title: Modification of reactive oxygen species scavenging capacity of chloroplasts through plastid transformation.
abstract: Reactive oxygen species (ROS), including superoxide anions, hydrogen peroxide and hydroxyl radicals are generated through normal biochemical processes, but their production is increased by abiotic stresses. The prospects for enhancing ROS scavenging, and hence stress tolerance, by direct gene expression in a vulnerable cell compartment, the chloroplast, have been explored in tobacco. Several plastid transformants were generated which contained either a Nicotiana mitochondrial superoxide dismutase (MnSOD) or an Escherichia coli glutathione reductase (gor) gene. MnSOD lines had a three-fold increase in MnSOD activity, but interestingly a five to nine-fold increase in total chloroplast SOD activity. Gor transgenic lines had up to 6 times higher GR activity and up to 8 times total glutathione levels compared to wild type tobacco. Photosynthetic capacity of transplastomic plants, as measured by chlorophyll content and variable fluorescence of PSII was equivalent to non-transformed plants. The response of these transplastomic lines to several applied stresses was examined. In a number of cases improved stress tolerance was observed. Examples include enhanced methyl viologen (Paraquat)-induced oxidative stress tolerance in Mn-superoxidase dismutase over-expressing plants, improved heavy metal tolerance in glutathione reductase expressing lines, and improved tolerance to UV-B radiation in both sets of plants.
authors.affiliation: Department of Biology, Midland College, Midland, TX 79705, USA.
authors.forename: Miranda
authors.initials: M
authors.lastname: Poage
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Le Martret
authors.forename: Marcel A K
authors.initials: MA
authors.lastname: Jansen
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Nugent
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Dix
mesh_terms: D001483:Base Sequence; D019470:Biolistics; D015139:Blotting, Southern; D002104:Cadmium / Q000494:pharmacology; D002736:Chloroplasts / Q000201:enzymology / Q000378:metabolism*; D017931:DNA Primers; D018525:Germination / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D005980:Glutathione Reductase / Q000235:genetics; D030821:Plants, Genetically Modified / Q000235:genetics; D018087:Plastids; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000235:genetics; D014466:Ultraviolet Rays
chemical_list: D017931:DNA Primers; D017382:Reactive Oxygen Species; D002104:Cadmium; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005978:Glutathione