Sequence analysis and hormonal regulation of a dehydrin promoter from barley, Hordeum vulgare

Abstract

A dehydrin gene (dhn7) was isolated from a barley (Hordeum vulgare L. cv. Himalaya) genomic library. A 2138‐bp fragment of the gene was sequenced and the deduced amino acid sequence showed 99% identity with that of a previously identified cDNA, Dhn 1, which encodes one of a group of closely related proteins induced by dehydration stress. Transient expression assays in barley aleurone protoplasts defined regions of the dhn7 promoter that mediate abscisic acid (ABA) responsive transcription. A fragment (‐935 to +42) of the gene was found to confer concentration‐dependent ABA‐responsiveness measured by expression of a β‐glucuronidase (GUS) reporter gene. Analysis of a 5’deletion series of the promoter defined a region (‐285 to ‐233) that modulated the amplitude of the ABA‐response, whilst ABA‐responsiveness, per se, required a region (‐233 to ‐211) that included a conserved motif containing the G‐box‐like sequence TACGTGG. Gibberellic acid (GA3) antagonised ABA‐induced accumulation of dehydrin mRNA in aleurone cells, but did not antagonise ABA‐induced transcriptional activation as revealed by GUS activity. The antagonistic effect of GA3 on ABA‐induced dehydrin expression might therefore operate post‐transcriptionally.