Overexpression Of Cu/Zn-SOD Gene From Chaetomium Thermophilum Enhanced Resistance Of Transgenic Rice Against To Three Major Diseases

Rice (Oryza sativa) is one of the most important crops in China. Bacterial leaf streak caused by Xanthomonas oryzae pv.oryzicola (Xoc) and bacterial blight caused by Xanthomonas oryzae pv. oryzae(Xoo) are two most serious bacterial dieases in rice. Rice sheath blight caused by Rhizoctonia solani Kiihn expands quickly in recent years and trends to surpass rice blast in terms of the incidence area to become the most severe one in rice. However, there is no report that single defense-related gene can be resistant to the three diseases simultaneously.The superoxide dismutases (SOD, EC1.15.1.1) play critical roles in the defense against oxidative stresses. Many studies have shown that improving SOD activity could increase the adaptation and tolerance to many environmental stresses for plants. In this study we focused on thermal stability gene encoded a Cu/Zn-SOD (CtSOD for short, GeneBank: DQ493760.1)from Chaetomium thermophilum. Previously studies indicated that the expression of CtSOD gene can enhance their resistance to harmful environment in Paster pastoris. But there is no relevant reports in plants yet. The CtSOD gene was inserted into PU1301plasmid and then was introduced into rice by Agrobacteriwn-mediated transformation. The total of10transgenic individuals were obtained. Eight out of ten individuals were identified as positive lines after detection with genomic DNA PCR and GUS staining. Further more, SOD activity of positive transgenic plants was significantly improved from38%to73%compared with the wild-type plants.We also analyzed the resistance of transgenic plants to rice bacterial blight. T0and T1generation of transgenic plants were reduced significantly with lesion area. And the result was negatively correlated with the increased activity of SOD. Also T1generation of transgenic plants showed that the growth of pathogens was obviously inhibited in positive lines. Similar as resistance to Xoo, To generation of transgenic lines displayed shortened lesion length varied from45%to60%compared to wild-type plants after inoculation with Xoc. It was indicated that overexpression of CtSOD resulted to enhance resistance to bacterial leaf streak. The total of4lines had been detected to against sheath blight fungal disease at T2generation. The results was suggested that overexpression of CtSOD showed enhanced resistance to sheath blight.In general, we have introduced an exogenous CtCu/Zn-SOD gene into rice variety Zhonghua11. The SOD activity and resistance abilities to three major rice dieases were all significantly improved in transgenic rice lines. The results demonstrated that the overexpression of exogenous CtCu/Zn-SOD gene can increase the ability of rice to withstand biotic stress and indicated the transgenic lines can be important in agricultural production for its broader resistance spectrum to different rice pothogens.