New subunits NDH-M, -N, and -O, encoded by nuclear genes, are essential for plastid Ndh complex functioning in higher plants.
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.
Rumeau
Dominique
D
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
Bécuwe-Linka
Noëlle
N
Beyly
Audrey
A
Louwagie
Mathilde
M
Garin
Jérôme
J
Peltier
Gilles
G
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
D045222:Electron Transport Chain Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D021122:Protein Subunits; D009252:NADPH Dehydrogenase