The present invention relates to an isolated nucleic acid molecule, comprising a nucleotide sequence, which encodes a polypeptide with chalcone 3-hydroxylase activity, wherein the nucleotide sequence comprises SEQ ID NO. 1 or has at least a 60% identity with SEQ ID NO. 1 or is able to hybridize with a molecule comprising the sequence of SEQ ID NO. 1, wherein the nucleotide sequence encodes a polypeptide, which comprises the motif FASRPLSX1X2G(X3)m(GSAGGD)n (SEQ ID NO. 3), wherein X1 is threonine or serine, X2 is alanine or glycine, X3 is any amino acid, m is an integer between 50 and 200, and n is 0 or 1.