There is provided a gene encoding a protein derived from, for example, snapdragons and petunias, said protein having an amino acid sequence as set forth in SEQ ID NO: 2, 8, and 10, and having an activity of transferring a glycosyl group to aurones, and a method of producing said protein using said gene. By introducing this gene into plants that do not have said gene, a yellow pigment aurone can be stabilized and plants having yellow flowers can be obtained.