Plant productivity is greatly affected by environmental stresses such as drought, salt loading and freezing. Recently, a major transcription system that controls gene expression in response to dehydration and low temperature has been identified. The system includes the DRE/CRT cis-acting element and its DNA-binding proteins, DREBs/CBFs, which have an AP2 domain. DREBs/CBFs contain two subclasses, DREB1/CBF and DREB2, which are induced by cold and dehydration, respectively, and control the expression of various genes involved in stress tolerance. Overexpression of the cDNA encoding DREB1/CBF in transgenic Arabidopsis activated the expression of many of these stress tolerance genes and resulted in improved tolerance to drought, saltloading and freezing. Overexpression of Arabidopsis DREB1/CBF genes in several kinds of crop plants induced expression of orthologs of Arabidopsis DREB-targeted genes and increased the freezing tolerance of transgenic plants. These observations suggest that the DRE/DREB regulon can be used to improve the tolerance of various kinds of agriculturally important crop plants to drought, high-salt, and freezing stresses by gene transfer.
