title: Increase in larval gut proteolytic activities and Bti resistance in the Dengue fever mosquito.
abstract: The bioinsecticide Bacillus thuringiensis var. israelensis (Bti) is increasingly used worldwide for mosquito control. Although no established resistance to Bti has been described in the field so far, a resistant Aedes aegypti strain (LiTOX strain) was selected in the laboratory using field-collected leaf litter containing Bti toxins. This selected strain exhibits a moderate resistance level to Bti, but a high resistance level to individual Cry toxins. As Bti contains four different toxins, generalist resistance mechanisms affecting mosquito tolerance to different toxins were expected in the resistant strain. In the present work, we show that the resistant strain exhibits an increase of various gut proteolytic activities including trypsins, leucine-aminopeptidases, and carboxypeptidase A activities. These elevated proteolytic activities resulted in a faster activation of Cry4Aa protoxins while Cry4Ba or Cry11Aa were not affected. These results suggest that changes in proteolytic activities may contribute to Bti resistance in mosquitoes together with other mechanisms.
authors.affiliation: Laboratoire d'Ecologie Alpine, LECA-UMR 5553, Université de Grenoble 1, Grenoble Cedex, France. guillaume.tetreau@gmail.com
authors.forename: Guillaume
authors.initials: G
authors.lastname: Tetreau
authors.forename: Renaud
authors.initials: R
authors.lastname: Stalinski
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: David
authors.forename: Laurence
authors.initials: L
authors.lastname: Després
mesh_terms: D000330:Aedes / Q000201:enzymology* / Q000254:growth & development / Q000382:microbiology*; D000818:Animals; D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D041981:Gastrointestinal Tract / Q000201:enzymology; D006460:Hemolysin Proteins; D019476:Insect Proteins / Q000378:metabolism; D007814:Larva / Q000201:enzymology / Q000254:growth & development / Q000382:microbiology; D045727:Metalloexopeptidases / Q000378:metabolism; D010572:Pest Control, Biological; D059748:Proteolysis; D012697:Serine Endopeptidases / Q000378:metabolism
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D045727:Metalloexopeptidases; D012697:Serine Endopeptidases