forename: Stefan
authors.initials: S
authors.lastname: Jansson
authors.forename: Choon-Hwan
authors.initials: CH
authors.lastname: Lee
mesh_terms: D002736:Chloroplasts / Q000378:metabolism; D004579:Electron Transport; D005456:Fluorescent Dyes; D005838:Genotype; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D012275:Oryza / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D026082:Singlet Oxygen / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D013481:Superoxides; D026082:Singlet Oxygen; D006861:Hydrogen Peroxide