title: Cyclic electron flow around photosystem I via chloroplast NAD(P)H dehydrogenase (NDH) complex performs a significant physiological role during photosynthesis and plant growth at low temperature in rice.
abstract: The role of NAD(P)H dehydrogenase (NDH)-dependent cyclic electron flow around photosystem I in photosynthetic regulation and plant growth at several temperatures was examined in rice (Oryza sativa) that is defective in CHLORORESPIRATORY REDUCTION 6 (CRR6), which is required for accumulation of sub-complex A of the chloroplast NDH complex (crr6). NdhK was not detected by Western blot analysis in crr6 mutants, resulting in lack of a transient post-illumination increase in chlorophyll fluorescence, and confirming that crr6 mutants lack NDH activity. When plants were grown at 28 or 35°C, all examined photosynthetic parameters, including the CO(2) assimilation rate and the electron transport rate around photosystems I and II, at each growth temperature at light intensities above growth light (i.e. 800 μmol photons m(-2) sec(-1)), were similar between crr6 mutants and control plants. However, when plants were grown at 20°C, all the examined photosynthetic parameters were significantly lower in crr6 mutants than control plants, and this effect on photosynthesis caused a corresponding reduction in plant biomass. The F(v)/F(m) ratio was only slightly lower in crr6 mutants than in control plants after short-term strong light treatment at 20°C. However, after long-term acclimation to the low temperature, impairment of cyclic electron flow suppressed non-photochemical quenching and promoted reduction of the plastoquinone pool in crr6 mutants. Taken together, our experiments show that NDH-dependent cyclic electron flow plays a significant physiological role in rice during photosynthesis and plant growth at low temperature.
authors.affiliation: Department of Applied Plant Science, Graduate School of Agricultural Science, Tohoku University, Aoba-ku, Sendai 981-8555, Japan. wataru.yamori@biochem.tohoku.ac.jp
authors.forename: Wataru
authors.initials: W
authors.lastname: Yamori
authors.forename: Naoki
authors.initials: N
authors.lastname: Sakata
authors.forename: Yuji
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
authors.forename: Amane
authors.initials: A
authors.lastname: Makino
mesh_terms: D003080:Cold Temperature; D004579:Electron Transport / Q000502:physiology*; D017343:Genes, Plant; D009154:Mutation; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000502:physiology*; D012275:Oryza / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology*; D045331:Photosystem I Protein Complex / Q000378:metabolism*
chemical_list: D045331:Photosystem I Protein Complex; D009252:NADPH Dehydrogenase