Cloning Genes That Confer Resistance to Bacillus thuringiensis Toxin

University Of California-San Diego, La Jolla CA

Investigators

Abstract

The goal of this project is to study the toxicity and resistance to the endotoxins produced by the bacterium Bacillus thuringiensis (Bt) in the nematode, Caenorhabditis elegans. Ten mutations in five different genes that confer marked resistance to the Bt toxin Cry5B, a member of the main family of Bt toxins, have been isolated. These five Bt resistant (bre) genes map to three chromosomes. The specific aims of this research are: 1) To clone the five bre genes that confer resistance to Bt toxin 2) To characterize the pathway(s) that gives rise to resistance 3) To determine what elements in the pathway are common to different Bt toxins and what elements in the pathway are unique to different Bt toxins 4) To determine whether bre genes might be involved in Bt toxicity and resistance in parasitic nematodes. Endotoxins produced by B. thuringiensis are the most important and prevalent biologically produced pesticides in use today. Bt toxins act on invertebrates by damaging and destroying their intestinal cells. Despite decades of use of Bt toxins as insecticides and the recent introduction of Bt toxin genes in transgenic plants, very little is known about the molecular host components required by Bt toxicity and no genes that confer resistance to Bt toxins have yet been cloned. There are growing concerns about the development of resistance to Bt toxins and about the effects of Bt toxins on non-pest species. These concerns increase the urgency for understanding the molecular mechanisms for Bt toxin action.