Ribosomal biosynthesis of α-amanitin in Galerina marginata

► Genome sequencing of Galerina marginata revealed two genes encoding alpha-amanitin. ► G. marginata produces amanitins on ribosomes, like mushrooms in the genus Amanita. ► The 35-amino acid proproteins are highly divergent from those of A. bisporigera. ► G. marginata has two prolyl oligopeptidase (POP) genes. ► On several grounds, POPB is involved in processing of the propeptide.