VeA Regulates Conidiation, Gliotoxin Production, and Protease Activity in the Opportunistic Human Pathogen Aspergillus fumigatus

Invasive aspergillosis by Aspergillus fumigatus is a leading cause of infection-related mortality in immunocompromised patients. In this study, we show that veA, a major conserved regulatory gene that is unique to fungi, is necessary for normal morphogenesis in this medically relevant fungus. Although deletion of veA results in a strain with reduced conidiation, overexpression of this gene further reduced conidial production, indicating that veA has a major role as a regulator of development in A. fumigatus and that normal conidiation is only sustained in the presence of wild-type VeA levels. Furthermore, our studies revealed that veA is a positive regulator in the production of gliotoxin, a secondary metabolite known to be a virulent factor in A. fumigatus. Deletion of veA resulted in a reduction of gliotoxin production with respect to that of the wild-type control. This reduction in toxin coincided with a decrease in gliZ and gliP expression, which is necessary for gliotoxin biosynthesis. Interestingly, veA also influences protease activity in this organism. Specifically, deletion of veA resulted in a reduction of protease activity; this is the first report of a veA homolog with a role in controlling fungal hydrolytic activity. Although veA affects several cellular processes in A. fumigatus, pathogenicity studies in a neutropenic mouse infection model indicated that veA is dispensable for virulence.