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This discovery, to be published Thursday in the journal Nature,
suggests that fungi have the capacity to rapidly change the makeup of
their genomes and become infectious to plants and possibly animals,
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
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
“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
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
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
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.
Source : Oregon State University
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