Imagine being able to control the cockroaches in your house by turning up the thermostat 10 degrees while you're away for the afternoon. Or being able to wipe out corn borers by using a little fertilizer instead of a lot of pesticide.
For those scenarios to work, the insect pests themselves would have to become fatally susceptible to chemicals or conditions they previously shrugged off. They'd have to become new cockroaches or corn borers with built-in extra sensitivity to warmth or nitrogen.
Notre Dame researcher Malcolm J. Fraser Jr., is exploring ways to rebuild insect pests in this way using transgenic engineering, or borrowing a gene from one organism and installing it in another to produce a desired trait.
Fraser, an associate professor of biological sciences, has spent more than a decade studying movable genes, known as transposons, that he discovered in a crop-devouring caterpillar called the cabbage looper. A transposon is a piece of genetic material that moves around in the chromosomes of bacteria, plants and animals, including humans. These so-called "jumping genes" make copies of themselves as they move, thereby maintaining themselves as part of the genetic material of their host organism. Fraser found the cabbage looper transposon after it jumped into a gene of a virus that infects the cabbage looper.
Current methods of genetic manipulation used for biological control of insect pests rely on breeding huge colonies of the altered pest with the desired trait and then releasing them into the natural population. In principle, genetically altered pests will decrease the mating potential or viability of bugs they contact. But in many cases the traits they carry cannot be maintained in the population for more than a couple generations.
With transposons, once the new genetic material is installed into an organism, the natural tendency for the transposon to maintain itself forces all of the organism's progeny to carry the trait. Theoretically, a small number of transgenically altered insects could be released into a pest population and produce succeeding generations of pests with traits that make them easy to control.
Such traits might be extra sensitivity to a chemical pesticide or some other chemical supplied in, say, fertilizers. That way farmers could feed and de-bug in one treatment. Another idea might be to introduce into the pests' genetic makeup a fatal response to the elevated temperatures of a July field or an intentionally overheated kitchen.
Geneticists have studied the transposon from another insect, the fruit fly, for nearly two decades and now understand much about how jumping genes cause mutations when injected into fruit fly embryos. One problem with the fruit fly's transposon, however, is that it can't be installed in many other organisms yet. Fraser's cabbage looper transposon has already proven compatible with several other moths, he says.
The biologist cautions that years, if not decades, of research followed by regulatory approval likely lie ahead before transgenically engineered pests will be ready to be released into natural populations.