Accessing silent chemistry in Fusarium graminearum

Despite the success microbial natural products have offered as medicines, it is increasingly difficult to source new natural product drug leads. Among cultivable microorganisms, most natural product biosynthetic gene clusters are dormant under standard laboratory culture conditions. Here I present how the advent of genetic manipulation of transcriptional regulation enables new methods to express previously silent natural products.

The Freitag lab recently identified a histone modification associated with gene silencing of secondary metabolite gene clusters in the fungus Fusarium graminearum. Preparation of an H3K27 methyltransferase inactivated F. graminearum mutant results in a fungal phenotype that constitutively expresses additional 14% of the genes responsible for the production of mycotoxins, pigments, and other secondary metabolites.

In collaboration with the Freitag lab, we subjected this kmt6 deletion mutant to RNAseq analysis and LCMS-based, metabolomics guided compound isolation. Fungal extracts of wild type and mutant were prepared over the course of a week and analyzed via LCMS to receive secondary metabolite expression profiles. Large cultures of the F. graminearum mutant kmt6 were grown in order to isolate the compounds prioritized by statistical analysis. Separation by chromatographic techniques followed by structural elucidation has resulted in the identification of several compounds that are newly expressed in the mutant strain, including novel protofusarin. All fungal metabolites were tested for human health application in anti-microbial, anti-viral, and cytotoxicity assays. A comparative study on the metabolite expression will be presented alongside structural motifs and bioassay results.