Horizontal gene cluster transfer increased hallucinogenic mushroom diversity

Summary

Scientists discovered that distantly related hallucinogenic mushrooms produce psilocybin, the psychoactive compound in magic mushrooms, through a shared set of genes that were likely transferred between species living in similar environments like dung and decaying wood. By sequencing the genomes of three different hallucinogenic mushroom species, researchers found nearly identical gene clusters responsible for making psilocybin, and evidence showing these genes jumped between unrelated fungal lineages. This discovery suggests that fungi in dung and wood environments may be rich sources of other bioactive compounds with potential medical applications.

Background

Psilocybin is a secondary metabolite produced by phylogenetically distant mushroom-forming fungi in the Agaricales that acts as a serotonin receptor agonist. The spotty phylogenetic distribution of psilocybin among fungal species suggests possible horizontal gene transfer between unrelated fungi sharing similar ecological niches.

Objective

To identify and characterize psilocybin gene clusters in hallucinogenic mushroom genomes and provide evidence for horizontal gene transfer of these biosynthetic pathways between fungal lineages.

Results

A conserved psilocybin biosynthetic gene cluster containing five genes (PsiD, PsiM, PsiH, PsiK, PsiT) was identified in all three hallucinogenic species. Phylogenetic analyses provided evidence for horizontal transfer of the cluster between Psilocybe and Panaeolus lineages. Gene tree-species tree reconciliation supported HGT events with fewer total evolutionary events than vertical inheritance models.

Conclusion

Horizontal gene transfer of psilocybin gene clusters between distantly related dung and wood-decay fungi demonstrates that these niches share selective pressures favoring neuroactive compound production. These findings suggest such ecological niches may be reservoirs of novel bioactive molecules and provide a model for prospecting fungal pharmaceuticals.
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