title: Tobacco chloroplast transformants expressing genes encoding dehydroascorbate reductase, glutathione reductase, and glutathione-S-transferase, exhibit altered anti-oxidant metabolism and improved abiotic stress tolerance.
abstract: One approach to understanding the Reactive Oxygen Species (ROS)-scavenging systems in plant stress tolerance is to manipulate the levels of antioxidant enzyme activities. In this study, we expressed in the chloroplast three such enzymes: dehydroascorbate reductase (DHAR), glutathione-S-transferase (GST) and glutathione reductase (GR). Homoplasmic chloroplast transformants containing either DHAR or GST, or a combination of DHAR:GR and GST:GR were generated and confirmed by molecular analysis. They exhibited the predicted changes in enzyme activities, and levels or redox state of ascorbate and glutathione. Progeny of these plants were then subjected to environmental stresses including methyl viologen (MV)-induced oxidative stress, salt, cold and heavy metal stresses. Overexpression of these different enzymes enhanced salt and cold tolerance. The simultaneous expression of DHAR:GR and GST:GR conferred MV tolerance while expression of either transgene on its own didn't. This study provides evidence that increasing part of the antioxidant pathway within the chloroplast enhances the plant's ability to tolerate abiotic stress.
authors: Biology Department, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland.
authors: Bénédicte
authors: B
authors: Le Martret
authors: Miranda
authors: M
authors: Poage
authors: Karen
authors: K
authors: Shiel
authors: Gregory D
authors: GD
authors: Nugent
authors: Philip J
authors: PJ
authors: Dix
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D058639:Cold-Shock Response; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000235:genetics* / Q000378:metabolism; D005982:Glutathione Transferase / Q000235:genetics* / Q000378:metabolism; D019216:Metals, Heavy / Q000633:toxicity; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010269:Paraquat / Q000633:toxicity; D018515:Plant Leaves / Q000187:drug effects; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D055049:Salt Tolerance; D013312:Stress, Physiological / Q000235:genetics; D014026:Nicotiana / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*
chemical_list: D000975:Antioxidants; D019216:Metals, Heavy; D017382:Reactive Oxygen Species; D010088:Oxidoreductases; D005980:Glutathione Reductase; C020666:glutathione dehydrogenase (ascorbate); D005982:Glutathione Transferase; D005978:Glutathione; D010269:Paraquat; D001205:Ascorbic Acid