UF Developing Genetic Pesticides
Each year in the United States, termites gnaw away more than $1 billion in structural damage despite an ever growing array of insect control techniques. In the search for control of the pest, the next generation of weapons could target the termite’s own genes. “The trend in insect control is to find methods that eliminate the problematic insect without affecting anything else in the environment, said Michael Scharf, an entomologist with the University of Florida’s Institute of Food and Agricultural Sciences. “What could possibly be more specific than genes that are unique to the insect itself?”
In a paper published recently online in the journal Insect Biochemistry and Molecular Biology, Scharf, along with colleagues Xuguo Zhou, Faith Oi and graduate student Marsha Wheeler, describes the effects of a mixture that, when consumed by termites, causes them to be cripplingly deformed after molting. The active agent in this “genetic pesticide” is RNA - small strips of genetic material that, within a cell, carry the instructions encoded in DNA to other cellular structures that put those instructions to work.
The team analyzed part of the termite genome and picked a gene that would disrupt the insect’s life cycle and is only found in that type of termite. They then crafted an RNA structure that would interfere with the RNA associated with that specific gene - thus silencing its activity. “For a long time, the pest control industry has been trying to develop neurotoxin-like chemicals to control insects by trying to tailor the toxin to the insect,” said John Reese, a Kansas State University entomology professor working on a genetic pesticide for aphids. “But all nervous systems are going to be at least a little bit alike, and the chances that you could hurt other creatures or cause damaging pollution are still a major concern. But if you try to interfere with a gene of an insect, there’s virtually no chance that you’re going to affect a mammal and almost no chance that you’ll even affect an insect that’s a close relative to the target species,” Reese added.
RNA interference techniques are being used at genetic research institutions across the nation. They are typically used to discover what a gene does in an organism by “silencing” it and seeing what happens. However, even using sophisticated laboratory techniques, it is difficult to effectively introduce foreign RNA into a mammal’s body, said David Root, project leader of the RNA Interference Consortium at the Broad Institute of the Massachusetts Institute of Technology and Harvard University. However, certain lower life forms seem to be able to absorb RNA by simply consuming it. “We can soak a worm in an RNA mix, and it will have an effect,” Root said. “But even our best lab tricks aren’t completely reliable at getting RNA interference to work in a mouse. And humans are way more complex than mice.”
Despite certain pests’ susceptibility to RNA interference, any marketable genetic pesticide is still many years away from development, Scharf said. When and if they are put into use, however, they may solve another major problem associated with insecticide use - resistance. Insects tend to build resistance to toxins that affect their nervous system. The type of changes required to adapt to genetic pesticides would be much more difficult for pests to overcome. And even if they did, there are thousands of genes within an insect’s genome that could be similarly targeted. In the case of the termite, there is much interest by the U.S. Department of Energy to sequence the insect’s entire genome to shed light on biological processes that could help researchers find ways to break down woody cellulosic materials into alternative fuels such as ethanol. (University of Florida News, 5/28/08).
