In order to verify the transcription factor CBF2 gene can be induced to express in plant and improve the plant salt resistance, they were cloned from the Arabidopsis thaliana by PCR according to CBF2 gene sequence published on GenBank. The plant expression vector (pBI-rd29A-CBF2) with CBF2 gene was constructed. The CBF2 gene was transformed into soybean plants via Agrobacterium-mediated transformation. It approved that the CBF2 gene had been transformed and integrated into the genome of soybean by PCR and Southern blot. Through the physiological test of salt resistance, the relative electric conductivity of the transformed plants plasma membrane and the control were 36.84% and 59.35% respectively under salt stress. The content of chlorophyll of the transformed plants was 2.41 times as much as that of the control. The content of proline of the transformed plants was 2.49 times as much as that of the control. It showed that the CBF2 gene was induced to express in soybean plants. And it also indicated that the expression of the CBF2 gene increased the salt stress tolerance of the transgenic soybean plants. The results proved the CBF2 gene were functional gene.

The osmotic stress and ion toxicity caused by high salt is one of the major abiotic stress factors that affect the crop growth and development. Na+/H+ antiporter is the key factor in the salt-stress tolerance in organism. It can maintain normal growth and metabolism of organism under high salt stress. PCR was per- formed to clone a plasma membrane Na+/H+ antiporter gene nhaA from Pseudomonas stutzeri, and the plant expression vector pBI121-nhaA was constructed. NhaA gene was trans- formed into soybean growing point via Agrobacterium- mediated transformation. PCR, Southern blot analysis showed that nhaA gene had been integrated into the soybean genome. Salt resistance analysis showed that the relative electronic conductivity of the transformed plants plasma membrane was signify- cantly lower than that of the control under salt stress. While the content of chlorophyll and proline in the transformed plants were significantly higher than that in the controls. The expression of nhaA gene increased the salt stress tolerance of the transgenic soybean and provided excellent candidate genes for improving salt tolerance of crops.