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J. Slot

Iterative l-Tryptophan Methylation in Psilocybe Evolved by Subdomain Duplication

August 11, 2018 / Biology & Ethnobotany, Mushrooms / Psilocybin, Neuroscience, Papers, Pharmacology & Chemistry, Publications / By / , , , ,

Abstract

Psilocybe mushrooms are best known for their l-tryptophan-derived psychotropic alkaloid psilocybin. Dimethylation of norbaeocystin, the precursor of psilocybin, by the enzyme PsiM is a critical step during the biosynthesis of psilocybin. However, the “magic” mushroom Psilocybe serbica also mono- and dimethylates l-tryptophan, which is incompatible with the specificity of PsiM. Here, a second methyltransferase, TrpM, was identified and functionally characterized. Mono- and dimethylation activity on l-tryptophan was reconstituted in vitro, whereas tryptamine was rejected as a substrate. Therefore, we describe a second l-tryptophan-dependent pathway in Psilocybe that is not part of the biosynthesis of psilocybin. TrpM is unrelated to PsiM but originates from a retained ancient duplication event of a portion of the egtDB gene that encodes an ergothioneine biosynthesis enzyme. During mushroom evolution, this duplicated gene was widely lost but re-evolved sporadically and independently in various genera. We propose a new secondary metabolism evolvability mechanism, in which weakly selected genes are retained through preservation in a widely distributed, conserved pathway.

Blei, F., Fricke, J., Wick, J., Slot, J. C., & Hoffmeister, D. (2018). Iterative l‐Tryptophan Methylation in Psilocybe Evolved by Subdomain Duplication. ChemBioChem, 19(20), 2160-2166., 10.1002/cbic.201800336.
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Horizontal gene cluster transfer increased hallucinogenic mushroom diversity

August 16, 2017 / Mushrooms / Psilocybin, Papers, Publications / By / , , , , ,

Abstract

Secondary metabolites are heterogeneous natural products that often mediate interactions between species. The tryptophan-derived secondary metabolite, psilocin, is a serotonin receptor agonist that induces altered states of consciousness. A phylogenetically disjunct group of mushroom-forming fungi in the Agaricales produce the psilocin prodrug, psilocybin. Spotty phylogenetic distributions of fungal compounds are sometimes explained by horizontal transfer of metabolic gene clusters among unrelated fungi with overlapping niches. We report the discovery of a psilocybin gene cluster in three hallucinogenic mushroom genomes, and evidence for its horizontal transfer between fungal lineages. Patterns of gene distribution and transmission suggest that psilocybin provides a fitness advantage in the dung and late wood-decay niches, which may be reservoirs of fungal indole-based metabolites that alter behavior of mycophagous and wood-eating invertebrates. These hallucinogenic mushroom genomes will serve as models in neurochemical ecology, advancing the prospecting and synthetic biology of novel neuropharmaceuticals.

Reynolds, H. T., Vijayakumar, V., Gluck-Thaler, E., Korotkin, H. B., Matheny, P. B., & Slot, J. C. (2017). Horizontal gene cluster transfer increased hallucinogenic mushroom diversity. bioRxiv, 176347. 10.1101/176347
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