avnA, a gene encoding a cytochrome P-450 monoxygenase, is involved in the conversion of averantin to averufin in aflatoxin biosynthesis in Aspergillus parasiticus

The avnA gene from the filamentous fungi Aspergillus flavus, corresponding to one of the two transcripts found between the ver-1 and omtA genes on the gene cluster involved in the aflatoxin biosynthetic pathway, was sequenced. Its nucleotide sequence has a coding region for a protein of 495 amino acids with a molecular mass of 56.3 kDa. The gene is composed of three exons and two introns. Disruption of the avnA gene in the wild-type aflatoxigenic A. parasiticus strain produced a nonaflatoxigenic mutant which accumulated a bright yellow pigment.