An Arabidopsis cDNA (Atmyb2) that contains a sequence that encodes a transcription factor, which is a homolog of MYB, was cloned from a cDNA library prepared from dehydrated Arabidopsis rosette plants. A gene (AtmybP) corresponding to the Atmyb2 cDNA was also cloned and its nucleotide sequence was determined. RNA gel blot analysis showed that the AtmybP mRNA was induced by dehydration and dísappeared upon rehydration. The Atmyb2 mRNA also accumulated upon salt stress and with the onset of treatment with abscisic acid. A Pglucuronidase reporter gene driven by the AtmybP promoter was induced by dehydration and salt stress in transgenic Arabidopsis plants. These observations indicate that AtmybP is responsive to dehydration at the transcriptional level. The putative protein (ATMYB2) encoded by AtmybP has 274 amino acids, a molecular m a s of 32 kD, and a putative DNA binding domain that shows considerable homology to plant MYB-related proteins, such as maize C1. A fusion protein that included ATMYBP was expressed in Escherichia coli, and it bound specifically to oligonucleotides that contained a consensus MYB recognition sequence (TAACTG), such as is found in the simian virus 40 enhancer and the maize bronze1 promoter. Binding was sequence specific, as indicated by a gel mobility shift experiment. These results suggest that a MYB-related transcription factor is involved in the regulation of genes that are responsive to water stress in Arabidopsis.