Role of the osaA Gene in Aspergillus fumigatus Development, Secondary Metabolism and Virulence

is the leading cause of aspergillosis, associated with high mortality rates, particularly in immunocompromised individuals. In search of novel genetic targets against aspergillosis, we studied the WOPR transcription factor OsaA. The deletion of the gene resulted in colony growth reduction. Conidiation is also influenced by ; both deletion and overexpression resulted in a decrease in spore production. Wild-type expression levels of are necessary for the expression of the conidiation regulatory genes , , and . In addition, is necessary for normal cell wall integrity. Furthermore, the deletion of resulted in a reduction in the ability of to adhere to surfaces, decreased thermotolerance, as well as increased sensitivity to oxidative stress. Metabolomics analysis indicated that deletion or overexpression led to alterations in the production of multiple secondary metabolites, including gliotoxin. This was accompanied by changes in the expression of genes in the corresponding secondary metabolite gene clusters. These effects could be, at least in part, due to the observed reduction in the expression levels of the and global regulators when the locus was altered. Importantly, our study shows that is indispensable for virulence in both neutropenic and corticosteroid-immunosuppressed mouse models.