Genetic Control of Flavonoid Biosynthesis in Barley

Abstract

Mutations in genes associated with the pathway of flavonoid biosynthesis can readily be induced in barley and since 1977 more than 700 mutants have been isolated in which the biosynthesis of anthocyanin and/or proanthocyanidin is affected. Diallelic crosses have localized a majority of the mutants to 28 different complementation groups (Ant genes). Mutations in ten of the Ant genes result in a blocked synthesis of proanthocyanidins in the testa layer of the grains, whereas mutations in 18 Ant gene loci only affect anthocyanin synthesis in various organs of the plants. Seven Ant genes have been localized to a chromosome. A number of investigations have been carried out to characterize the ten known Ant genes acting on the biosynthesis of proanthocyanidins. Grains of mutants in different Ant genes and wildtypes were analyzed for contents of flavonoids and other phenolic compounds and the activity levels of several of the enzymes in the flavonoid pathway were studied. The gene locus Ant 18 has been isolated both in the form of cDNA and genomic clones. Ant 17, Ant 18, Ant 19, Ant 22, and Ant 26 are structural genes. Ant 13 is a regulatory gene coding for a transcription factor necessary for transcription of at least three structural genes in the flavonoid pathway. The action of the genes Ant 21, Ant 25, Ant 27, and Ant 28 is not fully understood. They might be regulatory genes.