Journal Article

A Novel Nuclear-Encoded Protein, NDH-Dependent Cyclic Electron Flow 5, is Essential for the Accumulation of Chloroplast NAD(P)H Dehydrogenase Complexes

Satoshi Ishida, Atsushi Takabayashi, Noriko Ishikawa, Yasushi Hano, Tsuyoshi Endo and Fumihiko Sato

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 2, pages 383-393
Published in print February 2009 | ISSN: 0032-0781
Published online January 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn205
A Novel Nuclear-Encoded Protein, NDH-Dependent Cyclic Electron Flow 5, is Essential for the Accumulation of Chloroplast NAD(P)H Dehydrogenase Complexes

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  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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The chloroplast NAD(P)H dehydrogenase (NDH) complex, which reduces plastoquinones in thylakoid membranes, is involved in PSI cyclic electron flow and chlororespiration. In addition to land plants, the NDH complex is conserved in cyanobacteria. In this study, we identified a novel NDH-related gene of Arabidopsis, NDH-dependent cyclic electron flow 5 (NDF5, At1g55370). Post-illumination increases in chlorophyll fluorescence were absent in ndf5 mutant plants, which indicated that NDF5 is essential for NDH activity. Sequence analysis did not reveal any known functional motifs in NDF5, but there was some homology in amino acid sequence between NDF5 and NDF2, a known NDH subunit. NDF5 and NDF2 homologs were present in higher plants, but not cyanobacteria. A single homolog, which had similarity to both NDF5 and NDF2, was identified in the moss Physcomitrella patens. Immunoblot analysis showed that NDF5 localizes to membrane fractions of chloroplasts. The stability of NdhH, a subunit of the NDH complex, as well as NDF5 and NDF2, was decreased in ndf5, ndf2 and double ndf2/ndf5 mutants, resulting in a loss of NDH activity in these mutants. These results indicated that both NDF5 and NDF2 have essential functions in the stabilization of the NDH complex. We propose that NDF5 and NDF2 were acquired by land plants during evolution, and that in higher plants both NDF5 and NDF2 are critical to regulate NDH activity and each other's protein stability, as well as the stability of additional NDH subunits.

Keywords: Arabidopsis; Cyclic electron flow; NAD(P)H dehydrogenase (NDH, EC 1.6.99.3)

Journal Article.  6419 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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