The present invention provides a protein having the amino acid sequence as
shown in SEQ ID NO: 2, 4, 6, 8, 10 or 12 or a protein having a modified
amino acid sequence thereof and having an activity of transferring an
aromatic acyl group to a sugar residue of a flavonoid; a gene, especially
cDNA, encoding the protein; and use thereof. For example, by introducing
the above gene into a plant expressing hydroxycinnamate
1-O-glucosyltransferase gene, optionally together with a cDNA encoding a
protein having the amino acid sequence as shown in SEQ ID NO: 14, 16 or
18 or a protein having an amino acid sequence derived therefrom by
modification and having an activity of glucosylating a hydroxyl group at
position 1 of hydroxycinnamic acid, and then expressing the introduced
gene(s), it is possible to acylate the sugar residue of flavonoids in
flowers of the plant to thereby confer a blue color on the flowers.