Provided is a polynucleotide encoding a protein having activity that transfers a sugar to the hydroxyl group at the 4′-position of a flavone, wherein the polynucleotide is selected from the group consisting of: (a) a polynucleotide composed of the base sequence of SEQ ID NO: 1 (b) a polynucleotide that hybridizes under stringent conditions with a polynucleotide composed of a base sequence complementary to the base sequence of SEQ ID NO: 1 (c) a polynucleotide encoding a protein composed of the amino acid sequence of SEQ ID NO: 2 and, (d) a polynucleotide encoding a protein composed of an amino acid sequence in which one or a plurality of amino acids have been deleted, substituted, inserted and/or added in the amino acid sequence of SEQ ID NO:2.
