Structure and expression of the Arabidopsis thaliana homeobox gene Athb-12

We have isolated the Arabidopsis thaliana homeobox gene Athb-12, determined its structure and activation domain, demonstrated that its promoter is ind ucible in response to abscisic acid (ABA) treatment, and characterized the cellular distribution of its transcripts. The single intron of the gene int errupted the leucine-zipper domain region. The 5 ' regulatory region of Ath b-12 can drive beta -glucuronidase (GUS) expression in tobacco transgenic p lants. Athb-12 gene expression was further examined using in situ hybridiza tion to determine the cellular distribution of Athb-12 transcripts during A BA induction. A complex pattern of Athb-12 expression was observed, often a ssociated with regions of developing vascular tissues. Analysis of chimeras constructed from Athb-12 and the DNA-binding domain of the Saccharomyces c erevisiae transcription factor GAL4 revealed that the activation domain of Athb-12 lies in the C-terminal region (amino acids 180 to 235). Taken toget her, our data suggest that Athb-12 is a transcriptional activator important in regulating certain developmental processes as well as in the plant's re sponse to water stress involving ABA-mediated gene expression. (C) 2001 Aca demic Press.