East Lansing, Michigan
July 19, 2007
The mystery of how a major plant
hormone works to defend plants against invaders has been
revealed, thanks to collaborative research efforts by
Michigan State University and
Washington State University.
While scientists have known for years that a common plant
hormone, jasmonate, plays a crucial role in plant development
and function, the steps that convert the hormone’s signal into
genetic and cellular action have remained elusive. MSU
scientists Sheng Yang He and Gregg Howe were part of two
back-to-back discoveries that solved the mystery, described in
the July 18 online issue of the journal Nature.
Jasmonate is the last major plant hormone to have its signaling
process revealed. Initial research by WSU researchers identified
the family of proteins – dubbed JAZ proteins – that are critical
to plants receiving and responding to the jasmonate signal.
“In a healthy environment, these JAZ proteins are doing their
job – they’re blocking all the defenses and signals, because
they are not needed,” said Howe, an MSU professor of
biochemistry and molecular biology. “But when a plant becomes
stressed by an insect or pathogen, the plant needs to respond
very quickly if it’s going to be successful in warding off the
attacker.”
Independent of the WSU work, Howe and He used Arabidopsis, a
common lab plant, and tomato plants to determine how the JAZ
proteins work. Their experiments showed that the jasmonate
signal causes direct interaction between JAZ proteins and a
second protein complex, SCFCOI1, that works to eliminate the JAZ
protein so that the plant can mount a defense response.
Based on the research findings, there is strong evidence to
suggest that Howe and He might have identified the SCFCOI1
protein complex as the receptor for jasmonate.
“We found that when jasmonate is present the COI1 and JAZ
proteins bind together,” said He, an MSU professor of plant
biology, plant pathology, and microbiology and molecular
genetics. “This opens the way for the plant to turn on the
necessary genetic or cellular response.”
As part of their research, Howe and He have proposed a model for
how this interaction works.
“Now that we know what the active signals are and have
identified the key regulatory proteins – the JAZ proteins –
involved, the hope is to either genetically modify plants or
develop compounds that mimic the jasmonate hormone,” Howe said.
“The research may help scientists engineer plants for increased
resistance to insects and pathogens.”
Researchers at both universities will continue to work on other
critical aspects of this research.
“Understanding how the jasmonate system works will shed light on
all the processes in which the hormone is involved, notably
plant reproduction and defense,” said John Browse, head of the
WSU Institute of Biological Chemistry research team.
“This study represents a significant advance in our
understanding of a major plant hormone and how it works,” He
said. “We are excited to be part of this collaborative effort
and look forward to extending the understanding and application
of this important work.”
The research was funded by the National Institutes of Health and
the U.S. Department of Energy and supported by the Michigan
Agricultural Experiment Station.
A copy of the Nature article is available at
http://www.nature.com/nature/journal/vaop/ncurrent/index.html.
Michigan State University has been advancing knowledge and
transforming lives through innovative teaching, research and
outreach for more than 150 years. MSU is known internationally
as a major public university with global reach and extraordinary
impact. Its 17 degree-granting colleges attract scholars
worldwide who are interested in combining education with
practical problem solving.
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