Convergent evolution of psilocybin biosynthesis by psychedelic mushrooms

Psilocybin, the psychoactive compound found in dozens of mushroom species, is being studied for treating addiction, depression, and end-of-life suffering. New genome analyses of the hallucinogenic mushrooms Psilocybe cyanescens and Pluteus salicinus confirm and refine the genes responsible for psilocybin biosynthesis, showing that a previously implicated transcription factor is not part of that gene cluster. The mushroom Inocybe corydalina produces psilocybin but lacks the established cluster, and an alternative cluster is described. Meta-transcriptome analysis of wild mushrooms reveals gene expression from fly larvae growing inside Psilocybe cyanescens, and these larvae were reared to adulthood. Psilocybin does not fully protect against insect consumption, suggesting its ecological role as a defense compound may need rethinking.

Study at a glance

Abstract

Abstract Psilocybin is a psychoactive compound with clinical applications produced by dozens of mushroom species 1 . There has been a longstanding interest in psilocybin research with regard to treatment for addiction 2 , depression 3 , and end-of-life suffering 4 . However, until recently very little was known about psilocybin biosynthesis and its ecological role. Here we confirm and refine recent findings 5 about the genes underpinning psilocybin biosynthesis, discover that there is more than one psilocybin biosynthesis cluster in mushrooms, and we provide the first data directly addressing psilocybin’s ecological role. By analysing independent genome assemblies for the hallucinogenic mushrooms Psilocybe cyanescens and Pluteus salicinus we recapture the recently discovered psilocybin biosynthesis cluster 5,6 and show that a transcription factor previously implicated in its regulation is actually not part of the cluster. Further, we show that the mushroom Inocybe corydalina produces psilocybin but does not contain the established biosynthetic cluster, and we present an alternative cluster. Finally, a meta-transcriptome analysis of wild-collected mushrooms provides evidence for intra-mushroom insect gene expression of flies whose larvae grow inside Psilocybe cyanescens . These larvae were successfully reared into adults. Our results show that psilocybin does not confer complete protection against insect mycophagy, and the hypothesis that it is produced as an adaptive defense compound may need to be reconsidered.