Overexpression of the Cotton CBF2 Gene Enhances Salt and Drought Tolerance in Arabidopsis thaliana

CBF/DREB proteins are transcription factors in plants, which play important biological functions in cold, drought, and salt stress resistance. In this study, a CBF/DREB gene, GhCBF2, was cloned from Gossypium hirsutum L., coding a protein consisting of 216 amino acids. Sequence analysis indicated that GhCBF2 contained a typical AP2 conservative domain structure, much like the CBF proteins in other plant species. The transcript of the GhCBF2 gene in cotton seedlings was upregulated following exposure to drought and salt stress. Subcellular localization of proteins showed that the GhCBF2-GFP fusion protein was localized to the nucleus. To study the function of the GhCBF2 gene in drought and salt stress resistance, it was inserted into pMD to construct a GhCBF2-overexpression vector under the control of CaMV 35S promoter. The construct was introduced into Arabidopsis thaliana by the floral dip method. Analysis of resistance to drought and salt stress showed that the survival rate of transgenic A. thaliana plants was improved remarkably compared to that of the wildtype (WT) plants. The proline and soluble sugar contents in the transgenic plants were also higher than those in the WT plants. These results show that GhCBF2 can enhance transgenic plant tolerance to drought and salt stress. We selected several stress related genes, including COR15A, RD29A, and ERD6, and examined their expression by quantitative RT-PCR in both transgenic and WT plants. Remarkably, the expressions of these marker genes in GhCBF2-overexpressed transgenic plants were substantially higher than those in WT plants, indicating that the GhCBF2 gene is involved in the regulation of drought and salt related genes.