The AreA Nitrogen Catabolite Repression Activator Balances Fungal Nutrient Utilization and Virulence in the Insect Fungal Pathogen Beauveria bassiana

In
many fungi, the AreA GATA-type transcription factor mediates
nitrogen catabolite repression affecting fungal development and, where
applicable, virulence. Here, we investigated the functions of AreA
in the fungal entomopathogen and plant endophyte Beauveria
bassiana using knockdown of gene expression. The antiAreA mutants were impaired in nitrogen utilization and
showed increased sensitivities to osmotic stressors but increased
tolerances to oxidative/hypoxia stresses. Repression of BbAreA caused overall minimal effects on fungal virulence. The minor effects
on virulence appeared to be due in part to competing secondary effects
where host defense phenoloxidase activity was significantly decreased,
but production of the fungal metabolite oosporein was increased and
hyphal body development was impaired. Knockdown of BbAreA expression also resulted in impairment in ability of the fungus
to associate with host plants. These data implicate that BbAreA likely
acts as a regulator to balance fungal nutrient utilization, pathogenicity,
and mutualism, facilitating the fungal occupation of host niches.