Identification and Analysis of a Putative Regulatory Motif in FUM1, the FUM Cluster Key Gene for Fumonisin Biosynthesis in Fusarium verticillioides

Fumonisins are mycotoxins produced mainly by the pathogenic fungus Fusarium verticillioides (teleomorph Gibberella moniliformis) that contaminates maize-based food and feed, causing several diseases both in humans and animals. The fumonisin biosynthetic pathway is encoded by the so-called FUM gene cluster. Biosynthetic genes within secondary metabolite gene clusters are typically regulated by pathway-specific transcription factors, so FUM gene cluster is probably co-regulated at transcriptional level. To study the genetic and environmental factors involved in fumonisin production, we performed bioinformatic analyses on the FUM genes putative promoter sequences. Results suggested the presence of a 6-bp sequence statistically over-represented in the FUM gene promoters, compared to the rest of the genome. This motif could cis-act on the regulation of FUM genes and notably of FUM1, since it is repeated twice in its putative promoter sequence (pFUM1). To validate the in silico prediction, a pFUM1 synthetic version with this motif mutated (pFUM1mut) was obtained. Both wt pFUM1 and pFUM1mut sequences were used to drive the GFP expression in transgenic Fv strains. Molecular characterization and transcripts quantification by qRT-PCR of endogenous FUM1 and GFP in Fv transformants are under way; this will allow us to validate the role of the identified motif in FUM1 expression.