title: Bacillus thuringiensis Cry1AbMod toxin counters tolerance associated with low cadherin expression but not that associated with low alkaline phosphatase expression in Manduca sexta.
abstract: To exert their toxic effect, Bacillus thuringiensis Cry1Ab toxin undergoes a sequential binding mechanism with different larval gut proteins including glycosyl-phosphatidyl-inositol anchored proteins like aminopeptidase-N (APN) or alkaline-phosphatase (ALP) and a transmembrane cadherin to form pre-pore structures that insert into the membrane. Cadherin binding induces oligomerization of the toxin by facilitating removal of the N-terminal region, while APN/ALP binding helps in oligomer membrane insertion. Cry1AbMod toxin was engineered to lack N-terminal region of the toxin and shown to counter resistance linked to cadherin mutations. In this manuscript we determined the toxicity of Cry1AbMod to Manduca sexta larvae silenced in the expression of cadherin, ALP or APN receptors. As previously reported Cry1Ab toxicity relied principally in ALP and cadherin in comparison to APN. Our data shows that Cry1AbMod counters resistance associated with low cadherin expression but was not effective against ALP silenced larvae. These results show that Cry1AbMod could be effective against resistance insects linked to mutations on binding molecules involved in toxin oligomerization but not against resistant insects linked to mutations on binding molecules involved in oligomer membrane insertion.
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Isabel
authors.initials: I
authors.lastname: Gómez
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Biviana
authors.initials: B
authors.lastname: Flores
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Bravo
authors.affiliation: Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico. Electronic address: mario@ibt.unam.mx.
authors.forename: Mario
authors.initials: M
authors.lastname: Soberón
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000626:Aminopeptidases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001413:Bacillus thuringiensis / Q000502:physiology*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000276:immunology*; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D004731:Endotoxins / Q000276:immunology*; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D006460:Hemolysin Proteins / Q000276:immunology*; D054884:Host-Pathogen Interactions; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D018402:Manduca / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D015820:Cadherins; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D000469:Alkaline Phosphatase; D000626:Aminopeptidases
keywords: Bacillus thuringiensis; Cry toxins; Oligomerization; RNAi; Toxin–receptor interaction; dsRNA