Expression of chalcone synthase, dihydroflavonol reductase, and flavanone-3-hydroxylase in mutants of barley deficient in anthocyanin and proanthocyanidin biosynthesis.

A barley (cv Triumph) cDNA library was screened with a cDNA probe encoding flavanone-3-hydroxylase of Antirrhinum majus. A full-length clone coding for a protein of 377 amino acids (42 kDa), with an overall homology of 71% and a central domain homology of 85% to the Antirrhinum protein, was isolated. This novel barley cDNA and two previously isolated cDNAs encoding chalcone synthase and dihydroquercetin reductase, respectively, were used to study the transcription of the corresponding genes in testa pericarp tissue from ant 13 mutants of barley. No or very low levels of transcripts are found in mutants ant 13-152, ant 13-351, and ant 13-353. It is concluded that the gene Ant 13 encodes a transcription factor operating in the flavonoid biosynthesis of barley. Transcription of the gene for the flavanone-3-hydroxylase (subunit) was also studied in an ant 17 mutant of barley. Mutant ant 17-352 transcribes the gene at normal or elevated levels. The mutant is blocked in the synthesis of dihydroquercetin and accumulates derivatives of eriodictyol, the precursor of dihydroquercetin. The combined observations suggest that Ant 17 is the structural gene for a barley flavanone-3-hydroxylase subunit, and that the mutant allele is a mutation in the structural domain of the gene.