title: A new allele conferring resistance to Lysinibacillus sphaericus is detected in low frequency in Culex quinquefasciatus field populations.
abstract: BACKGROUND
  The Cqm1 α-glucosidase of Culex quinquefasciatus larvae acts as the midgut receptor for the binary toxin of the biolarvicide Lysinibacillus sphaericus. Mutations within the cqm1 gene can code for aberrant polypeptides that can no longer be properly expressed or bind to the toxin, leading to insect resistance. The cqm1 REC and cqm1 REC-2 alleles were identified in a laboratory selected colony and both displayed mutations that lead to equivalent phenotypes of refractoriness to L. sphaericus. cqm1 REC was first identified as the major resistance allele in this colony but it was subsequently replaced by cqm1 REC-2 , suggesting the better adaptive features of the second allele. The major aim of this study was to evaluate the occurrence of cqm1 REC-2 and track its origin in field populations where cqm1 REC was previously identified.
  
  
  METHODS
  The screening of the cqm1 REC-2 allele was based on more than 2000 C. quinquefasciatus larvae from five localities in the city of Recife, Brazil and used a multiplex PCR assay that is also able to identify cqm1 REC . Full-length sequencing of the cqm1 REC-2 and selected cqm1 samples was performed to identify further polymorphisms between these alleles.
  
  
  RESULTS
  The cqm1 REC-2 allele was found in field samples, specifically in two heterozygous individuals from a single locality with an overall frequency and distribution much lower than that observed for cqm1 REC . The full-length sequences from these two cqm1 REC-2 copies were almost identical to the cqm1 REC-2 derived from the resistant colony but displayed more than 30 SNPs when compared with cqm1 and cqm1 REC . The cqm1 REC and cqm1 REC-2 resistant alleles were found to be associated with two distinct sets of wild-type cqm1 variants found in field populations.
  
  
  CONCLUSIONS
  The cqm1 REC-2 allele occurs in populations in Recife and was probably already present in the samples used to establish the laboratory resistant colony. The data generated indicates that cqm1 REC-2 can be selected in field populations, although its low frequency and distribution in Recife suggest that cqm1 REC-2 presents a lower risk of selection compared to cqm1 REC .
authors: Department of Entomology, Centro de Pesquisas Aggeu Magalhães-FIOCRUZ, Recife, PE, 50740-465, Brazil. hsuzany@hotmail.com.
authors: Heverly Suzany Gouveia
authors: HS
authors: Menezes
authors: Department of Entomology, Centro de Pesquisas Aggeu Magalhães-FIOCRUZ, Recife, PE, 50740-465, Brazil. diogochalegre@gmail.com.
authors: Karlos Diogo de Melo
authors: KD
authors: Chalegre
authors: Department of Entomology, Centro de Pesquisas Aggeu Magalhães-FIOCRUZ, Recife, PE, 50740-465, Brazil. taty@cpqam.fiocruz.br.
authors: Tatiany Patrícia
authors: TP
authors: Romão
authors: Department of Entomology, Centro de Pesquisas Aggeu Magalhães-FIOCRUZ, Recife, PE, 50740-465, Brazil. claudia@cpqam.fiocruz.br.
authors: Cláudia Maria Fontes
authors: CM
authors: Oliveira
authors: Department of Microbiology, Centro de Pesquisas Aggeu Magalhães-FIOCRUZ, Recife, PE, 50740-465, Brazil. opmn@cpqam.fiocruz.br.
authors: Osvaldo Pompílio
authors: OP
authors: de-Melo-Neto
authors: Department of Entomology, Centro de Pesquisas Aggeu Magalhães-FIOCRUZ, Recife, PE, 50740-465, Brazil. mhneves@cpqam.fiocruz.br.
authors: Maria Helena Neves Lobo
authors: MH
authors: Silva-Filha
mesh_terms: D000483:Alleles; D000818:Animals; D001406:Bacillaceae / Q000276:immunology*; D001427:Bacterial Toxins / Q000633:toxicity*; D001938:Brazil; D002947:Cities; D003465:Culex / Q000235:genetics / Q000276:immunology / Q000382:microbiology*; D017344:Genes, Insect; D007305:Insecticide Resistance; D007306:Insecticides / Q000633:toxicity*; D060885:Multiplex Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
chemical_list: D001427:Bacterial Toxins; D007306:Insecticides