Molecular cloning, sequence analysis, and in vitro expression of flavanone 3β-hydroxylase from Petunia hybrida

A cDNA encoding flavanone 3β-hydroxylase was isolated from petals of Petunia hybrida. The open reading frame of the nearly full length cDNA coded for a 369-amino acid polypeptide with a calculated M_r of 41,466. The function of this nucleotide sequence was verified by comparison with amino acid sequence of the amino terminus and tryptic peptides from purified plant enzyme, by Northern blotting with RNA from wild type and mutant plants, and by prokaryotic expression yielding an enzymatically active hydroxylase. Computer-aided sequence analysis revealed high similarity (73.5%) to flavanone 3β-hydroxylase from barley. Genomic Southern blot analysis showed the presence of only one gene for flavanone 3β-hydroxylase in P. hybrida.