The University Record, January 21, 1998

Natural pesticide could safely prevent crop damage

By Randy Frank
U-M-Dearborn

When crops are sprayed with insecticides, fears arise about the harmful effects of chemicals to the environment and to humans.

John Thomas, U-M-Dearborn assistant professor of biology and genetics, and his associate, Italian chemist Luca Mezzo, hope to eliminate some concerns about insecticides through use of an egg-killing protein.

"We are developing a bio-pesticide that will kill insect eggs on the leaves of plants without harming the plant, environment or humans," Thomas says. "The bio-pesticide is chitinase, a protein able to dissolve the egg shells of most insects."

"Once we engineer the plants to produce the chitinase," Mezzo explains, "it will dissolve the insect eggs on the leaves, and if any chitinase remains, it will decompose naturally without hurting the environment."

The natural pesticide also is selective, Thomas says, meaning it will not destroy "good insects" such as bees, which are important to the growth of many plants.

"Even with the extensive use of plant breeding, chemical pesticides, pheromones, insect parasites and modified crop cultivation practices, insects annually damage millions of dollars worth of crops," Thomas says. "Mezzo and I think the safest and least expensive way to control insect pests is to combine traditional strategies with molecular methods to introduce and produce anti-insect products in transgenic plants."

When the chitinase is moved into a plant, the result is known as a transgenic plant.

Thomas and Mezzo currently are involved in the first phase of the project, using E. coli bacteria to produce the chitinase protein or enzyme. The E. coli bacteria is used because it is easy to grow and is used in other cloning and molecular applications in the laboratory, Thomas explains. "E. coli is a protein factory that is a safe and inexpensive method to use."

In the next step, the chitinase is purified through "affinity chromatography," in which it binds with beads of resin that are released in a chemical solution and the extraneous molecules are removed. The purified chitinase is then introduced into dishes that contain fruit-fly eggs.

"We want to see how active this enzyme is before starting the second phase of investigation, which would involve introducing chitinase production in tobacco and petunia plants," Thomas says.

If the process works in tobacco and petunia plants, the two scientists will test it in cotton plants, where 60 to 70 percent of chemical insecticides (by weight) are used in the United States.