Fungal chemical warfare: the role of aflatoxin and fumonisin in governing the interaction between the maize pathogens, and .

The mycotoxigenic fungi, and , commonly co-colonize maize in the field, yet their direct interactions at the chemical communication level have not been well characterized. Here, we examined if and how the two most infamous mycotoxins produced by these species, aflatoxin and fumonisin, respectively, govern interspecies growth and mycotoxin production. We showed that fumonisin producing strains of suppressed the growth of while non-producers did not. Additionally, while aflatoxin did not inhibit growth, it did suppress fumonisin production. Fumonisin B concentration levels plummeted when challenged with a high dose of aflatoxin B or with an aflatoxin producing strain. With these findings, expression of the genetic regulators of secondary metabolism was investigated for both fungi. While no strong effect was seen on genes in the aflatoxin biosynthetic gene cluster when exposed to fumonisin B, the fumonisin repressor , which is adjacent to the cluster, was induced with expression proportionate to concentration when was challenged with aflatoxin B. We also assessed the expression of the global regulators of fungal secondary metabolism, and , and found that their expression is altered in both and when exposed to their competitor's mycotoxin. This work gives insight into the ecological roles of mycotoxins and why these fungi may produce them as weapons in the interspecies battle for resource acquisition.