Chloroplast NAD kinase is essential for energy transduction through the xanthophyll cycle in photosynthesis.
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.
Takahashi
Hideyuki
H
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
Watanabe
Ayako
A
Tanaka
Ayumi
A
Hashida
Shin-Nosuke
SN
Kawai-Yamada
Maki
M
Sonoike
Kintake
K
Uchimiya
Hirofumi
H
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
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