Embargoed until 2 p.m. EDT
NSF PR 01-52 - June 20, 2001
Media contact:
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Cheryl Dybas
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Program contact:
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Jim Rodman
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jrodman@nsf.gov
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Important Pathogens and Cures Belong to Little-Known
Group of Fungi
Research points way to discovering other agents
Researchers studying medicinal, pharmacological, antibiotic,
carcinogenic and food-production agents would do well
to look at an often-overlooked group of fungi that
once had -- but then lost -- the ability to form lichen
symbioses, according to a National Science Foundation
(NSF)-funded study published this week in the journal
Nature.
"The research challenges the common notion that mutualistic
symbioses are endpoints of evolution," says James
Rodman, program director in NSF's division of environmental
biology.
Using DNA sequence data, the scientists have determined
a more accurate fungus family tree and reconstructed
the evolution of lichen symbiosis. As a result, a
little-understood group of lichen-forming fungi is
now recognized as more important to humans than previously
thought. Better insight into animal and human diseases
caused by fungi may be derived from studying the distinction
between fungi that never formed lichen symbioses during
their evolution, and those that did but later lost
the ability.
Lichens grow on many different substrates such as rocks,
soils or trees, and in dry to aquatic habitats from
the tropics to the poles. About one-fifth of all known
fungi form lichens. Years ago, scientists thought
that lichen-forming fungi were a sideshow, a small,
closely-knit fringe group. This study demonstrates
that lichen-forming fungi originated much earlier
than previously thought. Therefore, lichen symbiosis
has played a larger-than-expected role in the evolution
of fungi.
"Phylogenies coupled with statistical methods that
reconstruct ancestral states can help identify additional
species with possible benefits, and provide a better
understanding of fungi that are detrimental to humans,"
says François Lutzoni, assistant curator of
botany at The Field Museum in Chicago and lead author
of the study. "This is one of many reasons why reconstructing
the complete tree of life is so compelling and should
be one of the main scientific endeavors of the new
millennium."
This study demonstrates that lichen-forming fungi are
especially important to humans. It determined for
the first time that several groups of non-lichen-forming
fungi, including species with both beneficial and
detrimental properties to humans, are derived from
lichen ancestors.
The authors speculate about why other important fungal
species might be found within this secondarily-derived,
non- lichen-forming category of fungi.
"When a fungus loses its ability to form a lichen symbiosis,
some of the genes involved in that process may be
diverted to new functions that inadvertently offer
possible benefits or detriments to humans," says Mark
Pagel, co-author of the paper. Pagel is affiliated
with the School of Animal and Microbial Sciences of
the University of Reading (UK).
The research concludes that loss of the ability to
form a lichen outstripped gains by three to two, at
least for the genus Ascomycota, which includes 98
percent of known lichenized fungal species.
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