Enhanced Tolerance To Salt Stress Of Transgenic Rice Plants By Overexpressing A Halophilic Archaeon (Natrinema Sp.) Manganese Superoxide Dismutase

Soil salinity has been aggravated by agricultural practices such as irrigation and inapprooriate fertilization (Mahajan and Tuteja,2005). It has been a global problem. Salinity can lead to osmotic stress, ion toxicity, and secondary stresses such as oxidative damage and nutritious imbalance, which adversely affect the quantity and quality of the crop production. One of the most important mechanisms of high plant to cope with salt stresse is scavenging reactive oxygen species (ROS) efficiently to prevent salt-induced oxidative damage. Among ROS-scavenging enzymes, superoxide dismutase (SOD) plays a crucial role. In the antioxidating process, SOD. as the first defense line, converts superoxide radical(O2) into hydrogen peroxide (H2O2). Many studies have found a positive correlation between salt stress and the abundance of SOD in plants.In this study, the transgenic rice plants overexpressing manganese superoxide dismutase (MnSOD) exhibited enhanced salt tolerance. The gene of NaMnSOD from halophilic archaeon (Natrinema sp.) was successfully introduced into rice by Agrobacterium-mediated transformation and functionally expressed, confirmed by polymerase chain reaction (PCR) and SOD activity staining, respectively. Under100mM NaCl treatment, the transgenic plants grew better than the wild type plants. Moreover, the transgenic rice plants maintained higher photosynthesis rate, whereas lower relative ion leakage and malondialdehyde (MDA) content, indicating that the transgenic plants were more resistant to salt-induced oxidative stress. Furthermore, we observed a higher catalase (CAT) activity in transgenic plants under salt stress than that in wild type, suggesting that the introduced MnSOD improved salt tolerance of transgenic rice plants by elevating ROS eli minating efficiency. As expected, the contents of O2and H2O2of transgenic plants were significantly lower than that of wild type plants. These results suggested that SOD played a critical role in the ROS scavenging system and the overexpression of NaMnSOD can improve salt tolerance in rice.