New designer toxins kill Bt-resistant in...( A new way to combat resistant pests ...)

A new way to combat resistant pests stems from discovering how the widely used natural insecticide Bt kills insects.

Figuring out how Bt toxins punch holes in the cells of an insect's gut was the key to designing the new toxins, according to a Mexico-U.S. research team.

Some insects have developed resistance to Bt toxins, naturally occurring insecticides used worldwide to combat pests of crops such as cotton and corn and also disease-carrying mosquitoes.

"This is the first time that knowledge of how Bt toxins work and how insects become resistant have been used to design toxins that kill resistant insects," said research team member Bruce Tabashnik of The University of Arizona in Tucson.

The discovery is important for cotton-growing areas such as northern Mexico, Texas and Arizona. More than 90 percent of Arizona's approximately 200,000 acres of cotton are planted in the biotech cotton known as Bt cotton.

"Our goal is to control insects in environmentally friendly ways so we can limit the damage that insects do to crops and the harm they do to people by transmitting disease," said Tabashnik, head of the UA's entomology department and a member of the UA's BIO5 Institute.

"Bt toxins are great for that because they only kill certain insects and don't harm other living things. These new designer toxins give us another environmentally friendly way to control insects."

The Mexico team developed the designer toxins by tweaking the gene that codes for the toxin, a protein. The researchers then teamed up with Tabashnik to test their modified toxins on UA's colony of Bt-resistant pink bollworms, major cotton pests.

Team member Alejandra Bravo, a research scientist at Universidad Nacional Autonma de Mxico (UNAM) said, "We proposed that changing a small part of the toxin would kill the insect -- and we did it."

The team's research article, "Engineering Modified Bt Toxins to Counter I
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