title: Composition and physiological function of the chloroplast NADH dehydrogenase-like complex in Marchantia polymorpha.
abstract: The chloroplast NADH dehydrogenase-like (NDH) complex mediates cyclic electron transport and chloro-respiration and consists of five sub-omplexes, which in angiosperms further associate with photosystem I (PSI) to form a super-complex. In Marchantia polymorpha, 11 plastid-encoded subunits and all the nuclear-encoded subunits of the A, B, membrane and ferredoxin-binding sub-complexes are conserved. However, it is unlikely that the genome of this liverwort encodes Lhca5 and Lhca6, both of which mediate NDH-PSI super-complex formation. It is also unlikely that the subunits of the lumen sub-complex, PnsL1-L4, are encoded by the genome. Consistent with this in silico prediction, the results of blue-native gel electrophoresis showed that NDH subunits were detected in a protein complex with lower molecular mass in Marchantia than the NDH-PSI super-complex in Arabidopsis. Using the plastid transformation technique, we knocked out the ndhB gene in Marchantia. Although the wild-type genome copies were completely segregated out, the ΔndhB lines grew like the wild-type photoautotrophically. A post-illumination transient increase in chlorophyll fluorescence, which reflects NDH activity in vivo in angiosperms, was absent in the thalli of the ΔndhB lines. In ruptured chloroplasts, antimycin A-insensitive, and ferredoxin-dependent plastoquinone reduction was impaired, suggesting that chloroplast NDH mediates similar electron transport in Marchantia and Arabidopsis, despite its possible difference in structure. As in angiosperms, linear electron transport was not strongly affected in the ΔndhB lines. However, the plastoquinone pool was slightly more reduced at low light intensity, suggesting that chloroplast NDH functions in redox balancing of the inter system, especially under low light conditions.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan CREST, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Ueda
authors.forename: Tetsuki
authors.initials: T
authors.lastname: Kuniyoshi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Sugimoto
authors.forename: Kimitsune
authors.initials: K
authors.lastname: Ishizaki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kohchi
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
mesh_terms: D000968:Antimycin A / Q000494:pharmacology; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D002736:Chloroplasts / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D004579:Electron Transport; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D004789:Enzyme Activation; D005453:Fluorescence; D055786:Gene Knockout Techniques; D061125:Genes, Chloroplast; D018745:Genome, Plant; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D047008:Marchantia / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D009245:NADH Dehydrogenase / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D010084:Oxidation-Reduction; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D010971:Plastoquinone / Q000378:metabolism; D060431:Thylakoid Membrane Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D060431:Thylakoid Membrane Proteins; D000968:Antimycin A; D009245:NADH Dehydrogenase; D010971:Plastoquinone