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Comments on Audrey Bellier et al. (2008) C.elegans Aging, Stress, Pathogenesis, and Heterochrony Meeting "Mutation confers resistance to Bacillus thuringiensis Cry toxins in C. elegans" (0)
Overview
Audrey Bellier, Chang-Shi Chen, & Raffi Aroian (2008). Mutation confers resistance to Bacillus thuringiensis Cry toxins in C. elegans presented in C.elegans Aging, Stress, Pathogenesis, and Heterochrony Meeting. Unpublished information; cite only with author permission.
Crystal (Cry) proteins made by the bacterium Bacillus thuringiensis (Bt) are pore-forming toxins that specifically target insects and nematodes. To better understand the toxicity of the Cry toxin and the resistance pathways of the target animals, we are studying Bt toxin action and resistance in C. elegans. A previous genetic screen in the laboratory for C. elegans resistance mutants to Cry5B intoxication led to the identification of glycolipid carbohydrates as key receptors for Cry5B toxin. We have been studying another Cry toxin -Cry21A- that is also highly toxic to C. elegans. Interestingly, the mutants resistant to Cry5B appear to be sensitive to Cry21A, suggesting that Cry5B and Cry21A proteins use different receptors or different mechanisms to intoxicate the nematodes. Thus, studying resistance to Cry21A is predicted to help elucidate new ways nematodes can use to resist Bt toxins. We have developed an efficient genetic screen for recovering mutants resistant to Cry21A. Those mutants appear with a much lower frequency than Cry5B resistant mutants, suggesting that Cry21A is harder to resist. One of the mutants found in that resistance screen presents an early stop codon in a previously identified gene. Loss-of-function mutation in this gene has already been reported to confer resistance to pathogenic attack. Interestingly, we found that this mutant is also resistant to other Cry toxins -Cry5B and Cry6A-, showing for the first time a broad resistance mechanism to different Cry toxins. Moreover, we found that this mutant shows resistance to various other stresses such as heat, pathogenic bacteria and has an increased lifespan. We will present here the first mutant resistant to Cry toxins that is not related to a Cry toxin specific mechanism (receptor, proteases..), but is a broadly applicable mechanism.