title: Efficient operation of NAD(P)H dehydrogenase requires supercomplex formation with photosystem I via minor LHCI in Arabidopsis.
abstract: In higher plants, the chloroplast NAD(P)H dehydrogenase (NDH) complex mediates photosystem I (PSI) cyclic and chlororespiratory electron transport. We reported previously that NDH interacts with the PSI complex to form a supercomplex (NDH-PSI). In this study, NDH18 and FKBP16-2 (FK506 Binding Protein 16-2), detected in the NDH-PSI supercomplex by mass spectrometry, were shown to be NDH subunits by the analysis of their knockdown lines. On the basis of extensive mutant characterization, we propose a structural model for chloroplast NDH, whereby NDH is divided into four subcomplexes. The subcomplex A and membrane subcomplex are conserved in cyanobacteria, but the subcomplex B and lumen subcomplex are specific to chloroplasts. Two minor light-harvesting complex I proteins, Lhca5 and Lhca6, were required for the full-size NDH-PSI supercomplex formation. Similar to crr pgr5 double mutants that completely lack cyclic electron flow activity around PSI, the lhca6 pgr5 double mutant exhibited a severe defect in growth. Consistent with the impaired NDH activity, photosynthesis was also severely affected in mature leaves of lhca6 pgr5. We conclude that chloroplast NDH became equipped with the novel subcomplexes and became associated with PSI during the evolution of land plants, and this process may have facilitated the efficient operation of NDH.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, Japan.
authors.forename: Lianwei
authors.initials: L
authors.lastname: Peng
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Fukao
authors.forename: Masayuki
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Tsuneaki
authors.initials: T
authors.lastname: Takami
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D046911:Macromolecular Substances / Q000378:metabolism; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C493777:Lhca5 protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; C465062:PGR5 protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D009252:NADPH Dehydrogenase