INSECTICIDAL TOXINS FROM THE BACTERIUM PHOTORHABDUS-LUMINESCENS

Transgenic plants expressing Bacillus thuringiensis (Bt) toxins are cu rrently being deployed for insect control. In response to concerns abo ut Bt resistance, we investigated a toxin secreted by a different bact erium Photorhabdus luminescens, which lives in the gut of entomophagou s nematodes. In insects infected by the nematode, the bacteria are rel eased into the insect hemocoel; the insect dies and the nematodes and bacteria replicate in the cadaver. The toxin consists of a series of f our native complexes encoded by toxin complex loci tca, tcb, tcc, and tcd. Both tca and tcd encode complexes with high oral toxicity to Mand uca sexta and therefore they represent potential alternatives to Bt fo r transgenic deployment.