April 3, 2008
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This
scanning electron micrograph shows the abnormal anatomy
of a group of developing flowers in an auxin-deficient
wei8 tar2 double mutant plant.
Credit: Jose Alonso, North Carolina State University |
Researchers at
North Carolina State University
have pinpointed a small group of genes responsible for "telling"
plants when, where and how to produce a hormone that is key to
their development. Their findings shed light on the ways in
which hormone production in plants affects both a plant's growth
and its ability to adapt to changing environments.
Dr. Jose Alonso, assistant professor of genetics, and a team of
geneticists and plant biologists from NC State, Germany and the
Czech Republic conducted the research. Their findings are
published in the April 4 edition of the journal Cell.
Plant growth and development are regulated by a small number of
hormones, which plants combine in various ways so that they can
adapt to and thrive in changing environmental conditions. Auxin
and ethylene are two of the most important of these
growth-regulating hormones.
Scientists had previously established that plants respond
differently to ethylene depending upon the type of plant tissue
it is applied to, the developmental stage of the plant, and the
surrounding environmental conditions. They also knew that the
presence of auxin, another key growth-regulator, often served as
a "trigger" for a plant to produce more ethylene, but were
unsure of the ways in which auxin was synthesized.
"Auxin controls almost every process in a plant," Alonso says,
"and so it's very important to understand how and why auxin is
produced within the plant."
In order to find out more about how auxin production is
triggered, the NC State team identified a mutant strain of
Arabidopsis - or mustard weed - that had a root system
insensitive to the growth inhibitory effect of ethylene.
When the team looked at the genome of this mutant strain of
mustard weed, they discovered that its lack of response to
ethylene was due to the changes in a gene that they named TAA1.
This gene produces a protein that is necessary for auxin
synthesis. In a normal plant, the TAA1 gene recognizes the
presence of ethylene as its signal to make proteins that in turn
synthesize auxin, which controls growth.
The researchers found that if the TAA1 gene and two other
related genes were "knocked out" or inactive, the plant had 50
percent less auxin than normal.
Their findings are the first to definitively establish a
relationship between a particular family of genes,
tissue-specific ethylene response, and auxin production in
plants.
"If we want to do intelligent manipulation of plants, to breed
them so that they ripen at a certain rate, or so that they're
well-adapted to particular environments, then we need to
understand more about the ways that these hormones interact or
'talk' to each other," Alonso says. "This research gives us
concrete evidence for at least one way in which this happens." |
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