Gene conservation reveals perylenequinone toxin biosynthesis clusters in multiple plant pathogenic fungal species
Rebecca Spanner: North Dakota State University
<div>Perylenequinones are a family of structurally related secondary metabolite fungal toxins that absorb light energy to produce reactive oxygen species. This potent mechanism serves as an effective weapon for plant pathogens in disease establishment. The foliar sugar beet pathogen <em>Cercospora beticola </em>secretes its namesake perylenequinone cercosporin during infection. Recent studies have shown that the cercosporin toxin biosynthesis cluster is present in other plant pathogenic fungal species outside of the genus <em>Cercospora</em>. For the apple fruit pathogen <em>Colletotrichum fioriniae</em>, the production of cercosporin <em>in vitro </em>was demonstrated and we are investigating the role of the toxin in post-harvest decay of apple via gene expression studies. These results have prompted the search for biosynthetic gene clusters of structurally-similar perylenequinones in other fungi. We report the identification of the elsinochrome biosynthetic cluster of <em>Elsinoë fawcettii </em>based on gene cluster conservation and validation by targeted gene replacement. Phylogenetic analysis of the core polyketide synthase encoding genes as well as alignment of putative melanin clusters revealed high conservation between established <em>Magnaporthe grisea</em> and newly identified <em>C. beticola</em>, <em>E. fawcettii</em>, and <em>Cladosporium phlei</em> melanin pathways. Our results emphasize the high conservation level between biosynthetic clusters of structurally related secondary metabolites and how it can be exploited as a reliable method to identify new biosynthetic pathways that are of agronomic importance.</div>
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