title: New subunits NDH-M, -N, and -O, encoded by nuclear genes, are essential for plastid Ndh complex functioning in higher plants.
abstract: In higher plants, the Ndh complex reduces plastoquinones and is involved in cyclic electron flow around photosystem I, supplying extra-ATP for photosynthesis, particularly under environmental stress conditions. Based on plastid genome sequences, the Ndh complex would contain 11 subunits (NDH-A to -K), but homologies with bacterial complex indicate the probable existence of additional subunits. To identify missing subunits, tobacco (Nicotiana tabacum) NDH-H was His tagged at its N terminus using plastid transformation. A functional Ndh subcomplex was purified by Ni(2+) affinity chromatography and its subunit composition analyzed by mass spectrometry. Five plastid encoded subunits (NDH-A, -H, -I, -J, and -K) were identified as well as three new subunits (NDH-M, -N, and -O) homologous to cyanobacterial and higher plant proteins. Arabidopsis thaliana mutants missing one of these new subunits lack a functional Ndh complex, and NDH-M and NDH-N are not detected in a tobacco transformant lacking the Ndh complex. We discuss the involvement of these three nuclear-encoded subunits in the functional integrity of the plastidial complex.
authors.affiliation: Département d'Ecophysiologie Végétale et de Microbiologie, Laboratoire d'Ecophysiologie de la Photosynthèse, Centre National de la Recherche Scientifique, Université de la Méditerranée, Saint-Paul-lez-Durance, France. dominique.rumeau@cea.fr
authors.forename: Dominique
authors.initials: D
authors.lastname: Rumeau
authors.forename: Noëlle
authors.initials: N
authors.lastname: Bécuwe-Linka
authors.forename: Audrey
authors.initials: A
authors.lastname: Beyly
authors.forename: Mathilde
authors.initials: M
authors.lastname: Louwagie
authors.forename: Jérôme
authors.initials: J
authors.lastname: Garin
authors.forename: Gilles
authors.initials: G
authors.lastname: Peltier
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics*; D045222:Electron Transport Chain Complex Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis / Q000235:genetics; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018087:Plastids / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism
chemical_list: D045222:Electron Transport Chain Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D021122:Protein Subunits; D009252:NADPH Dehydrogenase