Crops That Shut Down Pests' Genes

Continued from page 1

In addition to killing nonpest insects, Mathey-Prevot says, the gene-silencing mechanism could spread between different species of plant, or from plants to other organisms, such as bacteria in the soil. Such spread might be harmless, but then again, it might not. "We need to understand it a little bit more," Mathey-Prevot says.

Vaughn says that the research is in its early stages and that Monsanto has not set a timeline for bringing gene-silencing crops to the market. Monsanto will put its new transgenic corn "through a battery of tests" to establish that its effects are specific to corn rootworms, he says. Tobacco cutworms that ingested the corn did not seem to be affected.

But to prove conclusive, researchers say, such testing would have to be arduous. "You would have to anticipate all the species you wouldn't want it to affect" and then test them, says David Root, project leader of the RNA Interference Consortium at the Broad Institute, Harvard and MIT's jointly operated center for research on genomic medicine. And Gordon anticipates that regulatory agencies will demand broad screening.

Although humans have genes similar to insect genes, researchers say that it is highly unlikely that ingesting Monsanto's corn would cause gene silencing in people. "If you fed tons of it to a mouse, I don't think you'd get anywhere," says Root. RNA "just gets digested" by mice and humans.

The U.S. government does not require the labeling of foods containing genetically modified organisms, but it does require safety testing. Fred Gould, professor of agriculture at North Carolina State University, says that because the new crops produce what's effectively a pesticide, they would be regulated by the U.S. Environmental Protection Agency. Such foods must be tested both in animals and through exposure to what Gould calls "reconstituted human stomach juices."

It's also unclear how widely applicable the use of RNA interference as a pesticide will be. In many insects, ingestion of RNA may not cause gene silencing. But cotton bollworms and corn rootworms are major agricultural pests, feeding on two of the most widely grown crops in the world. Even if RNA interference is helpless against any other insects, it could still have a major impact on agriculture.

Mathey-Prevot counsels patience. At this point, he says, it's too early to make claims about the safety of the technique. But, he says, that also means it's too early to conclude that the ability to cause RNA interference is any more dangerous than current genetic modifications of food crops.