Significance of antioxidant enzymes in stress signaling in Withania sominifera (L.) Dunal

Abstract

Plant exposed to stress undergoes changes in their metabolism in order to adapt to the changes in their environment. The present study was conducted to reveal the role of antioxidant enzymes like superoxide dismutase and peroxidase during acetyl salicylic acid and sodium chloride salt (NaCl) signaling in Withania sominifera (L.) Dunal. using enzyme activity staining on acrylamide gels. The results showed that during acetyl salicylic acid signaling, superoxide dismutase (SOD) activity increased in 2nd and 4th hrs and decreased till 6th hrs and further increased up to 10th hrs. Similarly in peroxidase, a low enzyme activity was observed in 0 and 6th hrs while in 2nd, 4th, 8th and 10th hrs the expressions of three isozymes of peroxidases were observed. Activity by 6th hrs may result in increased accumulation of H2O2 resulting in oxidative burst. The decrease in, superoxide dismutase activity may be due to the feedback inhibition mechanism of the enzyme. During sodium chloride salt stress only, superoxide dismutase activity was localized since Peroxidase (POD) activity was negligible. In different sodium chloride salt (concentration from 1000 to 6000 ppm, the, superoxide dismutase activity was maximum increase during 5000 ppm treatment revealed by the presence of three bands. During time dependent sodium chloride salt treatment, the superoxide dismutase activity increased during 2nd to 8th hrs of treatment revealed by the presence of two bands. The result in the present study highlight a probable occurrence of oxidative burst in Withania sominifera (L.) during 4th and 6th hrs of stress signaling. Sometimes high amount of Hydrogen Peroxide accumulated and generating PCR/HR signals against plant pathogens to protect plant.