title: Defence mechanisms against insecticides temephos and diflubenzuron in the mosquito Aedes caspius: the P-glycoprotein efflux pumps.
abstract: P-glycoproteins (P-gps) are efflux transporters found in cells of a broad range of both procaryotic and eukaryotic taxa, whose action is to relieve the cells of multiple, structurally dissimilar, toxic compounds. The possible role of P-gps in defence against the insecticides temephos and diflubenzuron was investigated in the mosquito Aedes caspius (Pallas), also known as Ochlerotatus (Aedes) caspius (Diptera: Culicidae), and the genomic DNA sequences encoding for P-gp transporters were isolated to provide molecular instruments for future research into the expression and characterization of genes codifying for P-gps in this mosquito species. Mosquito larvae were treated with insecticides alone and in conjunction with a sublethal dose of the P-gp inhibitor verapamil. The inhibition of P-gps reduced the LD(50) values of temephos and diflubenzuron by factors of 3.5 and 16.4, respectively, suggesting the potential involvement of P-gps in insecticide defence. Using a polymerase chain reaction (PCR)-based approach, a 481-bp sequence was isolated. The inferred nucleotide sequence shows high homology with the C-terminal sequence of known P-gps. The isolation and characterization of a putative P-gp sequence from Ae. caspius is the first step towards a better molecular understanding of the role played by multidrug transporters in the defence against insecticides in this species. This knowledge may open the way to a novel control strategy based on the inhibition of pest defences. The beneficial consequences of the inhibition of efflux pumps in improving insecticide performance are discussed.
authors.affiliation: Department of Genetics and Molecular Biology, University La Sapienza of Rome, Rome, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Porretta
authors.forename: M
authors.initials: M
authors.lastname: Gargani
authors.forename: R
authors.initials: R
authors.lastname: Bellini
authors.forename: A
authors.initials: A
authors.lastname: Medici
authors.forename: F
authors.initials: F
authors.lastname: Punelli
authors.forename: S
authors.initials: S
authors.lastname: Urbanelli
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D000330:Aedes / Q000187:drug effects* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001681:Biological Assay / Q000662:veterinary; D004132:Diflubenzuron / Q000494:pharmacology; D007300:Insect Control / Q000379:methods*; D007303:Insect Vectors / Q000187:drug effects / Q000378:metabolism; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva; D007928:Lethal Dose 50; D008970:Molecular Weight; D012689:Sequence Homology, Nucleic Acid; D000002:Temefos / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D007306:Insecticides; D014700:Verapamil; D004132:Diflubenzuron; D000002:Temefos