Insecticides To Target Insect Life Cycle

Because the pesticides attack insect juvenile hormone, which has no equivalent in higher animals, they will be harmless to vertebrate animals and humans, says Australia's largest public research institution, CSIRO.

The research team of scientists from CSIRO and the US has cloned two proteins which regulate the level of insect juvenile hormone.

"The level of this hormone is crucial in development where it controls the process of metamorphosis," says Dr Tony Zera of the University of Nebraska.

"In insects such as locusts juvenile hormone is also one of the factors that controls the switch between their sedentary stage and their migratory stage. In the flight stage of their life cycle they are a moving target and much harder to control.

"This new technology is an example of the power of collaborative science," he says. "The opportunity to develop a potentially valuable class of chemical insecticide has been created by combining the skills of CSIRO Entomology in cloning technologies with our work on insect development and biochemistry in the US."

Two key proteins called juvenile hormone esterase (JHE) and juvenile hormone binding protein (JHBP) control the level of juvenile hormone. This in turn regulates the passage of juvenile insects through their various moults to become adults.

"In many insects which have different adult forms specialised for different functions, the hormone also determines which of these adult forms they become," says Dr Zera.

"Alterations to JHE and JHBP disrupt development and in the case of insects like crickets and grasshoppers can prevent commencement of the migratory phase.

"The important step from the point of view of commercial application has been the cloning of JHE and JHBP in CSIRO Entomology's biotechnology program," says Dr Zera. "This means that we can now apply for patents for the use of these genes in the search for new, safer chemical insecticides."

Dr John Oakeshott, leader of CSIRO Entomology's biotechnology program, says that his research team has cloned the genes producing JHE and JHBP from several different insects.

"We can now format these proteins in high speed screening systems to scan libraries of natural and synthetic chemicals for molecules that would disrupt the function of the proteins and give us new candidates for chemical insecticides," he says.

Dr Zera, who is visiting CSIRO Entomology this month, is supported by the US National Science Foundation and CSIRO's research is supported by the Cotton Research and Development Corporation.