Gene-enzyme relations in the pathway of flavonoid biosynthesis in barley.

Mutations in genes associated with the pathway of flavonoid biosynthesis can be easily induced in barley, and more than 600 mutants have been isolated in which the biosynthesis of proanthocyanidins is genetically blocked. Diallelic crosses have localized a majority of the proanthocyanidin-free mutants to nine different ant genes. In order to characterize the ant gene assays for flavanone 3-hydroxylase, flavonoid 3'-hydroxylase and dihydroflavonol reductase activities in protein extracts from developing grains of proanthocyanidin-free mutants in six ant genes and wild-type barley were performed. The presence of chalcone synthase enzyme protein in wild-type barley and the mutant ant 13-152 was investigated by SDS-PAGE, protein blotting, and reaction with an antiserum against parsley chalcone synthase. The results of these experiments combined with earlier studies of flavonoid content in barley grains of different genotypes characterize the functions of six ant genes as follows. The gene ant 13 is a regulatory gene affecting the transcription of structural genes in the flavonoid pathway. The genes ant 17 and ant 22 are probably coding for different components necessary for hydroxylation of flavanones in 3-position. The gene ant 18 is the structural gene coding for dihydroflavonol reductase, and ant 19 is most likely the structural gene coding for leucoanthocyanidin reductase. Ant 21 is probably a regulatory gene affecting the biosynthesis of proanthocyanidins and anthocyanins.