West Lafayette, Indiana
May 4, 2004
A Purdue
University research team has found a set of genes that may
orchestrate insects' ability to fight the effects of pesticides.
"Our study
suggests that more than one gene may be involved in making
insects resistant to certain pesticides," said Barry
Pittendrigh, associate professor of entomology. "Using a music
analogy, metabolic resistance may not be a single individual
playing a single instrument. It's more likely a symphony with
numerous instruments playing a role in producing the music."
The
ultimate aim of the research is to develop methods to prevent
insect damage to plants, he said. Results of the initial study
are published in the Tuesday (May 4) issue of Proceedings of the
National Academy of Sciences.
The
scientists looked at approximately 14,000 genes from both
metabolically resistant and non-resistant wild-type fruit flies.
They identified dozens of genes that were different in resistant
fly lines compared to non-resistant wild-type flies, Pittendrigh
said. This indicates that a number of genes may be part of the
metabolic resistance-causing orchestra, he said.
In
metabolic resistance, an organism, in this case an insect,
breaks down a toxin that normally might be fatal. Organisms
metabolize the toxin or turn it into something that disables the
harmful molecules, and then dispose of it.
"We have
identified a series of genes that are interesting because the
high abundance, or expression, of their genetic traits in
resistant flies signifies they may be part of the orchestra that
leads to resistance," Pittendrigh said. "But more research must
be conducted before we claim whether any of these genes actually
cause resistance.
"Another
interesting finding that emerged from our study is that a series
of genes are common to both resistant insects found in the field
and those used in the laboratory. Hypothetically, this could
lead to common genes that consistently have the same resistance
traits across fly lines or even potentially across insect
species."
If further
research proves this to be true, these genes might be tools for
controlling many different insects, he said.
Joao Pedra,
an entomology doctoral student and lead author of the paper,
said data from the study suggest that more than one
detoxification gene is over-expressed in resistant insects.
"Different
resistant fly lines also may have different levels of expression
of these genes," Pedra said. "This may affect how resistant they
are to a pesticide."
Knowing
genes involved in resistance and their relationship to each
other would provide scientists with information needed to
develop ways to halt insects' detoxification of chemicals
designed to kill them.
"It would
be great if we would ultimately identify a 'conductor' gene that
is critical for directing the biochemical processes that allow
insects to detoxify pesticides," Pittendrigh said. "A gene or
genes that may be critical for resistance, in turn, may become
targets, enabling us to develop compounds to control
pesticide-resistant insects."
The
scientists already have found that some of the genes they're
studying are involved in the process of metabolizing some
pesticides, rendering them ineffective.
"We have a
relatively firm grasp of target insensitivity - when a toxin
will no longer bind with a molecule in an insect so the chemical
no longer kills the insect," he said. "But to date, we still
don't understand many aspects of metabolic pesticide resistance.
"Finding
genes involved in the fundamental resistance process that also
are found across insect species may provide for better
resistance monitoring or even resistance management strategies."
One type of
bug, the tarnished plant bug, includes two species native to the
United States that cause moderate to severe damage to fruits,
vegetables, tree seedlings, cotton and alfalfa. The total annual
losses and control costs attributed to this one insect are $2.1
billion to $3.5 billion, according to the U.S. Department of
Agriculture's Agricultural Research Service.
Pittendrigh's team used a recently developed technology to
simultaneously look at all the genes in a common research
animal, the fruit fly (Drosophila). The technology, high-density
micro-array analysis, makes it possible to scan the insect
genome and record differences between resistant and susceptible
insects.
"Understanding the gene or genes that conduct the metabolic
resistance orchestra would give us a way to soften the crescendo
of insect damage," Pittendrigh said.
The other
researchers involved with this study are: Lauren McIntyre,
associate professor in the Department of Agronomy and a member
of the Purdue Genomics Center Micro-Array Core Facility, and
Michael Scharf, an entomology research specialist, director of
the Industrial Affiliates Program and a member of the
Purdue Center for Urban and Industrial Pest Management.
Pittendrigh and Pedra also are members of the Purdue Molecular
Plant Resistance and Nematode Team.
The
National Institutes of Health, U.S. Department of
Agriculture, Purdue Research Foundation and
Department of Entomology provided funds for this study.
Writer:
Susan A. Steeves, (765) 496-7481,
ssteeves@purdue.edu
Sources: Barry
Pittendrigh, (765) 494-7730,
pittendrigh@purdue.edu / Joao Pedra, (765) 494-6313,
jpedra1@purdue.edu |