Mycoviruses mediate mycotoxin regulation in Aspergillus ochraceus

To date, no demonstration of a direct correlation between the presence of mycoviruses and the quan- titative or qualitative modulation of mycotoxins has been shown. In our study, we transfected a virus- free ochratoxin A (OTA)-producing isolate of Asper- gillus ochraceus with purified mycoviruses from a different A. ochraceus isolate and from Penicillium aurantiogriseum. Among the mycoviruses tested, only Aspergillus ochraceus virus (AoV), a partiti- virus widespread in A. ochraceus, caused a specific interaction that led to an overproduction of OTA, which is regulated by the European Commission and is the second most important contaminant of food and feed commodities. Gene expression analy- sis failed to reveal a specific viral upregulation of the mRNA of genes considered to play a role in the OTA biosynthetic pathway. Furthermore, AoO- TApks1, a polyketide synthase gene considered essential for OTA production, is surprisingly absent in the genome of our OTA-producing isolate. The possible biological and evolutionary implications of the mycoviral regulation of mycotoxin production are discussed.