Increased tolerance to photooxidative stress by overexpression of mitochondrial superoxide dismutase in transgenic tobacco

Abstract

Under abiotic stress conditions, plants suffer from oxidative damage caused by increased generation of reactive oxygen species (ROS). Although chloroplasts are the main source of ROS generation in plant cells, changes in ROS level in mitochondria affect plant stress response. In this study, we investigated whether overexpression of mitochondrial manganese superoxide dismutase (Mn-SOD) can enhance tolerance to photooxidative stress. We produced transgenic tobacco plants overexpressing rice Mn-SOD under the control of cauliflower mosaic virus 35S promoter, and assessed the stress tolerance of those plants. The transgenic lines showed higher total SOD activity by 2.8 to 5.2 fold than wild type plants. Chlorophyll fluorescence measurement revealed that the stress-induced inhibition of photosystem II was alleviated under high light, chilling and heat stresses in the transgenic lines. This result indicates that the Mn-SOD contributes to the defense against photooxidative damages in chloroplasts under these stress conditions.