HORMONE RESPONSE COMPLEX IN A NOVEL ABSCISIC-ACID AND CYCLOHEXIMIDE-INDUCIBLE BARLEY GENE

The phytohormone, abscisic acid (ABA), plays a variety of roles during , seed development and, in the plant's response to environmental stres ses. To study the molecular action of ABA, we have isolated a single c opy ABA-induced gene, HVA22, which is mapped to barley chromosome 1. T he HVA22 gene can be induced by either ABA or the protein synthesis in hibitor, cycloheximide, and addition of both inducers to barley aleuro ne layers has a synergistic effect on the expression of this gene. Seq uence comparison indicates that the HVA22 gene product is highly homol ogous to the product of human DP1 gene, which is likely to contribute to colorectal tumorigenesis. The hormonal regulation of HVA22 expressi on has been studied, and there appear to be at least three elements, t wo located in the promoter and one in the first intron, which are esse ntial for the high level of ABA induction of HVA22 expression. Among t he promoter elements is a homolog of ABA response element, which has b een shown to be important in the expression of other ABA-induced genes in plants. We suggest that the barley HVA22 gene product is likely a regulatory protein, and the ABA induction of this gene requires the ac tion of a complex set of hormone response elements.