The tobacco hornworm, Manduca sexta, is an agricultural pest and a model insect for investigating Bacillus thuringiensis (Bt) Cry toxin mode-of-action. The cadherin-like protein Bt-R1 is a receptor of Cry1A toxins. In larvae, Bt-R1 is located on the external surface of the midgut epithelial cell membrane. The extracellular portion of Bt-R1 is composed of 12 tandemly repeated ectodomains (EC) and a membrane-proximal extracellular domain (MPED). In this research, we expressed fragments of the extracellular regions of Bt-R1 in Eschericia coli. Binding properties of these Bt-R1 truncations were tested using the ligand blot technique. Unexpectedly, two Cry1A binding regions were identified located in EC11 and EC12. These regions appear to function cooperatively as Cry1A binding regions as both regions are required for detection by Cry1A toxins on blots. Additional experiments are in progress to define the function of EC11 and EC12 regions in Bt toxin action in M. sexta.
Species 1: Lepidoptera Sphingidae Manduca sexta (tobacco hornworm)
Species 2: Bacillales Bacillaceae Bacillus thuringiensis
Keywords: receptor, cadherin
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