Improving plant drought, salt and freezing tolerance by gene transfer of a single stress-inducible transcription factor.

Plant productivity is greatly affected by environmental stresses such as drought, salt loading and freezing. We reported that a cis-acting promoter element, the dehydration response element (DRE), plays an important role in regulating gene expression in response to these stresses in Arabidopsis. The transcription factor DREB1A specifically interacts with the DRE and induces expression of stress tolerance genes. We show here that overexpression of the cDNA encoding DREB1A in transgenic Arabidopsis plants activated the expression of many of theses stress tolerance genes under normal growing conditions and resulted in improved tolerance to drought, salt loading and freezing. However, use of the strong constitutive 35S cauliflower mosaic virus (CaMV) promoter to drive expression of DREB1A also resulted in severe growth retardation under normal growing conditions. In contrast, expression of DREB1A from the stress-inducible rd29A promoter gave rise to minimal effects on plant growth while providing an even greater tolerance to stress conditions than did expression of the gene from the CaMV promoter. As the DRE-related regulatory element is not limited to Arabidopsis the DREB1A cDNA and the rd29A promoter may be useful for improving the stress tolerance of agriculturally important crops by gene transfer.