title: Screening for Bacillus thuringiensis crystal proteins active against the cabbage looper, Trichoplusia ni.
abstract: Toxicity tests were performed to find among Cry1 and Cry2 Bacillus thuringiensis crystal proteins those with high activity against the cabbage looper. Tests were performed with neonate larvae on surface-contaminated artificial diet. The crystal proteins found to be toxic were, from higher to lower toxicity: Cry1Ac, Cry1Ab, Cry1C, Cry2Aa, Cry1J, and Cry1F (LC50 of 1.14.1, 3.4-4.4, 12, 34, 87, and 250 ng/cm2, respectively). Cry1B, Cry1D, and Cry1E can be considered nontoxic (LC50 higher than 2500 ng/cm2). Cry1Aa was moderately toxic to nontoxic, depending on the source (LC50 of 420 ng/cm2 from PGS and 8100 ng/cm2 from Ecogen). In vitro binding assays with trypsin-activated 125I-labeled Cry1Aa, Cry1Ab, and Cry1Ac crystal proteins and brush border membrane vesicles from midgut larvae showed a direct correlation between toxicity and binding affinity. Heterologous competition experiments indicated that Cry1Aa and Cry1F bind, though only at very high concentrations, to the Cry1Ab/Cry1Ac shared high-affinity binding site.
authors.affiliation: Departamento de Microbiología e Immunología, Facultad de Ciencias Biológicas/UANL, Monterrey, NL, México.
authors.forename: M M
authors.initials: MM
authors.lastname: Iracheta
authors.forename: B
authors.initials: B
authors.lastname: Pereyra-Alférez
authors.forename: L
authors.initials: L
authors.lastname: Galán-Wong
authors.forename: J
authors.initials: J
authors.lastname: Ferré
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D007457:Iodine Radioisotopes; D009036:Moths; D010572:Pest Control, Biological
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D007457:Iodine Radioisotopes; C030956:insecticidal crystal protein, Bacillus Thuringiensis