title: Enhanced sensitivity to oxidative stress in transgenic tobacco plants with decreased glutathione reductase activity leads to a decrease in ascorbate pool and ascorbate redox state.
abstract: To investigate the possible mechanisms of glutathione reductase (GR) in protecting against oxidative stress, we obtained transgenic tobacco (Nicotiana tabacum) plants with 30-70% decreased GR activity by using a gene encoding tobacco chloroplastic GR for the RNAi construct. We investigated the responses of wild type and transgenic plants to oxidative stress induced by application of methyl viologen in vivo. Analyses of CO(2) assimilation, maximal efficiency of photosystem II photochemistry, leaf bleaching, and oxidative damage to lipids demonstrated that transgenic plants exhibited enhanced sensitivity to oxidative stress. Under oxidative stress, there was a greater decrease in reduced to oxidized glutathione ratio but a greater increase in reduced glutathione in transgenic plants than in wild type plants. In addition, transgenic plants showed a greater decrease in reduced ascorbate and reduced to oxidized ascorbate ratio than wild type plants. However, there were neither differences in the levels of NADP and NADPH and in the total foliar activities of monodehydroascorbate reductase and dehydroascorbate reductase between wild type and transgenic plant. MV treatment induced an increase in the activities of GR, ascorbate peroxidase, superoxide dismutase, and catalase. Furthermore, accumulation of H(2)O(2) in chloroplasts was observed in transgenic plants but not in wild type plants. Our results suggest that capacity for regeneration of glutathione by GR plays an important role in protecting against oxidative stress by maintaining ascorbate pool and ascorbate redox state.
authors.affiliation: Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China.
authors.forename: Shunhua
authors.initials: S
authors.lastname: Ding
authors.forename: Qingtao
authors.initials: Q
authors.lastname: Lu
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Zhipan
authors.initials: Z
authors.lastname: Yang
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Wen
authors.forename: Lixin
authors.initials: L
authors.lastname: Zhang
authors.forename: Congming
authors.initials: C
authors.lastname: Lu
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005980:Glutathione Reductase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D050356:Lipid Metabolism / Q000187:drug effects; D008315:Malondialdehyde / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010269:Paraquat / Q000494:pharmacology; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013482:Superoxide Dismutase / Q000378:metabolism; D014026:Nicotiana / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*
chemical_list: D008315:Malondialdehyde; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D010269:Paraquat; D001205:Ascorbic Acid