38th Annual Meeting of the Society for Invertebrate Pathology

Bacillus thuringiensis Cry1A proteins exerts their toxic effect through a receptor-mediated process, involving both cadherin and aminopeptidases. Both of these proteins have been identified in a number of insects including Heliothis virescens and Manduca sexta. Disruption of both cadherin and aminopeptidase affects Cry1A toxicity. In a recently reported study we show that the Cry1A toxin-binding region in H. virescens cadherin-like protein was mapped to a 40-amino acid fragment, from aa 1422 to 1461. Mutations in this region, to which the Cry1A binds through its loop 3, resulted in the loss of toxin binding. Further, feeding of the anti-H. virescens cadherin antiserum or the partial cadherin-like proteins, which contain the toxin binding region, in combination with Cry1A alleviated insect mortality, showing this region is involved in insect toxicity. Immunohistochemistry showed the cadherin-like proteins are present in the insect midgut apical membrane, which is the target site of Cry toxins. This subcellular localization is distinct from that of classical cadherins, which are usually present in cell-cell junctions.