Untargeted Metabolomics to Investigate the Influence of Epigenetic Modifiers on the Metabolism of Fusarium verticillioides.

Toxigenic fungi are capable of producing toxic metabolites, called mycotoxins. But the presence of silent and lowly expressed genes represents the main challenge for the discovery of novel mycotoxins, especially their lesser-known forms, commonly referred to as "emerging mycotoxins." Epigenetic modifiers (EMs) are compounds that are able to alter the production of metabolites through the induction of silent biosynthetic pathways leading to an enhanced chemical diversity. The aim of this study was to assess the effects of different chemical modulators on the metabolic profiles of the well-known toxigenic fungal species, Fusarium verticillioides. Four EMs, 5-azacytidine, sodium butyrate, nicotinamide (NIC), and sodium valproate (SV), were used. Following their addition to Fusarium verticillioides cultures, the metabolic profiles were analyzed by using UHPLC-HRMS/MS under targeted and untargeted metabolomics approaches. Metabolites were putatively annotated through the use of MS-DIAL and MS-FINDER. Our results show that the treatment with SV induced the most important alteration of the secondary metabolic profile of F. verticillioides, by promoting the expression of cryptic genes. Among the 50 most discriminating metabolites across five culture conditions, 12 were fusarins or fusarin analogs. In contrast, SB and NIC had little impact on these metabolites. The study highlights SV's ability to alter gene expression by inhibiting DNA deacetylation in fungal strains. This research could have significant implications for agriculture and food industry, especially in regions facing major mycotoxin challenges.