SEQUENCE-ANALYSIS AND HORMONAL-REGULATION OF A DEHYDRIN PROMOTER FROMBARLEY, HORDEUM-VULGARE

A dehydrin gene (dhn7) was isolated from a barley (Hordeum vulgare L. cv. Himalaya) genomic library. A 2138-bp fragment of the gene was sequ enced and the deduced amino acid sequence showed 99% identity with tha t of a previously identified cDNA, Dhn1, which encodes one of a group of closely related proteins induced by dehydration stress. Transient e xpression assays in barley aleurone protoplasts defined regions of the dhn7 promoter that mediate abscisic acid (ABA) responsive transcripti on. A fragment (-935 to +42) of the gene was found to confer concentra tion-dependent ABA-responsiveness measured by expression of a beta-glu curonidase (GUS) reporter gene. Analysis of a 5' deletion series of th e promoter defined a region (-285 to -233) that modulated the amplitud e of the ABA-response, whilst ABA-responsiveness, per se, required a r egion (-233 to -211) that included a conserved motif containing the G- box-like sequence TACGTGG. Gibberellic acid (GA(3)) antagonised ABA-in duced accumulation of dehydrin mRNA in aleurone cells, but did not ant agonise ABA-induced transcriptional activation as revealed by GUS acti vity. The antagonistic effect of GA(3) on ABA-induced dehydrin express ion might therefore operate post-transcriptionally.