By Stephanie Schupska
University of
Georgia
Millions of years. That’s the time period Andrew Paterson works
with in his research. He’s searching for clues as to why a
certain plant turned out the way it did, why a certain gene was
preserved and another discarded.
His current research at the University of Georgia centers on
polyploids, organisms that have twice the normal number of
chromosomes. His findings were published online Feb. 8 in
the “Proceedings of the National Academy of Sciences of the
United States of America” (PNAS).
“We each have one chromosome from mom and one from dad,” said
Paterson, director of UGA’s Plant Genome Mapping
Laboratory. “Once in a long while, the reproductive process
makes an error. It makes four, two from each parent. Only a
fraction of these organisms survive.”
Plants are much more tolerant of such errors than animals. By
studying those plants that have survived, Paterson hopes to
find answers to which extra genes a plant keeps and which it
discards, a choice that continues to shape the world.
“I think there will be quite a lot of interest in this
research,” Paterson said of the study of polyploids. “People
are realizing that polyploids are more common than they
thought. It was surprising that rice was an ancient polyploid.
I think that the role of genetic duplication and polyploidy in
evolution has generally been underestimated.”
Paterson’s PGML colleague, John Bowers, built the groundwork;
and former UGA graduate student Brad Chapman started the
present experiment in 2003 as part of his dissertation.
Paterson’s lab is doing a follow-up study to “ask what happens
to genes after they’re duplicated,” he said. “Dr. Bowers’
research set the structure for asking questions.”
Before Paterson published his study, scientists believed that
polyploid genes would change quickly. “We found the opposite,
that duplicated genes change slowly,” he said.
In his article, Paterson says that “genome duplication, a
punctuational event in the evolution of a lineage, is more
common than previously suspected.” At the same time, he says,
there is actually less species-wide polymorphism than
scientists had thought.
This particular study centers on rice and Arabidopsis, a small
flowering plant commonly called thale cress or mouse-ear cress.
It’s related to cabbage and mustard. These plants were
traditionally thought to be diploids. But Bowers, Paterson and
Chapman showed them to be ancient polyploids.
Paterson said major crops such as cotton, wheat, soybeans,
maize (corn), sugar cane, alfalfa, potatoes, tobacco and some
grasses are recent polyploids. They genetically mutated from
10,000 to a few million years ago.
Research suggests that all plants, and even mammals, may be
ancient polyploids, he said. In recent years, scientists have
successfully made artificial polyploids. This work could lead
to their more effective use to improve crops.
(Stephanie Schupska is a news editor with the University of
Georgia College of Agricultural and Environmental Sciences.)
