title: Chloroplast NAD kinase is essential for energy transduction through the xanthophyll cycle in photosynthesis.
abstract: Photosynthetic parameters of the nadk2 mutant of Arabidopsis thaliana, which is defective in chloroplast NAD kinase, were investigated. In this plant, the effective efficiency of photosynthetic electron transport (PhiII) and the quantum yield of open reaction centers of photosystem II (Fv'/Fm') were decreased. Furthermore, an increase in non-photochemical quenching attributed to energy dissipation from the xanthophyll cycle was observed. The mutant showed an aberrant de-epoxidation state of xanthophyll cycle carotenoids and had a high level of zeaxanthin even under low light conditions. These results indicate that chloroplast NAD kinase, catalyzing phosphorylation of NAD, is essential for the proper photosynthetic machinery of PSII and the xanthophyll cycle.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan. yany@iam.u-tokyo.ac.jp
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Ayako
authors.initials: A
authors.lastname: Watanabe
authors.forename: Ayumi
authors.initials: A
authors.lastname: Tanaka
authors.forename: Shin-Nosuke
authors.initials: SN
authors.lastname: Hashida
authors.forename: Maki
authors.initials: M
authors.lastname: Kawai-Yamada
authors.forename: Kintake
authors.initials: K
authors.lastname: Sonoike
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Uchimiya
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology*; D004579:Electron Transport / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D009154:Mutation / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D024341:Xanthophylls / Q000378:metabolism*; D065146:Zeaxanthins
chemical_list: D029681:Arabidopsis Proteins; D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D065146:Zeaxanthins; D002338:Carotenoids; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase; C518663:NADK2 protein, Arabidopsis