title: Engineering modified Bt toxins to counter insect resistance.
abstract: The evolution of insect resistance threatens the effectiveness of Bacillus thuringiensis (Bt) toxins that are widely used in sprays and transgenic crops. Resistance to Bt toxins in some insects is linked with mutations that disrupt a toxin-binding cadherin protein. We show that susceptibility to the Bt toxin Cry1Ab was reduced by cadherin gene silencing with RNA interference in Manduca sexta, confirming cadherin's role in Bt toxicity. Native Cry1A toxins required cadherin to form oligomers, but modified Cry1A toxins lacking one alpha-helix did not. The modified toxins killed cadherin-silenced M. sexta and Bt-resistant Pectinophora gossypiella that had cadherin deletion mutations. Our findings suggest that cadherin promotes Bt toxicity by facilitating toxin oligomerization and demonstrate that the modified Bt toxins may be useful against pests resistant to standard Bt toxins.
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, Cuernavaca 62250, Morelos, Mexico. mario@ibt.unam.mx
authors.forename: Mario
authors.initials: M
authors.lastname: Soberón
authors.forename: Liliana
authors.initials: L
authors.lastname: Pardo-López
authors.forename: Idalia
authors.initials: I
authors.lastname: López
authors.forename: Isabel
authors.initials: I
authors.lastname: Gómez
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Tabashnik
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bravo
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000633:toxicity*; D001427:Bacterial Toxins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000633:toxicity*; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D004731:Endotoxins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000633:toxicity*; D005818:Genetic Engineering; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000633:toxicity*; D007305:Insecticide Resistance; D007814:Larva; D018402:Manduca / Q000235:genetics / Q000378:metabolism; D009036:Moths / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010572:Pest Control, Biological; D034622:RNA Interference
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D015820:Cadherins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis