CONTROL OF EXPRESSION PATTERNS OF ANTHOCYANIN STRUCTURAL GENES BY 2 LOCI IN THE COMMON MORNING GLORY

Two loci producing white flowers have been identified in the common mo rning glory, Ipomoea purpurea. At the W locus, ww individuals produce flowers with white corollas and pigmented rays, while at the A locus, aa individuals produce flowers with white corollas, and aa* individua ls produce variegated corollas. To determine whether these two loci co rrespond to regulatory or structural genes, six structural genes requi red for anthocyanin synthesis were cloned and their expression pattern was examined in genotypes with white and pigmented flowers. In ww flo wer buds, expression of all six structural genes was greatly reduced o r eliminated, indicating that the W locus encodes a regulatory gene. B y contrast, genotype at the A locus did not affect expression of any o f the structural genes, suggesting that the A locus may encode one of those structural genes. An evolutionary comparison of structural gene regulation in maize, snapdragons, petunias, and morning glories sugges ts that regulatory control of the anthocyanin pathway is evolutionaril y labile.