Plant productivity is markedly affected by drought stress. We reported that a cis-acting promoter element, dehydration-responsive element (DRE), plays an important role in regulating gene expression in response to drought stress in Arabidopsis. The DRE is also involved in low-temperature- and salt-responsive gene expression. The transcription factor DREB1A specifically interacts with the DRE and induces the expression of stress tolerance genes. Overexpression of the cDNA encoding DREBlA in transgenic Arabidopsis plants activated the expression of many of these stress tolerance genes under normal growing conditions and resulted in improved tolerance to drought, salt loading, and freezing. We prepared a cDNA microarray using full-length Arabidopsis cDNAs to identify the target stress tolerance genes of DREB1A. Twelve stress-inducible genes were identified as the target genes of DREBlA, and six of them were new. However, the use of the
strong constitutive 35S cauliflower mosaic virus (CaMV) promoter to drive the expression of DREB1A resulted in severe growth retardation under normal growing conditions. In contrast, the expression of DREBlA 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 the expression of the gene from the 35S CaMV promoter. As the DRE-related regulatory element is not limited to Arabidopsis, the DREBlA cDNA and the rd29A promoter may be useful to improve the stress tolerance of agriculturally important crops by gene transfer.