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

A dehydrin gene ( dhn 7) 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 (GA 3 ) 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 GA 3 on ABA‐induced dehydrin expression might therefore operate post‐transcriptionally.