Posted by Sharon on 3/18/10

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"..this study we found fungi able to transfer an infectious
capability to a different strain in a single generation,"
he said. "We've probably underestimated this phenomenon,
and it indicates that fungal strains may become pathogenic
faster than we used to think possible."

"..suggests that fungi have the capacity to rapidly change
the make-up of their genomes and become infectious to
plants and possibly animals, including humans."

"...evolution of virulence in fungal strains that was once
believed to be slow has now been shown to occur quickly,
and may force a renewed perspective on how fungi can
behave, change and transfer infectious abilities."

ScienceDaily (Mar. 17, 2010) — Fungi have significant
potential for "horizontal" gene transfer, a new study has
shown, similar to the mechanisms that allow bacteria to
evolve so quickly, become resistant to antibiotics and
cause other serious problems.

This discovery, to be published March 18 in the journal
Nature, suggests that fungi have the capacity to rapidly
change the make-up of their genomes and become infectious
to plants and possibly animals, including humans.

They are not nearly as confined to the more gradual
processes of conventional evolution as had been believed,
scientists say. And this raises issues not only for crop
agriculture but also human health, because fungi are much
closer on the "evolutionary tree" to humans than bacteria,
and consequently fungal diseases are much more difficult to
treat.

The genetic mechanisms fungi use to do this are different
than those often used by bacteria, but the end result can
be fairly similar. The evolution of virulence in fungal
strains that was once believed to be slow has now been
shown to occur quickly, and may force a renewed perspective
on how fungi can behave, change and transfer infectious
abilities.

"Prior to this we've believed that fungi were generally
confined to vertical gene transfer or conventional
inheritance, a slower type of genetic change based on the
interplay of DNA mutation, recombination and the effects of
selection," said Michael Freitag, an assistant professor of
biochemistry and biophysics at Oregon State University.

"But in this study we found fungi able to transfer an
infectious capability to a different strain in a single
generation," he said. "We've probably underestimated this
phenomenon, and it indicates that fungal strains may become
pathogenic faster than we used to think possible."

Researchers from the Center for Genome Research and
Biocomputing at OSU collaborated on this study with a large
international group of scientists, including principal
investigators from The Broad Institute in Massachusetts,
the University of Amsterdam, and the USDA Agricultural
Research Service at the University of Minnesota.

Bacteria use "horizontal" genetic transfer through
chromosomes and DNA plasmids to change quickly, which is
one reason that antibiotic resistance can often develop.
This capability was believed to be possible, but rare, in
fungi. In the new study, based on a genome-wide analysis of
three Fusarium species, it was shown experimentally that
complete chromosomes were being transferred between
different fungal strains, along with the ability to cause
infection. Various Fusarium fungi can infect both plants
and humans.

In humans, fungal infections are less common than those
caused by bacteria, but can be stubborn and difficult to
treat -- in part, because fungi are far more closely
related to animals, including humans, than are bacteria.
That limits the types of medical treatments that can be
used against them. Fungal infections are also a serious
problem in people with compromised immune systems,
including AIDS patients, and can be fatal.

According to Freitag, this new understanding of fungal
genetics and evolution is great news.

For one thing, it may help researchers to better understand
the types of fungal strains that are most apt to develop
resistance to fungicides, and help crop scientists develop
approaches to minimize that problem.

Fungal diseases are a major problem in crop agriculture,
and billions of dollars are spent around the world every
year to combat new and emerging fungal pathogens in plants,
animals and humans.

On a more basic level, this study provides evidence that
the "tree of life," with one trunk and many branches, is
outdated. It should be replaced by a "network of life" in
which many horizontal connections occur between different
species.

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