Davis, California
September 23, 2008
Researchers at the
University of California, Davis
have identified a plant protein that is a key player in
moderating resistance to infectious disease. The discovery has
significant implications for medical and agricultural
researchers, particularly those working to improve global rice
production.
The protein, called XB15, keeps the plant's immune response from
overreacting and damaging the plant.
Findings from the study, led by UC Davis rice geneticist
Pamela Ronald, were published today in the journal
The Public Library of
Science Biology.
For more than 20 years, Ronald and her colleagues have been
working to better understand the genetics behind how rice plants
respond to the environment. They have developed rice plants that
can better withstand environmental stresses, such as flooding
and infectious diseases.
In 1995, the Ronald lab identified a protein in rice that serves
as a "pathogen recognition receptor." Such receptors are
proteins found in virtually all higher organisms and are key to
controlling the plant and animal response to infection. The
researchers found that this particular receptor in rice -- known
as XA21 -- was very similar to proteins in humans and other
animals that control the innate immune response.
While such immune responses are critical to the survival of the
plant or animal, they do come at a cost. In fact, in humans, the
failure to regulate these responses can lead to various
diseases, including some cancers.
Scientists have found that most plants or animals have built-in
biochemical moderators, known as negative regulators, which keep
an organism's immune response in check. These negative
regulators make sure that a defense against a perceived pathogen
is only mounted when truly needed.
In this recent study, Ronald and her colleagues identified a
negative regulator for the XA21 pathogen recognition receptor --
a protein they named XB15.
"This finding gives us a better understanding of how the innate
immune response is controlled," said Ronald, who chairs UC
Davis' Plant Genomics Program.
Ronald and colleagues have shown that rice plants carrying an
altered XB15 protein have enhanced resistance to bacterial leaf
blight, which causes a serious bacterial disease of rice. They
also discovered that if this protein is excessively produced in
rice plants carrying the XA21 resistance gene, it could actually
compromise the plant's ability to defend against the disease.
"This information should help us to develop hardier, more
productive rice plants that can better meet the worldwide demand
for rice," Ronald said. She noted that in parts of Asia,
bacterial leaf blight has been known to reduce annual rice
yields by as much as 60 percent.
"Rice is the staple food for more than half the world's
population," Ronald said. "In developing countries, such
significant crop losses translate directly into human
suffering."
Collaborating on this study with Ronald were Chang-Jin Park,
Ying Peng, Xuewei Chen, DeLing Ruan, Patrick E. Canlas and
Rebecca Bart, all of UC Davis, and Christopher Dardick, formerly
of the Ronald lab and now at the U.S. Department of
Agriculture's Appalachian Fruit Research Station in
Kearneysville, W.Va.
This study was funded by the National Institutes of Health, the
U.S. Department of Agriculture and the Korea Science and
Engineering Foundation. |
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