Genome sequence of Pseudopithomyces chartarum, causal agent of facial eczema (pithomycotoxicosis) in ruminants, and identification of the putative sporidesmin toxin gene cluster

Abstract

AbstractFacial eczema (FE) in grazing ruminants is a debilitating liver syndrome induced by ingestion of sporidesmin, a toxin belonging to the epipolythiodioxopiperazine class of compounds. Sporidesmin is produced in spores of the fungus Pseudopithomyces chartarum, a microbe which colonises leaf litter in pastures. New Zealand has a high occurrence of FE in comparison to other countries as animals are fed predominantly on ryegrass, a species that supports high levels of Pse. chartarum spores. The climate is also particularly conducive for Pse. chartarum growth. Here, we present the genome of Pse. chartarum and identify the putative sporidesmin gene cluster. The Pse. chartarum genome was sequenced using single molecule real-time sequencing (PacBio) and gene models identified. Loci containing genes with homology to the aspirochlorine, sirodesmin PL and gliotoxin cluster genes of Aspergillus oryzae, Leptosphaeria maculans and Aspergillus fumigatus, respectively, were identified by tBLASTn. We identified and annotated an epipolythiodioxopiperazine cluster at a single locus with all the functionality required to synthesise sporidesmin.HighlightsThe whole genome of Pseudopithomyces chartarum has been sequenced and assembled.The genome is 39.13 Mb, 99% complete, and contains 11,711 protein coding genes.A putative sporidesmin A toxin (cause of facial eczema) gene cluster is described.The genomes of Pse. chartarum and the Leptosphaerulina chartarum teleomorph differ.Comparative genomics is required to further resolve the Pseudopithomyces clade.