NSF PR 02-95 - November 26, 2002
Plant-Fungal Symbiosis Found in High-Heat Extreme
Researchers examining plants growing in the geothermal
soils of Yellowstone National Park and Lassen Volcanic
National Park have found evidence of symbiosis between
fungi and plants that may hold clues to how plants
adapt to and tolerate extreme environments.
The research was funded in part through the National
Science Foundation's (NSF) Microbial Observatories
Program and published in the Nov. 22 issue of the
Biologists Regina Redman of the University of Washington
and Joan Henson of Montana State University and their
colleagues examined 200 samples of Dichanthelium
lanuginosum, also called "Geyser's Dichanthelium,"
for fungal colonization. They found what may be a
new species of the fungus Curvularia that
survives only in temperatures greater than 98 degrees
when it associates with plants.
The researchers suggest that thermotolerance may occur
through symbiotic mechanisms like heat dissipation
by pigment, such as melanin, or the activation of
a "biological trigger" that tells the plant to react
to temperature changes more rapidly or strongly than
plants that lack the fungus.
The researchers grew sample plants with and without
the symbiotic fungus in a laboratory and heated the
soil to test thermal resistance. The plants without
the fungus shriveled at 122 degrees, whereas those
plants with the fungus tolerated the heat for three
days. The plants were also subjected to intermittent
temperatures as high as 149 degrees. The fungus-free
plants died, but the fungus-bearing plants survived
for 10 days.
The researchers also demonstrated that the plants provide
thermal protection to the fungus by isolating it in
plant roots that had a field soil temperature of 113
"Scientific understanding of how life can thrive in
such extreme environments is at its infancy," said
Microbiologist Matt Kane, NSF's Microbial Observatories
Program Director. "Research funded by NSF's Microbial
Observatories Program is demonstrating that when you
look in interesting places, you discovery interesting
life forms and interrelationships, such as these fungi
and their plant partners."
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