cDNAs encoding an enzyme with UDP-glucose:cyclo-DOPA 5-O-glucosyltransferase activity were isolated from four o'clocks and feather cockscombs. Phylogenetic analysis of the amino acid sequences deduced from the cDNAs show that they represent a single subclade distinct from those of other phenylpropanoid and flavonoid glucosyltransferases. Changes in the amount of transcripts of the cDNA in four o'clocks correlated with the accumulation of betanin during flower development. The cDNAs isolated here were candidates for the gene of the enzyme involved in another pathway of betacyanin biosynthesis via glucosylation at the cyclo-DOPA step rather than at the betanidin step.