Phylogenomics of the psychoactive mushroom genus <i>Psilocybe</i> and evolution of the psilocybin biosynthetic gene cluster

Abstract

Psychoactive mushrooms in the genus <i>Psilocybe</i> have immense cultural value and have been used for centuries in Mesoamerica. Despite the recent surge of interest in these mushrooms due to the psychotherapeutic potential of their natural alkaloid psilocybin, their phylogeny and taxonomy remain substantially incomplete. Moreover, the recent elucidation of the psilocybin biosynthetic gene cluster is known for only five of ~165 species of <i>Psilocybe</i>, four of which belong to only one of two major clades. We set out to improve the phylogeny of <i>Psilocybe</i> using shotgun sequencing of fungarium specimens, from which we obtained 71 metagenomes including from 23 types, and conducting phylogenomic analysis of 2,983 single-copy gene families to generate a fully supported phylogeny. Molecular clock analysis suggests the stem lineage of <i>Psilocybe</i> arose ~67 mya and diversified ~56 mya. We also show that psilocybin biosynthesis first arose in <i>Psilocybe</i>, with 4 to 5 possible horizontal transfers to other mushrooms between 40 and 9 mya. Moreover, predicted orthologs of the psilocybin biosynthetic genes revealed two distinct gene orders within the biosynthetic gene cluster that corresponds to a deep split within the genus, possibly a signature of two independent acquisitions of the cluster within <i>Psilocybe</i>.