THE ALCOHOL-DEHYDROGENASE GENE ADH1 IS INDUCED IN ASPERGILLUS-FLAVUS GROWN ON MEDIUM CONDUCIVE TO AFLATOXIN BIOSYNTHESIS

An Aspergillus flavus cDNA library was screened by differential hybrid ization to isolate clones corresponding to genes that are actively tra nscribed under culture conditions conducive to aflatoxin biosynthesis. One clone with a 1.28-kb insert was isolated, and its nucleotide sequ ence was determined. The nucleotide sequence of this clone had 75% DNA identity to those of the alcohol dehydrogenase genes from Aspergillus nidulans, and the putative polypeptide translated from the cDNA seque nce had 82% similarity with the amino acid sequences of the A. nidulan s proteins. Thus, this gene has been designated adh1. Southern hybridi zation analysis of genomic DNA from A. flavus indicated that there was one copy of the adh1 gene. Northern (RNA) hybridization analysis indi cated that the adh1 transcript accumulated in culture medium conducive to aflatoxin production and the timing of accumulation of adh1 transc ripts was similar to that for aflatoxin. Fusion of the promoter region of adh1 to a beta-glucuronidase reporter gene indicated that accumula tion of the adh1 transcript was the result of transcriptional activati on. These molecular data support previous physiological evidence that showed the importance of carbohydrate metabolism during aflatoxin bios ynthesis.