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CO-SELECTION AND REPLACEMENT OF RESISTANCE ALLELES TO LYSINIBACILLUS SPHAERICUS IN A CULEX QUINQUEFASCIATUS COLONY
allele replacement
alpha-Glucosidases
Animals
Bacillaceae
Bacterial Toxins
cqm1 alleles
Crosses, Genetic
Culex
Evolution, Molecular
Gene Frequency
Genes, Insect
Gram-Positive Bacterial Infections
Insect Proteins
Male
Mutation
receptors
Selection, Genetic
alpha-glucosidases
Autor
Afiliación
Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Recife, PE, Brasil
Resumen en ingles
The Cqm1 α-glucosidase, expressed within the midgut of Culex quinquefasciatus mosquito larvae, is the receptor for the Binary toxin (Bin) from the entomopathogen Lysinibacillus sphaericus. Mutations of the Cqm1 α-glucosidase gene cause high resistance levels to this bacterium in both field and laboratory populations, and a previously described allele, cqm1REC, was found to be associated with a laboratory-resistant colony (R2362). This study described the identification of a novel resistance allele, cqm1REC-2, that was co-selected with cqm1REC within the R2362 colony. The two alleles display distinct mutations but both generate premature stop codons that prevent the expression of midgut-bound Cqm1 proteins. Using a PCR-based assay to monitor the frequency of each allele during long-term maintenance of the resistant colony, cqm1REC was found to predominate early on but later was replaced by cqm1REC-2 as the most abundant resistance allele. Homozygous larvae for each allele were then generated that displayed similar high-resistance phenotypes with equivalent low levels of transcript and lack of protein expression for both cqm1REC and cqm1REC-2. In progeny from a cross of homozygous individuals for each allele at a 1 : 1 ratio, analyzed for ten subsequent generations, cqm1REC showed a higher frequency than cqm1REC-2. The replacement of cqm1REC by cqm1REC -2 observed in the R2362 colony, kept for 210 generations, indicates changes in fitness related to traits that are unknown but linked to these two alleles, and constitutes a unique example of evolution of resistance within a controlled laboratory environment.
Palabras clave en ingles
Bacillaceaeallele replacement
alpha-Glucosidases
Animals
Bacillaceae
Bacterial Toxins
cqm1 alleles
Crosses, Genetic
Culex
Evolution, Molecular
Gene Frequency
Genes, Insect
Gram-Positive Bacterial Infections
Insect Proteins
Male
Mutation
receptors
Selection, Genetic
alpha-glucosidases
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