Genome sequences of Rhizopogon roseolus, Mariannaea elegans, Myrothecium verrucaria, and Sphaerostilbella broomeana and the identification of biosynthetic gene clusters for fungal peptide natural products

In recent years, a variety of fungal cyclic peptides with interesting bioactivities have been discovered. For many of these peptides, the biosynthetic pathways are unknown and their elucidation often holds surprises. The cyclic and backbone N-methylated omphalotins from Omphalotus olearius were recently shown to constitute a novel class (borosins) of ribosomally synthesized and posttranslationally modified peptides (RiPP), members of which are produced by many fungi, including species of the genus Rhizopogon. Other recently discovered fungal peptide macrocycles include the mariannamides from Mariannaea elegans and the backbone N-methylated verrucamides and broomeanamides from Myrothecium verrucaria and Sphaerostilbella broomeana, respectively. Here, we present draft genome sequences of four fungal species Rhizopogon roseolus, Mariannaea elegans, Myrothecium verrucaria and Sphaerostilbella broomeana. We screened these genomes for precursor proteins or gene clusters involved in the mariannamide, verrucamide and broomeanamide biosynthesis including a general screen for borosin-producing precursor proteins. While our genomic screen for potential RiPP precursor proteins of mariannamides, verrucamides, broomeanamides and borosins remained unsuccessful, antiSMASH predicted non-ribosomal peptide synthase (NRPS) gene clusters that may be responsible for the biosynthesis of mariannamides, verrucamides and broomeanamides. In M. verrucaria, our antiSMASH search led to a putative NRPS gene cluster with a predicted peptide product of 20 amino acids, including multiple non-proteinogenic isovalines. This cluster likely encodes a member of the peptaibols, an antimicrobial class of peptides previously isolated primarily from the Genus Trichoderma. The NRPS gene clusters discovered in our screenings are promising candidates for future research.