title: Regulation of NAD(P)H dehydrogenase-dependent cyclic electron transport around PSI by NaHSO₃ at low concentrations in tobacco chloroplasts.
abstract: Although bisulfite at low concentrations (L-NaHSO₃) has been found to increase the cyclic electron transport around PSI (CET), its regulative mechanism remains unknown. In this work, the role of L-NaHSO₃ (0.1-500 μM) in NAD(P)H dehydrogenase-dependent CET (the NDH pathway) was investigated. After treatment of tobacco leaves with L-NaHSO₃, the NDH pathway, as reflected by a transient post-illumination increase in Chl fluorescence, the dark reduction of P700+ after far-red light and the amount of NDH, was increased after the light-dark-light transition, but was slightly lowered under continuous light. Meanwhile, the linear electron transport (LET) was accelerated by L-NaHSO₃ under both the light regimes. Experiments in thylakoids further demonstrated that both LET, monitored by light-dependent oxygen uptake, and CET, as determined from the NADPH-dependent oxygen uptake and dark reduction of P700+, were enhanced by L-NaHSO₃ and the enhancements were abolished by superoxide dismutase. Furthermore, L-NaHSO₃-induced CET was partially impaired in thylakoids of the ΔndhCKJ mutant, while L-NaHSO₃-induced LET was not affected. Based on these results, we propose that the photooxidation of L-NaHSO₃ initiated by superoxide anions in PSI regulates NDH pathway to maintain efficient photosynthesis.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, PR China.
authors.forename: Yanxia
authors.initials: Y
authors.lastname: Wu
authors.forename: Fangfang
authors.initials: F
authors.lastname: Zheng
authors.forename: Weimin
authors.initials: W
authors.lastname: Ma
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Han
authors.forename: Qun
authors.initials: Q
authors.lastname: Gu
authors.forename: Yunkang
authors.initials: Y
authors.lastname: Shen
authors.forename: Hualing
authors.initials: H
authors.lastname: Mi
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects* / Q000201:enzymology* / Q000528:radiation effects; D004579:Electron Transport / Q000187:drug effects / Q000528:radiation effects; D004583:Electrons; D005453:Fluorescence; D015151:Immunoblotting; D008954:Models, Biological; D009249:NADP / Q000378:metabolism; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D010100:Oxygen / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D010971:Plastoquinone / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D013447:Sulfites / Q000494:pharmacology*; D020524:Thylakoids / Q000187:drug effects / Q000378:metabolism; D014026:Nicotiana / Q000187:drug effects* / Q000201:enzymology* / Q000528:radiation effects
chemical_list: D045331:Photosystem I Protein Complex; D021122:Protein Subunits; D013447:Sulfites; D002734:Chlorophyll; D009249:NADP; D009252:NADPH Dehydrogenase; D010971:Plastoquinone; D010100:Oxygen; C009279:sodium bisulfite