CLONING OF THE ASPERGILLUS-PARASITICUS APA-2 GENE ASSOCIATED WITH THEREGULATION OF AFLATOXIN BIOSYNTHESIS

An Aspergillus parasiticus gene, designated apa-2, was identified as a regulatory gene associate with aflatoxin biosynthesis. The apa-2 gene was cloned on the basis of overproduction of pathway intermediates fo llowing transformation of fungal strains with cosmid DNA containing th e aflatoxin biosynthetic genes nor-1 and ver-1. Transformation of an 0 -methylsterigmatocystin-accumulating strain, A. parasiticus SRRC 2043, with a 5.5-kb HindIII-XbaI DNA fragment containing apa-2 resulted in overproduction of all aflatoxin pathway intermediates analyzed. Specif ic enzyme activities associated with the conversion of norsolorinic ac id and sterigmatocystin were increased approximately twofold. The apa- 2 gene was found to complement an A. flavus afl-2 mutant strain for af latoxin production, suggesting that apa-2 is functionally homologous t o afl-2. Comparison of the A. parasiticus apa-2 gene DNA sequence with that of the A. flavus afl-2 gene (G. A. Payne, G. J. Nystorm, D. Bhat nagar, T. E. Cleveland, and C. P. Woloshuk, Appl. Environ. Microbiol. 59:156-162, 1993) showed that they shared >95% DNA homology. Physical mapping of cosmid subclones placed apa-2 approximately 8 kb from ver-1 .