The next generation of pesticides

BROOKINGS, S.D. -- Every year, the fate of the entomological world is discussed by nearly 3,000 entomologists at the annual meeting of the Entomological Society of America (EntSoc).

BROOKINGS, S.D. -- Every year, the fate of the entomological world is discussed by nearly 3,000 entomologists at the annual meeting of the Entomological Society of America (EntSoc).

This year, the event was held in Knoxville, Tenn. Often, a hot topic is clearly identifiable from this meeting. This year is no exception, says Jonathan Lundgren, research entomologist with the U.S. Department of Agriculture's Agricultural Research Service North Central Agricultural Research Laboratory in Brookings, S.D. Lundgren says the major theme of the meeting was the next generation of insecticides, which are RNAi-based.

He explains that interference RNA, or RNAi, is the name given when a cell wants to make a protein and activates a particular gene. When the cell wants to stop making a protein, it turns the gene off using various methods. One way cells turn a gene off is by sending in a small fragment of RNA that suppresses the gene's expression into a protein. This process is called RNA interference, or RNAi.

"The implications of RNAi (which was discovered 15 years ago) are enormous," Lundgren says. "Just by knowing the DNA sequence of a gene, researchers can cheaply create a small molecule of RNA and send it into a cell to block protein production by the gene -- functionally turning the gene off."

By flipping a gene off and watching, he says we can figure out what each gene does. If we know the DNA sequence that produces diseases such as cancer, it may be possible to turn off the offending genes molecuar crotch. These two uses of RNAi are called functional genomics and gene therapy.


Multiple uses

Scientists are interested in using RNAi for all sorts of things, including to silence critical gene function in insect pests, thereby killing them.

"The eddy of this concept has turned into a tidal wave, and 78 presentations at the EntSoc meeting this year pertained to using RNAi in insect research and control," he says. "Arguably, seed companies are a driving force in this discussion."

Seed companies have created a genetically modified corn plant that produces small RNAs that silence a gene in the western corn rootworm, the most costly pest of agriculture in the world. Efforts are under way to develop RNAi sprays that can be applied to households or the environment to kill pests.

"The instant question that comes to most people's minds is likely '... Is this safe?' All indications are that RNAi can be very specific to the target gene. We eat small RNAs with every meal, and to our knowledge it doesn't seem to hurt us," he says. "However, nearly all previous work on RNAi has been relegated to individual cells in a Petri dish, or to individual organisms (e.g. a sick grandma). Genetically modified crops are currently planted on nearly 10 percent of the terrestrial land surface of the United States. If RNAi-based pesticidal crops are planted on a similar scale, then this is an environmental exposure that is orders of magnitude greater than anything we have experienced before."

Lundgren says whether you love the idea of this new technology or hate it, the proliferation of this next generation of insecticides seems likely to be a part of our lives in the very near future.

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