Effect of epigenetic factors and cis-regulatory motifs on the expression of FUM1, a key fumonisin biosynthetic gene in Fusarium verticillioides

Fumonisins are a family of mycotoxins (produced by Gibberella moniliformis, anamorph Fusarium verticillioides) that contaminate maize and maize-based products and cause great concern for human and animal health. Fumonisins are inducible under certain conditions, and their accumulation seems to correlate well with the amount of transcripts from some of their biosynthetic genes, namely of FUM1. In all eukaryotic organisms, acetylation of core histones and DNA methylation degree play a key role in the regulation of transcription, along with promoter regions within individual genes. With this work, we wanted to explore the possibility that both specific cis-regulatory motifs exist on the FUM1 promoter region (pFUM1), and/or that epigenetic mechanisms (histone acetylation/deacetylation, DNA methylation) may be important for FUM1 expression and therefore for fumonisin production. Results of an in silico analysis suggest the presence of a 6-bp sequence statistically over-represented in the biosynthetic gene promoters, compared to the rest of the genome. This motif is repeated twice in pFUM1; its importance for FUM1 expression is being validated by qRT-PCR analysis of targeted deletion mutants. Also, we followed FUM1 expression after treatment with a histone deacetylase inhibitor, and investigated the methylation of pFUM1 under fumonisin-inducing and non-inducing conditions. Preliminary results here suggest that both histone acetylation and a variation in pFUM1 methylation degree may contribute to FUM1 expression under inducing conditions in vitro.