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- Title
A second independent resistance mechanism to Bacillus sphaericus binary toxin targets its α-glucosidase receptor in Culex quinquefasciatus.
- Authors
Romão, Tatiany Patrícia; de Melo Chalegre, Karlos Diogo; Key, Shana; Junqueira Ayres, Constância Flávia; Fontes de Oliveira, Cláudia Maria; de-Melo-Neto, Osvaldo Pompílio; Lobo Silva-Filha, Maria Helena Neves
- Abstract
The entomopathogen Bacillus sphaericus is an important tool for the vector control of Culex sp., and its effectiveness has been validated in field trials. The appearance of resistance to this bacterium, however, remains a threat to its use, and attempts have been made to understand the resistance mechanisms. Previous work showed that the resistance to B. sphaericus in a Culex quinquefasciatus colony is associated with the absence of the ≈ 60-kDa binary toxin receptor in larvae midgut microvilli. Here, the gene encoding the C. quinquefasciatus toxin receptor, Cqm1, was cloned and sequenced from a susceptible colony. The deduced amino-acid sequence confirmed its identity as an α-glucosidase, and analysis of the corresponding gene sequence from resistant larvae implicated a 19-nucleotide deletion as the basis for resistance. This deletion changes the ORF and originates a premature stop codon, which prevents the synthesis of the full-length Cqm1. Expression of the truncated protein, however, was not detected when whole larvae extracts were probed with antibodies raised against an N-terminal 45-kDa recombinant fragment of Cqm1. It seems that the premature stop codon directs the mutated cqm1 to the nonsense-mediated decay pathway of mRNA degradation. In-gel assays confirmed that a single α-glucosidase protein is missing from the resistant colony. Further in vitro affinity assays showed that the recombinant fragment binds to the toxin, and mapped the binding site to the N-terminus of the receptor.
- Subjects
ENTOMOPATHOGENIC fungi; PATHOGENIC fungi; BACILLUS sphaericus; MICROBIAL toxins; CULEX quinquefasciatus; NUCLEOTIDE sequence
- Publication
FEBS Journal, 2006, Vol 273, Issue 12, p1556
- ISSN
1742-464X
- Publication type
Article
- DOI
10.1111/j.1742-4658.2006.05177.x