such as "Introduction", "Conclusion"..etc
Breakthrough research done earlier this year by a plant cell biologist
at the University of California, Riverside has greatly accelerated
scientists' knowledge on how plants and crops can survive difficult
environmental conditions such as drought.
Working on abscisic acid (ABA), a stress hormone produced naturally
by plants, Sean Cutler's laboratory showed in April 2009 how ABA helps
plants survive by inhibiting their growth in times when water is
unavailable -- research that has important agricultural implications.
The Cutler lab, with contributions from a team of international
leaders in the field, showed that in drought conditions certain receptor
proteins in plants perceive ABA, causing them to inhibit an enzyme
called a phosphatase. The receptor protein is at the top of a signaling
pathway in plants, functioning like a boss relaying orders to the team
below that then executes particular decisions in the cell.
Now recent published studies show how those orders are relayed at the
molecular level. ABA first binds to the receptor proteins. Like a
series of standing dominoes that begins to knock over, this then alters
signaling enzymes that, in turn, activate other proteins resulting,
eventually, in the halting of plant growth and activation of other
"I believe Sean's discovery is the most significant finding in plant
biology this year and will have profound effects on agriculture
worldwide," said Natasha Raikhel, the director of UC Riverside's Center
for Plant Cell Biology, of which Cutler is a member. "Because the ABA
receptor is so fundamentally important for understanding how plants
perceive various environmental stresses, I am sure the strings of
research that Sean's discovery sparks will be endless."
In only months since Cutler's discovery, six research papers in
journals such as Science and Nature have been
published that build on his work, a testament to the interest among
plant scientists to nail down how exactly the stress signaling pathway
works in plants. This intense activity in the field was expedited by
Cutler's willingness to share information with colleagues before his own
research was published -- an open approach that is at odds with the
often cutthroat competition in hot scientific areas.
"This intense interest by the scientific community will certainly
accelerate the development of new agrichemicals that can be used to
control stress responses in crops, and I believe we need to work openly
to tackle problems of such great importance," said Cutler, an assistant
professor of plant cell biology in the Department of Botany and Plant
Sciences. "There is also tremendous interest from industry, and we are
moving closer to designing both improved chemicals that can control
drought tolerance in crops and improved receptor proteins that can be
used to enhance yield under drought conditions. Ultimately, my vision is
to combine protein and chemical design to usher in a fundamentally new
approach to crop protection. These recent papers are an important step
towards realizing that goal."
Determining how the chemical switch works
One of the six research papers that builds on Cutler's work is
published online Nov. 18 in Nature. The research, led by
Jian-Kang Zhu, a professor of plant cell biology at UCR, fleshes out the
domino pathway from the receptor down to the proteins that control
"Freshwater is a precious commodity in agriculture," Zhu said.
"Drought stress occurs when there is not enough freshwater. We wanted to
understand how plants cope with drought stress at the molecular level.
Such an understanding is necessary if we want to improve the drought
tolerance of crop plants through either genetic engineering or
In their Nature paper, Zhu and his colleagues report on how
they reconstituted in a test tube the process of information transfer
from receptor to phosphatase, and all the way downstream to the protein
that turns the gene on or off, and then ultimately to the gene itself.
"The ABA signaling pathway we reconstituted is arguably the most
important pathway for plants to cope with drought stress." Zhu said.
"This is the first time the whole pathway has been reconstituted in
vitro. What is emerging is a clear picture of how the chemical
switch works -- useful knowledge for designing improved chemical agents
for application in crop fields."
Zhu explained that in vivo studies (done in the living body
of the plant) involve thousands of proteins, which can complicate data
interpretation. By doing the study in vitro (outside the living
body of the plant) his lab avoids this problem, making it possible to
determine the minimal number of components necessary and sufficient for
the ABA response pathway.
Next in its research, the Zhu lab will use the knowledge of the ABA
response pathway to make transgenic plants that will have substantially
higher levels of drought tolerance, achieved by manipulating the levels
and activities of the key components of the pathway. The lab also plans
to investigate how drought stress triggers the production of ABA.
Zhu was joined in the research by Cutler and UCR's Hiroaki Fujii,
Viswanathan Chinnusamy, and Sang-Youl Park. Americo Rodrigues, Silvia
Rubio, Regina Antoni and Pedro L. Rodriguez of the Instituto de Biología
Molecular y Celular de Plantas, Spain; and Jen Sheen of the
Massachusetts General Hospital also collaborated on the study.
Zhu was funded by a grant from the National Institutes of Health.
Currently, he has an appointment also at the King Abdullah University of
Science and Technology, Saudi Arabia.
The other five research papers that Cutler's research inspired
discuss the molecular structure of the ABA receptor, showing in atomic
detail how ABA functions to trigger signaling.
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