Enhanced tolerance to salt stress and water deficit by overexpressing superoxide dismutase in tobacco ( Nicotiana tabacum) chloroplasts

A chimeric gene consisting of the coding sequence for cytosolic Cu/Zn-superoxide dismutases (SOD) from Oryza sativa fused to the chloroplast transit sequence from Arabidopsis thaliana glutathione reductase was used for generating transgenic tobacco plants. This construct was cloned into appropriate binary vector and mobilized into Agrobacterium tumefaciens C58C2. Tobacco leaf discs were infected with Agrobacterium and cultured on kanamycin selective medium. The integration and expression of Cu/Zn-SOD in tobacco genome was confirmed by Southern dot blot hybridization and SOD activity staining, respectively. Several transgenic lines were obtained and screened for SOD activity. The transgenic lines showed enhanced tolerance to the active oxygen-generating paraquat and sodium sulfite. Similarly, when net photosynthesis was measured, the first generation of the transgenic lines showed enhanced tolerance to salt, water, and PEG stresses, over the wild type. These results suggested that the overexpressed Cu/Zn-SOD enhances the chloroplast antioxidant system.