title: Stability of Culex quinquefasciatus resistance to Bacillus sphaericus evaluated by molecular tools.
abstract: Bacillus sphaericus binary toxin action on Culex quinquefasciatus larvae relies on the binding to Cqm1alpha-glucosidases, which act as midgut receptors. Resistance of two laboratory-selected colonies is associated with the allele cqm1(REC) that prevents Cqm1 expression as membrane-bound molecules. This study evaluated stability of resistance after the interruption of selection pressure and introduction of susceptible individuals in these colonies. Bioassays showed that frequency of resistant larvae did not decrease throughout 11 generations, under these conditions, and it was associated to a similar frequency of larvae lacking the Cqm1alpha-glucosidase receptor, detected by in gel enzymatic assays. Direct screening of the cqm1(REC) allele, by specific PCR, showed that its frequency remained stable throughout 11 generations. Parental resistant colony did not display biological costs regarding fecundity, fertility and pupal weight and data from susceptibility assays, enzymatic assays and PCR screening showed that cqm1(REC) was not disfavored in competition with the susceptible allele and persisted in the progenies, in the lack of selection pressure. Characterization of molecular basis of resistance is essential for developing diagnostic tools and data have relevant implication for the establishment of strategies for resistance management.
authors.affiliation: Departament of Entomology, Centro de Pesquisas Aggeu Magalhães/FIOCRUZ, Av. Moraes Rego s/n, Cidade Universitária, Recife-PE 50670-420, Brazil.
authors.forename: Liliane Barbosa
authors.initials: LB
authors.lastname: Amorim
authors.forename: Rosineide Arruda
authors.initials: RA
authors.lastname: de Barros
authors.forename: Karlos Diogo de Melo
authors.initials: KD
authors.lastname: Chalegre
authors.forename: Cláudia Maria Fontes
authors.initials: CM
authors.lastname: de Oliveira
authors.forename: Lêda Narcisa
authors.initials: LN
authors.lastname: Regis
authors.forename: Maria Helena Neves Lobo
authors.initials: MH
authors.lastname: Silva-Filha
mesh_terms: D000483:Alleles; D000818:Animals; D001407:Bacillus / Q000502:physiology*; D003465:Culex / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D005260:Female; D054884:Host-Pathogen Interactions; D007113:Immunity, Innate; D019476:Insect Proteins / Q000235:genetics; D008297:Male; D016133:Polymerase Chain Reaction; D000520:alpha-Glucosidases / Q000235:genetics
chemical_list: D019476:Insect Proteins; D000520:alpha-Glucosidases