Toxic Transfer

These mushrooms were involved in a very poisonous relationship.

Three mushrooms known as the destroying angel, the deadly dapperling and the funeral bell all have something in common : the fabulously lethal toxin alpha-Amanitin.

If you eat one of these mushrooms, symptoms may not appear for several hours. But soon enough, the toxin begins wreaking havoc on your body's ability to transcribe genes. By the fourth day or so after consumption, your liver and kidneys begin to fail. After about a week you may well die.

This uncanny deadliness has a mystery at its core :

These mushrooms are from three separate genera, or groups of fungal species, that are not closely related. How do they come to make the same exact toxin?

In a new paper, scientists who have sequenced genomes of 15 species of mushrooms from these three groups make an intriguing claim :

The genes to make alpha-Amanitin, rather than being inherited from a shared ancestor of these groups, were transferred to them directly from an unknown, probably extinct mushroom.

This kind of gene transfer, called horizontal gene transfer, is common among bacteria, said Hong Luo, a researcher in China and an author of the new paper. Little snippets of DNA are passed from one microbe to another, then passed on to their offspring.

However, mounting evidence suggests that somehow, genes can move among complex, multicellular creatures as well as, perhaps with help from pathogens. [Veronique Greenwood]


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