Genetic material from fungi collections helped a team of researchers resolve the mushroom 'tree of life,' a map of the relationships between key mushroom species and their evolutionary history that scientists have struggled to piece together for more than 200 years.
From: Perdue University
May
22, 2015 -- The group used DNA from frozen, heat-dried and freeze-dried
specimens to analyze a dataset of 39 genomes representing most of the known
families in Agaricales (ah-gehr-ah-KAY-leez), the order that houses some of the
most familiar kinds of mushrooms, including cultivated edible mushrooms, magic
mushrooms and the deadly destroying angel. High-throughput sequencing
technology allowed the scientists to define seven new suborders and the
"trunk" of the Agaricales tree, providing a framework for testing
hypotheses of the evolution of mushrooms.
"Mycology really is one of the last
frontiers in biology," said Catherine Aime, associate professor of
mycology, the study of fungi. "We know there are six to 20 times more
species of fungi than plants, but we don't really know much about them. People
have tried to figure out how mushrooms are related since the time of Linnaeus.
It's gratifying to finally solve this mystery."
Fungi are essential to the health of
ecosystems, plants and animals. They decompose fallen wood and other organic
matter, breaking down material and freeing up nutrients for other organisms.
Most land plants rely on beneficial fungi to deliver water and other nutrients,
and the gut fungi of ruminants such as cows play a vital role in digestion.
Most humans also host fungi, which help maintain the balance of our natural
flora.
But despite their importance and rich
diversity, comparatively little is known about fungi. Many species have
"cryptic and unpredictable life histories," Aime said, making them
difficult to study. The vast majority of fungi are microscopic with few orders
producing visible mushrooms. Some species have complicated lifecycles that have
no analogy in other multicellular organisms. Others are extremely rare and
represented by only a few records or are impossible to detect with conventional
methods.
The elusiveness of fungi is one reason
why fungaria -- collections of preserved fungal specimens -- are so valuable,
Aime said. They offer a panorama of the diversity of known fungi and are often
the only places where rare species can be studied.
"To go out and recollect many of
these specimens from nature would take decades, if not lifetimes," she
said.
But until recently, fungaria were of
limited use for genetic research because of the technical complexity of genome
sequencing and the poor quality of DNA samples obtained from old, dried
specimens. Advances in technology, however, enabled Aime and her fellow
researchers to use short DNA sequences from fungaria at Purdue and Kew to knit
together entire genomes and identify genes that could be used as markers to
link related species of mushrooms, resulting in the tree of life.
The tree provides the clearest and most
detailed glimpse to date of the fundamental relationships between mushrooms and
when certain types may have evolved. Aime said that the tree suggests the
earliest Agaricales were decomposers or biotrophs, organisms that derive their
nutrition from other living organisms, a category that includes pathogens.
"We've had this view that organisms
became more 'selfish' as they evolved, learning how to take advantage of the
system by becoming pathogens," she said. "But it's possible that
selfishness happened first, and over time, some of these species coevolved to
become more mutualistic."
Aime said that the study also
highlighted the importance of fungaria as scientific resources for the genomic
age.
"We may be on the verge of a major
collections-based revolution," she said. "People think of fungaria as
similar to stamp collections -- they're not. These collections anchor our
concepts of everything in biology and are our only repositories for some dying
or possibly already-extinct species. It's extraordinarily important that we try
to collect and preserve as many species as we can. Future technology may allow
us to use those materials in ways we can't even imagine now. We've got to get
them before they go."
https://www.sciencedaily.com/releases/2015/05/150522141336.htm
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