Signaling events connecting mycotoxin biosynthesis and sporulation in Aspergillus and Fusarium spp.

Abstract

Secondary metabolite production and sporulation are tightly co-regulated in the Aspergilli and Fusaria. Here we discuss two conserved pathways, including a G-protein/cAMP/Protein kinase A cascade and an oxylipin-mediated signalling process, that genetically link sporulation and secondary metabolism in these genera. The G-protein alpha subunit FadA negatively regulates aflatoxin and cyclopiazonic acid production in Aspergillus, and positively regulates penicillin production in A. nidulans and tricothecene production in Fusarium sporotrichiodes. Inactivation of FadA eliminates or decreases asexual spore production in both genera. The G-protein cascade is conserved throughout eukaryotes, and regulation of sporulation and secondary metabolism by this signal transduction pathway appears to be conserved within filamentous fungi. On the other hand, the oxylipin-mediated signalling pathway appears to be restricted to filamentous fungi. We have identified novel genes encoding putative dioxygenases likely to be responsible for secreted oxylipins which act as sporulation factors. Deletion of these genes affects asexual sporulation and secondary metabolite production in A. nidulans and F. sporotrichiodes.