Deletion of the Aspergillus flavus Orthologue ofA. nidulans fluGReduces Conidiation and Promotes Production of Sclerotia but Does Not Abolish Aflatoxin Biosynthesis

Abstract

ABSTRACTThefluGgene is a member of a family of genes required for conidiation and sterigmatocystin production inAspergillus nidulans. We examined the role of theAspergillus flavus fluGorthologue in asexual development and aflatoxin biosynthesis. Deletion offluGinA. flavusyielded strains with an approximately 3-fold reduction in conidiation but a 30-fold increase in sclerotial formation when grown on potato dextrose agar in the dark. The concurrent developmental changes suggest thatA. flavusFluG exerts opposite effects on a mutual signaling pathway for both processes. The altered conidial development was in part attributable to delayed expression ofbrlA, a gene controlling conidiophore formation. Unlike the loss of sterigmatocystin production byA. nidulans fluGdeletion strains, aflatoxin biosynthesis was not affected by thefluGdeletion inA. flavus. InA. nidulans, FluG was recently found to be involved in the formation of dehydroaustinol, a component of a diffusible signal of conidiation. Coculturing experiments did not show a similar diffusible meroterpenoid secondary metabolite produced byA. flavus. These results suggest that the function offluGand the signaling pathways related to conidiation are different in the two related aspergilli.