Culture Conditions Control Expression of the Genes for Aflatoxin and Sterigmatocystin Biosynthesis in Aspergillus parasiticus and A. nidulans

High temperature and nitrate supported gene expression for sterigmatocystin biosynthesis in Aspergillus nidulans; ammonium did not. Homologous genes for aflatoxin biosynthesis in A. parasiticus showed the opposite transcript expression pattern, suggesting that the two mycotoxins are regulated differently. The aflR gene is postulated to require additional genetic elements to effect its own activation by the different culture conditions. A patulin polyketide synthase (PKS) gene was found to be regulated differently than the aflatoxin PKS. Thus, the biosyntheses of structurally similar compounds in these two fungi appear to be regulated very differently.