Killer mushrooms!

It is thought to have been responsible for the deaths of emperors. In
parts of California’s forests, it is everywhere.

It is the deathcap mushroom, Amanita phalloides, so filled
with toxins that a single cap can kill anyone who mistakenly eats it and
does not get medical treatment. Because it looks like an edible
mushroom, the deathcap is among those most involved in human poisoning,
such as one that occurred in Newton, Mass., last fall. Through history,
it has been a convenient tool for those interested in regime change,
playing a key role in the Europe-spanning War of Austrian Succession in
the 1700s, which started when Holy Roman Emperor Charles VI died after
eating a plate of mushrooms, thought to be deathcaps.

Though much is known about the deathcap’s toxicity — it kills by
fostering liver failure — much less is understood about its general
biology and its role in the environment. Anne
Pringle, associate professor of organismic and evolutionary
biology, is out to change that.

Pringle has spent years in California’s forests, researching the
deathcaps that in some parts of the state make up as much as 80 percent
of the local biomass of mushrooms. Pringle proved first that the
California population was not native, but rather an introduced
population from Europe.

She’s working now to understand the mushroom’s dispersal across the
landscape and its symbiotic partnership with trees. Its widespread
presence begs the questions of whether it displaced native symbiotic
fungi and whether it spreads more easily as a mutualist (an organism in a
relationship beneficial to both partners) than it would as a pathogen,
which characterizes most known invasive fungi. She recently concluded
that it reproduces more readily through the spread of its spores, which
are released from the fleshy gills under its cap, than asexually through
fragmentation of its thready subterranean fungal body.

Like most mushroom-producing fungi, much of the deathcap’s body
actually lies under the Earth’s surface, and its mushrooms are
temporary, sent up from the underground filaments to release spores and
then fade. Even with the mushroom gone, the fungus still operates
underground, decomposing old plant matter and, in the case of the
deathcap, partnering with tree roots, providing nitrogen in exchange for
carbon compounds.

Pringle’s work, conducted through a combination of old-fashioned
fieldwork and cutting-edge genetic analysis, has shown that the deathcap
spreads slowly. It moves through either the slow creep of its
underground body or the floating spread of its spores, which do not
drift far from their release point.

Humans likely played a big role in the fungus’ spread. Because it
lives in association with tree roots, researchers believe it was
introduced here from Europe at least twice — once in California and once
on the East Coast — by hitching rides on trees transplanted from Europe
to America.

On the East Coast, Pringle and researchers from her lab have
identified dozens of populations: in Newton, near the New Jersey Pine
Barrens, near Rochester, N.Y., and in New Hampshire’s White Mountains.
Pringle says the populations on the East Coast are isolated, not
widespread as in California. Another difference on the East Coast is that deathcaps are associated with pine trees, not the
oaks that they partner with in California and Europe. Pringle and
doctoral student Ben Wolfe said that may be because of a slightly
different strain being introduced on the East Coast, or it may be
because of ecological constraints put on the population on the East
Coast by closely related native species, also from the genus Amanita.

Though the deathcap may be the star of Pringle’s lab, her work
includes other fungal species, as well as lichens, a symbiotic
association of fungi and algae.

Wolfe, who expects to graduate in December, is working with the U.S. Department of
Energy to decode the genome of Amanita species related to
the deathcap. He hopes to understand the genetic roots of fungal
symbiosis with trees. A bonus of decoding the fungi’s genome, Wolfe
said, would be that, in degrading plant material, the fungi produces an
enzyme called cellulase, of potential interest in biofuel processing.

In talking about her work, Pringle emphasizes the importance of
fungal conservation. Fungi have not received the attention that plants
and animals have, so less is known about them. With the planet
undergoing an extinction crisis, we may be losing fungal species before
we even know they’re here, Pringle said.