SEQUENCE VARIABILITY IN HOMOLOGS OF THE AFLATOXIN PATHWAY GENE AFLR DISTINGUISHES SPECIES IN ASPERGILLUS SECTION FLAVI

The Aspergillus parasiticus aflR gene, a gene that may be involved in the regulation of aflatoxin biosynthesis, encodes a putative zinc fing er DNA-binding protein. PCR and sequencing were used to examine the pr esence of aflR homologs in other members of Aspergillus Section Flavi. The predicted amino acid sequences indicated that the same zinc finge r domain, CTSCASSKVRCTKEKPACARCIERGLAC, was present in all of the Aspe rgillus sojae, Aspergillus flavus, and Aspergillus parasiticus isolate s examined and in some of the Aspergillus oryzae isolates examined. Un ique base substitutions and a specific base deletion were found in the 5' untranslated and zinc finger region; these differences provided di stinct fingerprints. A. oryzae and A. flavus had the T-G-A-A-X-C finge rprint, whereas A. parasiticus and A. sojae had the C-C-C-C-C-T finger print at the corresponding positions. Specific nucleotides at position s -90 (C or T) and -132 (G or A) further distinguished ii. flavus from A. oryzae and A. parasiticus from A. sojae, respectively. A. sojae AT CC 9362, which was previously designated A. oryzae NRRL 1988, was dete rmined to be a A. sojae strain on the basis of the presence of the cha racteristic fingerprint, A-C-C-C-C-C C-T, The DNAs of other members of Aspergillus Section Flavi, such as Aspergillus nomius and Aspergillus tamarii, and some isolates of A. oryzae appeared to exhibit low level s of similarity to the A. parasiticus aflR gene since low amounts of P CR products or no PCR products were obtained when DNAs from these stra ins were used.