Studies On Transforming Tobacco By Relevant Gene Of Drought Resistance

Crop output is influenced by many kinds of factors, but drought occupies the first place among a great deal of factors, its extent of injury is equivalent to sum of others . The plant suffers from osmotic stress and oxidative stress in drought condition, so the way to improve the plant's drought-resistance lies in improving the plant's ability of osmotic adjustment and anti-oxidation. Under the condition of drought stress, plant accumulates many kinds of osmotic adjustment substance in the body to keep the osmotic balance. Among of them, the betaine is important in regulating the osmotic balance of the plant. In the higher plant, betaine is synthesized by the choline monooxygenase (CMO ) and betaine aldehyde dehydrogenase (BADH ). So transformation of Badh into plant and excessive expression in the plant will be important to improve the plant's drought-resistance ability. Catalase (CAT ),is regarded as a key enzyme in the anti-oxidation system in the plant, who can removes H₂O₂ produced in plants. CAT mainly locates in the peroxisome, not the chloroplast. But under the condition of drought stress, the chloroplast is the main position producing reactive oxidative species (ROS).The accumulation of ROS will seriously injure the chloroplast. So transformation of CAT into chloroplast is important to improve the plant's drought-resistance ability.In this experiment, the Tr-cat gene is transferred into tobacco overexpressing Badh mediated by the Agrobacterium tumifaciens. So the CAT can function in the chloroplast. Transformants were selected on the medium containing hygromycin(50 mg/L), about 30 trans-Cat lines and 30 trans-Cat, Badh lines were alive and used for further molecular and physiological determination. And then the tobacco was confirmed by PCR, RT-PCR and Wesrtern blotting. The result indicated that the Cat had been intergrated into tobacco genome, and expressed normally.The transgenic tobacco overexpressing Cat has improved drought-resistance andanti-oxidation ability.The tansformants and wild tobaccos were treated with 2O%PEG6ooo and paraquat with different concentrations, the result is as follows:1, Treated with 20% PEG6ooo-In the transformants ,the damages of cytoplasma membrane> chlorophyll and PS II are all lower than in wild tobacco.The results indicate the genes Badh and Cat overexpressing in tobacco improved its drought-resistance ability. In addition, the transgenic tobacco overexpressing both Badh and Cat showed higher drought-resistance ability than the trans-Cat and trans-Badh ones.2, Treated with different concentration paraquat.The result indicated that the genes Badh and Cat transferred into tobacco improved the transformants' anti-oxidation ability. Furthermore, the transgenic tobacco overexpressing both Badh and Cat showed higher anti-oxidation ability than the trans-Caf and trans- Badh ones.Above all, results of different tests indicated that the genes Badh and Cat transferred into tobacco has improved the transformants' abilities of drought resistance and anti-oxidation. In addition, the result indicated the irans-Badh and Cat tobacco improved its abilities of drought-resistance and anti-oxidation more effectively.