title: The function of chloroplastic NAD(P)H dehydrogenase in tobacco during chilling stress under low irradiance.
abstract: The function of chloroplastic NAD(P)H dehydrogenase (NDH) was examined by comparing a tobacco transformant (DeltandhB) in which the ndhB gene had been disrupted with its wild type, upon exposure to chilling temperature (4 degrees C) under low irradiance (100 micro mol m(-2) s(-1) PFD). During the chilling stress, the maximum photochemical efficiency of PSII (F(v)/F(m)) decreased markedly in both the wild type and DeltandhB. However, both F(v)/F(m) and P700(+), as well as the PSII-driven electron transport rate (ETR), in DeltandhB were lower than that in the wild type, implying that NDH-dependent cyclic electron flow around PSI functioned to protect the photosynthetic apparatus from chilling stress under low irradiance. Under the stress, non-photochemical quenching (NPQ), particularly the fast relaxing NPQ component (qf) and the de-epoxidized ratio of the xanthophyll cycle pigments, (A+Z)/(V+A+Z), were distinguishable in DeltandhB from those in the wild type. The lower NPQ in DeltandhB might be related to an inefficient proton gradient across thylakoid membranes (DeltapH) because of lacking an NDH-dependent cyclic electron flow around PSI at chilling temperature under low irradiance.
authors.affiliation: College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong, 271018, P.R. China. qwmeng@sdau.edu
authors.forename: Xin-Guo
authors.initials: XG
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Duan
authors.forename: Qing-Wei
authors.initials: QW
authors.lastname: Meng
authors.forename: Qi
authors.initials: Q
authors.lastname: Zou
authors.forename: Shi-Jie
authors.initials: SJ
authors.lastname: Zhao
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D003080:Cold Temperature; D004579:Electron Transport / Q000235:genetics / Q000528:radiation effects; D008027:Light; D009154:Mutation / Q000235:genetics; D009252:NADPH Dehydrogenase / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D024341:Xanthophylls / Q000235:genetics / Q000528:radiation effects
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D024341:Xanthophylls; D002734:Chlorophyll; C001785:chlorophyll P 700; D009252:NADPH Dehydrogenase