Journal Article

The Function of Chloroplastic NAD(P)H Dehydrogenase in Tobacco during Chilling Stress under Low Irradiance

Xin-Guo Li, Wei Duan, Qing-Wei Meng, Qi Zou and Shi-Jie Zhao

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 1, pages 103-108
Published in print January 2004 | ISSN: 0032-0781
Published online January 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch011
The Function of Chloroplastic NAD(P)H Dehydrogenase in Tobacco during Chilling Stress under Low Irradiance

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The function of chloroplastic NAD(P)H dehydrogenase (NDH) was examined by comparing a tobacco transformant (ΔndhB) in which the ndhB gene had been disrupted with its wild type, upon exposure to chilling temperature (4°C) under low irradiance (100 µmol m–2 s–1 PFD). During the chilling stress, the maximum photochemical efficiency of PSII (Fv/Fm) decreased markedly in both the wild type and ΔndhB. However, both Fv/Fm and P700+, as well as the PSII-driven electron transport rate (ETR), in ΔndhB 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 ΔndhB from those in the wild type. The lower NPQ in ΔndhB might be related to an inefficient proton gradient across thylakoid membranes (ΔpH) because of lacking an NDH-dependent cyclic electron flow around PSI at chilling temperature under low irradiance.

Keywords: Keywords: Chilling stress — Cyclic electron flow — NAD(P)H dehydrogenase (NDH, EC 1.6.99.3) — Photoinhibition — The xanthophyll cycle — Tobacco.; Abbreviations: A, antheraxanthin; ETR, in vivo PSII-driven electron transport rate; Fm, maximal fluorescence with all PSII reaction centers closed in the dark-adapted state; Fv/Fm, maximal fluorescence efficiency of PSII; Fm′, maximal fluorescence of PSII in light-adapted state; Fs, steady-state fluorescence in light; Fv, variable fluorescence; Fo, original fluorescence; FQR, ferredoxin quinone reductase; MV, methyl viologen; NDH, NAD(P)H dehydrogenase; NPQ, non-photochemical quenching; P700, reaction center chlorophyll of PSI; PFD, photon flux density; PQ, plastoquinone; PSI, photosystem I; PSII, photosystem II; QA, the primary stable quinone electron acceptor of PSII; qf, fast relaxing non-photochemical quenching; qm, middle relaxing non-photochemical quenching; qs, slowly relaxing non-photochemical quenching; qP, photochemical quenching; V, violaxanthin; Z, zeaxanthin.

Journal Article.  4566 words.  Illustrated.

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

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