South Carolina
August 8, 2006
University of South Carolina (USC) researchers are seeking a
discovery that could help scientists develop new tomato
varieties with stronger defenses systems to battle the insects,
bacteria, fungi and viruses that threaten and destroy crops.
"Tomatoes are frequently attacked by a number of enemies -
insects and microbial pathogens alike. But they have a very
effective and sophisticated defense system that has evolved over
millions of years," said Dr. Johannes Stratmann, whose research
team includes USC undergraduate biology students Wayne Miller of
Greenville and Suchita Pancholi of Columbia.
"We are trying to understand these defense mechanisms at the
molecular level," said Stratmann, whose studies are funded by
the National Science Foundation. "Our research could help other
scientists develop new crop plants that are effective in
battling insects and other stressors. But before we can develop
better plants, we have to know how the plant works."
Stratmann likens the workings of the tomato plant's cellular
defense system to a radio, where waves are perceived by the
antenna and relayed to a transistor that amplifies the signal,
producing sound.
"We see a similar situation in a cell," said Stratmann. "When
tomato plants are attacked and wounded by plant-eating insects,
a small peptide (protein) called systemin is released at the
wound site."
At a target cell, the systemin interacts with a receptor, the
equivalent of the radio antenna. The systemin signal is then
amplified along a so-called "signal transduction pathway."
Ultimately, defense genes are activated. These genes encode
proteins that block digestive enzymes in the insects' guts. This
reduces the growth of the attacking insects, which begin to
starve or move on to other plants.
Miller is looking at a protein that functions in the signal
transduction pathway of systemin. To characterize the function
of this protein, he engineered a harmless plant virus that turns
off the gene that encodes the signaling protein. The assumption
is that when the gene is turned off, the signal transduction
should be interrupted and the defense response halted. This
would prove that the protein is essential for the defense
response.
"This technique is giving us an understanding of the signal
pathways involved in the plant's defense system," said Miller, a
senior who wants to continue graduate studies in plant biology.
"Our work on signaling genes is proving to be successful."
Pancholi, a South Carolina Honors College senior who hopes for a
career in research or medicine, is working on another signaling
protein, which is part of the systemin signaling pathway. She is
studying how this protein responds to wound signals that are
generated by insects at the wound site and travel to distant
parts of the plant.
These signals are very fast, with a speed of up to one inch per
second. It is thought that the signals prepare the entire plant
for an attack by an insect. Pancholi's work with Stratmann will
help provide clues for biotechnology on how to alter the
signaling pathways in crop plants to make them more resistant to
the stresses they encounter.
"This experience is a very important component of my education,"
she said. "You can't conduct research without knowing the basic
concepts of biology."
Pancholi and Miller, recipients of USC's Belser Award that
recognizes outstanding students in plant biology, are working
with Stratmann as part of USC's Magellan Scholars Program, which
enables undergraduate students to conduct research in the labs
of the university's top scientists.
Stratmann said it's important for the university to provide
research experiences for undergraduates.
"These students are producing valuable results," he said. "They
bring a fresh perspective to our research."
Miller, whose work will be part of a paper being submitted for
publication in a scientific journal, said, "I've been able to
apply what I've learned in the classroom to my research. It has
helped me to see the practical applications of what I'm
learning." |