SAN FRANCISCO -- Cornell University researchers have taken a first step in developing safe and effective birth control for America's number-one household pest, the cockroach. The entomologists say they have identified and cloned a key gene in the reproductive system of the male cockroach.
Success in cloning five P450 genes from the German cockroach was announced by Zhimou Wen today (March 28) at the national meeting of the American Chemical Society (ACS) at the Moscone Convention Center, in San Francisco. Wen is a graduate student working in the laboratory of Jeffrey G. Scott, professor of entomology in Cornell's College of Agriculture and Life Sciences.
"Cockroaches - specifically, the brown-banded and the German cockroaches - are the number-one urban household pest in terms of frequency," Scott explained in an interview before the ACS meeting. "They are the target of tons of neurotoxin pesticides every year but they keep coming back for more. What we really need is an effective, nontoxic treatment - a birth-control method - to reduce cockroach populations without bothering other insects or humans, either."
Scott admitted surprise that one of the genes - named CYP6L1 - has a reproductive function, although exactly what that function is remains uncertain. The entomology professor and graduate student have been studying German cockroach (Blattella germanica) genes in the P450 "superfamily" of genes, Scott said, noting that virtually all living organisms - from bacteria to plants to mammals, including humans - have P450 genes and their functions are not well understood. The two researchers were the first to clone P450 genes from the cockroach, then tried to learn at which stage of the insect's development the genes are "expressed." This, in turn, could lead to the identification of specific proteins with definite metabolic functions.
Initially their tests showed that CYP6L1 was expressed in adult cockroaches, while subsequent tests found the gene expression only in male adults, and finally, only in the male cockroach's testes and accessory glands.
"In other words, this gene is adult-male-reproductive-tissue-specific," Scott said. "We still don't know what hormone this gene is regulating, but this is enough of a clue to get us started. We're pretty sure the hormone is essential for reproduction. If we can knock out the CYP6L1 protein, we can make the pest struggle to reproduce."
The entomologists don't plan to tinker with the cockroach genes, Scott said. Rather, their strategy is to identify the hormone or other protein that is produced by expression of the insect's P450 gene, and then develop chemical inhibitors of the proteins that would be included in roach bait.
"Don't expect roach birth control on your store shelves tomorrow," Scott cautioned. "We probably have several years' work ahead of us." For one thing, the entomologist observed, the cockroach is a much more complex organism, genetically speaking, than the thoroughly studied fruit fly.
But the gene-based approach to pest control will be worth the effort, Scott said, if the result is a pesticide that afflicts only the specific pest and not other insects and even animals. One of the first tasks, he said, will be to learn if the P450 genes in the other common roach, the brown-banded cockroach, also are expressed only in the male reproductive tissue.
In the meantime, the household cockroach is in no danger of extinction and researchers have plenty of experimental subjects. The last time Scott and Wen needed cockroaches, they went to some old Cornell graduate-student housing units that were slated for demolition. There they found both the brown-banded and German types.
The Cornell study of cockroach genes was supported by the U.S. Department of Agriculture's Hatch funds and by a grant from Sigma Xi, the scientific honorary society.
Related World Wide Web sites: The following sites provide additional information on this news release. Some might not be part of the Cornell University community, and Cornell has no control over their content or availability.
-- Cornell Entomology Dept.: http://www.cals.cornell.edu/dept/entom/default.htm
-- University of Florida cockroach art and info: http://edis.ifas.ufl.edu/IG082
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