LAUSR

Significance Why do unrelated poisonous mushrooms (Amanita, Galerina, and Lepiota) make the same deadly toxin, α-amanitin? One of the most effective and fast strategies for organisms to acquire new abilities is through horizontal gene transfer (HGT). With the help of genome sequencing and the finding of two genes for the amanitin biosynthetic pathway, we demonstrate that the pathway distribution resulted from HGT probably through an unknown ancestral fungal donor. In Amanita mushrooms, the pathway evolved, through a series of gene manipulations, to produce very high levels of toxins, generating “the deadliest mushroom known to mankind.”