1. Lecture14 Stress senescence tolerant plants

2. Development of oxidative stress tolerant plants Under oxidative stress the enzyme superoxide dismutase detoxifies super oxide anion to hydrogen peroxide and then to water and oxygen Under oxidative stress the enzyme superoxide dismutase detoxifies super oxide anion to hydrogen peroxide and then to water and oxygen

3. Development of oxidative stress tolerant plants tobacco plants transformed with a superoxide dismutase gene tobacco plants transformed with a superoxide dismutase gene under the control of the 35S promoter from cauliflower mosaic virus under the control of the 35S promoter from cauliflower mosaic virus reduced oxygen radical damage under stress conditions compared with control plants reduced oxygen radical damage under stress conditions compared with control plants

4. Oxidative stress tolerant plants Stress reduced if the level of oxidized glutathione within a plant is increased Stress reduced if the level of oxidized glutathione within a plant is increased a tobacco cDNA encoding an enzyme with both glutathione S-transferase and glutathione peroxidase activity was isolated a tobacco cDNA encoding an enzyme with both glutathione S-transferase and glutathione peroxidase activity was isolated Glutathione peroxidase catalyzes the conversion of glutathione (GSH) to oxidized glutathione (GSSG) by reacting with organic peroxides and reducing them to organic alcohols (Fig.2) Glutathione peroxidase catalyzes the conversion of glutathione (GSH) to oxidized glutathione (GSSG) by reacting with organic peroxides and reducing them to organic alcohols (Fig.2)

5. Oxidation of GSH to GSSH and simultaneous reduction of organic peroxide to an organic alcohol, catalyzed by glutathione peroxidase

6. Oxidative stress tolerant plants Transgenic tobacco plants that express glutathione peroxidase were created Transgenic tobacco plants that express glutathione peroxidase were created using the isolated cDNA under the control of the 35S promoter using the isolated cDNA under the control of the 35S promoter the construct introduced into plants with a binary Ti plasmid system the construct introduced into plants with a binary Ti plasmid system transformed plant had approximately twice the level of enzyme activity found in non transformed plants transformed plant had approximately twice the level of enzyme activity found in non transformed plants