May 2004
Insecticide Resistance “Orchestra”
A Purdue University research team has found a set of genes that may orchestrate insects' ability to fight the effects of insecticides. "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. Published in the May 4th edition 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. This indicates that a number of genes may be part of the metabolic resistance-causing orchestra.
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."
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," Pedra 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.” (www.aganswers.net via Agnet, 5/4/04).
