title: Presence and significance of Bacillus thuringiensis Cry proteins associated with the Andean weevil Premnotrypes vorax (Coleoptera: Curculionidae).
abstract: The Andean weevil Premnotrypes vorax represents an important cause of damage to Colombian potato crops. Due to the impact of this plague on the economy of the country, we searched for new alternatives for its biological control, based on the entomopathogenic bacteria Bacillus thuringiensis. A total of 300 B. thuringiensis strains obtained from potato plantations infested with P. vorax were analyzed through crystal morphology, SDS-PAGE, PCR and bioassays. We used site-directed mutagenesis to modify the Cry3Aa protein. Most of the B. thuringiensis isolates had a bipyramidal crystal morphology. SDS-PAGE analyses had seven strains groups with delta-endotoxins from 35 to 135 kDa. The genes cry 2 and cry 1 were significantly more frequent in the P. vorax habitat (PCR analyses). Three mutant toxins, 1 (D354E), 2 (R345A, DeltaY350, DeltaY351), and 3 (Q482A, S484A, R485A), were analyzed to assess their activity against P. vorax larvae. Toxicity was low, or absent, against P. vorax for isolates, wild type cry 3Aa and cry 3Aa mutants. The genetic characterization of the collection provides opportunities for the selection of strains to be tested in bioassays against other insect pests of agricultural importance, and for designing Cry proteins with improved insecticidal toxicity.
authors.affiliation: Instituto de Biotecnología, Universidad Nacional de Colombia, Santafé de Bogotá DC, Colombia. salopezp@unal.edu.co
authors.forename: Silvio Alejandro
authors.initials: SA
authors.lastname: López-Pazos
authors.forename: John Wilson
authors.initials: JW
authors.lastname: Martínez
authors.forename: Adriana Ximena
authors.initials: AX
authors.lastname: Castillo
authors.forename: Jairo Alonso
authors.initials: JA
authors.lastname: Cerón Salamanca
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000633:toxicity*; D001681:Biological Assay; D004591:Electrophoresis, Polyacrylamide Gel; D004731:Endotoxins / Q000302:isolation & purification / Q000633:toxicity*; D006460:Hemolysin Proteins / Q000302:isolation & purification / Q000633:toxicity*; D016297:Mutagenesis, Site-Directed; D010572:Pest Control, Biological; D016133:Polymerase Chain Reaction; D011198:Solanum tuberosum / Q000469:parasitology*; D048889:Weevils / Q000187:drug effects* / Q000382:microbiology
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis