Molecular analysis of the barley (Hordeum vulgare L.) gene encoding the protein kinase PKABA1 capable of suppressing gibberellin action in aleurone layers

Abstract.

Abscisic acid (ABA) induces the expression of a gene encoding a protein kinase, PKABA1, in wheat (Triticum aestivum L.). Transient expression of the cDNA encoding this kinase suppresses the gibberellin (GA)-induced expression of α-amylase genes in barley (Hordeum vulgare L.) aleurone layers. We have cloned the cDNA and genomic sequences for the barley PKABA1 (HvPKABA1) to further study its role in regulating the GA-inducible gene expression in barley seeds. The amino acid sequence deduced from the cDNA shows 97% identity with that of wheat PKABA1. RNA blot analysis indicated that ABA induced, but GA suppressed, the expression of HvPKABA1 in barley seeds. Transient expression of HvPKABA1 also suppressed the GA-inducible α-amylase gene expression. These results suggest that HvPKABA1 is probably involved in the signal transduction pathway from ABA to suppress the GA-inducible gene expression. Southern blot analysis showed that HvPKABA1 is likely a single-copy gene in barley. The sequence of the genomic clone reveals that HvPKABA1 consists of eight introns, the first one being more than 6 kb long. The mapped transcription start site of this gene suggests that it may have a TATA-less promoter.