Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2009
Publication Date: 7/1/2009
Publication URL: http://doi:10.1016/j.jinsphys.2009.05.001
Citation: Liu, C., Wu, K., Wu, Y., Gao, Y., Ning, C., Oppert, B.S. 2009. Reduction of Bacillus thuringiensis Cry1Ac Toxicity Against Helicoverpa armigera by a Soluble Toxin-Binding Cadherin Fragment. Journal of Insect Physiology 55:686-693. Interpretive Summary: The cotton bollworm is effectively controlled by Bacillus thuringiensis (Bt) transgenic plants. Managing insect resistance to the microbial toxins requires a thorough understanding of the gut molecules that interact with the toxin. A portion of the Bt toxin binding protein in the bollworm was cloned, and it was demonstrated that this protein fragment could reduce toxicity and inhibit binding of the toxin to midgut cells. These data can be used by scientists in developing bollworm resistance management strategies.
Technical Abstract: A cadherin-like protein has been identified as a putative receptor for Bacillus thuringiensis (Bt) Cry1Ac toxin in Helicoverpa armigera and plays a key role in Bt insecticidal action. In this study, we produced a fragment from this H. armigera Cry1Ac toxin-binding cadherin that included the predicted toxin binding region. The cadherin fragment was evaluated for its effect on Cry1Ac toxin-binding and toxicity, analyzed by ligand blotting, binding assays, and bioassays. The results of ligand blotting and binding assays revealed that the binding of Cry1Ac to H. armigera midgut epithelial cells was inhibited under denaturing or native conditions in vitro. Bioassay results indicated that toxicities from Cry1Ac protoxin or activated toxin were neutralized in vivo by the H. armigera cadherin fragment. These results are discussed relative to conflicting reports that cadherin fragments can enhance the activity of Bt toxins.