Studies On Pea Catalase Gene Expression In Plant Chloroplasts And Stress-resistance Analysis

Drought has been one of the most important disaster threatening agriculture in the world. It affects the growth of plants ,reduces the yield sharply and exacerbates the global food crisis. Use the transgenic technology to culture new varieties is an effective method which can improve the plants' ability of drought-resistance. Under drought condition,plants often suffer from osmotic stress and oxidative stress. Betaine is one of the nontoxic and organic osmolytes which can accumulate rapidly in many plants under drought stress,it plays an important role in maintaining osmotic balance and protecting some important enzymes in plant cells. Catalase can remove H₂O₂ in most plants,especially under drought stress, it plays an important role in anti-oxidation. Catalase mainly locates in the peroxisome, not the chloroplast. But under the condition of drought stress, reactive oxidative species are produced mainly in chloroplast. The reactive oxidative species will injure the chloroplast seriously.We introduce the Tr-cat gene into tobacco overexpressing Badh,so the CAT can function in the chloroplast. Exogenous protein was over-expressed in tobacco. Betaine accumulation and CAT activity in transformed tobaccos were higher than that in control plants. And the ability of stress-tolerance in transformed tobaccos was higher than that in control plants. In this paper, we use the transgenic tobacco as the materials, study the stress-resistance mechanism of the plants, and provide the evidence that targeting protein locates in the chloroplast. The result is as follows:1. The chloroplast of transgenic plants was separated, and the result of Western blot confirmed that the production of Cat has been located in the chloroplast, and the targeting protein play a role in the chloroplast.2.Under different concentration PEG6ooo,the damages of PS II in transgenic tobaccos was lower than that in control plants, the activities of the CAT,POD were higher than that in control plants, and the content of MDA was lower than that in control plants. The results indicate the new genes had improved the ability of drought-tolerance in transformed tobaccos.3.Under different concentration NaCl, the damages of PS II in transgenic tobaccos was lower than that in control plants, the activities of the CAT was higher than that in control plants, and the content of MDA was lower than that in control plants. The results indicate that the new genes introduced into the tobaccos had improved the plants' ability of salt-tolerance. 4.Under different concentration paraquat, the activities of the CAT in transgenic tobaccos was higher than that in control plants and the damages of PS II in transgenic tobaccos was lower than that in control plants, the results indicated that the ability of anti-oxidation in transgenic tobaccos was higher than that in control tobaccos.