Comparison of the omtA genes encoding O-methyltransferases involved in aflatoxin biosynthesis from Aspergillus parasiticus and A. flavus.

O-methyltransferase (OMT) is one of the key enzymes in aflatoxin (AF) biosynthesis in the fungi, Aspergillus flavus (Af) and A. parasiticus (Ap). Genomic DNA clones containing the omtA genes from Ap strain SRRC 143 and Af strain CRA01-2B were sequenced. Comparison of the genomic DNA sequences with the cDNA of this Ap gene revealed the presence of four introns ranging from 52 to 60 bp in length in both species; the region encoding the putative S-adenosylmethionine-binding motif was located between the third and fourth introns. The coding sequence of omtA from Ap strain SRRC 143 demonstrated a greater than 97% sequence identity with that from Af strain CRA01-2B, within the coding region.