New Plant-Insect Interaction Discovered
August 15, 2007
A new class of compounds has been
discovered that should help shed more light on how plants respond to insect
attacks. Agricultural Research Service (ARS) scientists with the Center for Medical,
Agricultural and Veterinary Entomology (CMAVE)
in Gainesville, Fla., along with colleagues at the
Virginia Military Institute
and the Pennsylvania State University,
isolated the compounds from oral secretions of Schistocerca americana
grasshoppers fed corn seedlings.
Plants, and the insects that feed on them, engage in a relationship
involving many resultant hormonal and chemical changes in the plant, including
induced production and emission of volatile organic compounds, or VOCs. These
physiological changes, brought about by a group of compounds known as
elicitors, varynot only for different plants, but also with the insect
species feeding on a plant. Understanding the plant- insect interaction is
important in crop science and insect pest management.
T. Alborn, in CMAVE's
Research Unit, led the team that isolated the previously unidentified class
of compounds. They named them caeliferins because preliminary analyses of oral
secretions collected from several species of Orthoptera (grasshoppers, katydids
and crickets) indicated that the compounds may be present in most, if not all,
grasshoppersmembers of the suborder Caeliferabut not in crickets or
katydids in the suborder Ensifera.
The caeliferins that Alborn isolated have some unique properties, so they
should provide new biological tools and directions for exploring the
physiological ecology of, and interactions between, insects and plants.
Interestingly, the pattern of caeliferins may determine whether S.
americana grasshoppers are solitary or gregarious. If so, the compounds may
be found to influence swarming behavior of locusts.
The CMAVE scientists study elicitors of plant volatile releases to find ways
to induce defensive responses to help crop plants under insect attack remain
healthy and vigorous. Its well known that insect chewing may induce
release of plant VOCs that summon natural enemies of the attacking insects. But
insects oral secretions may also provoke direct plant defenses that
impair the pests performance.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.