Characterization of a B-type esterase involved in insecticide resistance from the mosquito <i>Culex quinquefasciatus</i>

Karunaratne, S.H.P.P.; Jayawardena, K. G. I.; Hemingway, Janet; Ketterman, Albert J.

doi:10.1042/bj2940575

Cited by 79 publications

(76 citation statements)

References 23 publications

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“…Amplification of a single esterase, coded for by the estβ1" gene, was first shown in the Californian TEM-R strain of mosquito [18]. Immunological and molecular studies have since suggested that the estβ1", estβ1# and estβ2" genes were originally alleles of the same locus [10,20,21]. More recently, cloning of the estα2" cDNA has enabled comparison of the coding regions of the estα and estβ esterase genes [9].…”

Section: Introductionmentioning

confidence: 99%

Co-amplification explains linkage disequilibrium of two mosquito esterase genes in insecticide-resistant Culex quinquefasciatus

Vaughan

Hawkes

Hemingway

1997

Biochemical Journal

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The mosquito Culexquinquefasciatus (Say) is a vector of human disease and a world-wide biting nuisance. Organophosphorus insecticides (OPs) have been widely used to control C. quinquefasciatus populations and this has led to the emergence of OP-resistance. Predominantly, resistance is caused by increased production of two non-specific carboxylesterases, Estα21 and Estβ21. Increased abundance of these esterases is associated with the amplification of their respective genes. The estα21 and estβ21 genes were cloned and sequenced from OP-resistant Sri Lankan C. quinquefasciatus; the two adjacent genes are in a head to head configuration, within a single amplification unit (amplicon). The homology between the two genes suggests that they arose from an ancient duplication event. The two genes have different numbers of exons (estα21 has seven and estβ21 has four); however, the intron/exon boundaries in estβ21 are all conserved in estα21. The two genes are co-amplified in three other mosquito strains with the elevated Estα21/Estβ21 phenotype. Their complete linkage disequilibrium is explained by the location of the two genes involved in resistance within a single amplicon. In insecticide-susceptible C. quinquefasciatus, the non-amplified estα and estβ gene loci are also found in a similar head to head configuration, but the size of the intergenic non-coding region is approx. 1 kb less than in the amplicon. The smaller intergenic spacer is also found in a strain with amplified estβ11, which suggests that extensive laboratory selection for this amplified esterase has not eliminated the non-amplified genes. The intergenic spacer regions have been subcloned and sequenced. They contain numerous possible TATA boxes, promoters and a number of possible regulatory elements with high homology to the consensus sequence of the Barbie box. These latter putative regulatory elements are more numerous in the larger intergenic spacer, which differs from the non-amplified spacer by two large (> 420 bp) and one small (5 bp) insertions.

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Section: Introductionmentioning

confidence: 99%

Co-amplification explains linkage disequilibrium of two mosquito esterase genes in insecticide-resistant Culex quinquefasciatus

Vaughan

Hawkes

Hemingway

1997

Biochemical Journal

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“…1 (11,12). The electrophoretic mobility on native PAGE of the Pel SS-purified Est␣ was reproducibly faster than that of the resistant Est␣2 1 (Fig.…”

Section: Resultsmentioning

confidence: 96%

“…The Pel SS Est␤1 3 K m for pNPA was significantly higher than those of the resistant Est␤2 previously observed for Pel RR (140.8 Ϯ 5.24 M), Dar91 (85.41 Ϯ 3.94 M), and Tanga85 (90.11 Ϯ 6.49 M) (12,17). In contrast, the Pel SS Est␣3 and Est␤1 3 esterase pNPH K m values are not significantly different from those previously reported for Est␣2 1 and Est␤2 1 (17).…”

Section: Discussionmentioning

confidence: 93%

“…Carboxylesterases Est␣ and Est␤ were purified several times from numerous batches of larvae of each strain by sequential column chromatography and preparative electrophoresis as described previously (12,17). Final enzyme preparations were homogeneous as determined by SDS-PAGE.…”

Section: The Nucleotide Sequence(s) Reported In This Paper Has Been Smentioning

confidence: 99%

“…The role of the amplified esterases in resistance is sequestration, which is rapid binding and slow turnover of insecticides (11)(12)(13). 2 The current study elucidates the relative efficiencies of the purified esterases from a susceptible and two further resistant strains at binding the carbamates and biologically active oxon analogues of the organophosphorus insecticides.…”

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confidence: 99%

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Kinetic and Molecular Differences in the Amplified and Non-amplified Esterases from Insecticide-resistant and Susceptible Culex quinquefasciatus Mosquitoes

Karunaratne¹,

Hemingway

Jayawardena³

et al. 1995

Journal of Biological Chemistry

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Two non-amplified esterases were purified from the insecticide-susceptible Pel SS strain of Culex quinquefasciatus. These were the two major esterase activity peaks in this strain. The two corresponding amplified carboxylesterases, Est␣2 and Est␤2, involved in organophosphate sequestration were purified from two resistant C. quinquefasciatus strains. The Pel SS esterases were significantly less reactive with the organophosphates than those from the resistant strains. One of the Pel SS esterases was electrophoretically identical to amplified Culex Est␤1. However, it differed kinetically, and in its nucleotide and predicted amino acid sequences from the two characterized amplified Est␤1s, it is classified as Est␤1 3 . Restriction fragment analysis suggested Pel SS has only one Est␣ and one Est␤ gene, while the resistant Pel RR has both amplified and non-amplified forms of Est␣ and Est␤. The EcoRI fragments for both Pel SS esterases were distinct from those of the amplified Est␣2 1 , Est␤2 1 , or Est␤1 1&2 . An esterase with the same size EcoRI fragment as Est␤1 3 was also present in Pel RR. This and restriction enzyme fragment analysis of C. quinquefasciatus field populations suggest that variability of the susceptible alleles may be lower than previously suggested. A non-amplified Est␣ with a unique EcoRI band was present in Pel RR. The previous esterase purification procedures may not have separated these amplified and non-amplified alleles. Hence, the small differences between the purified esterases from resistant strains may reflect mixtures of identical amplified alleles with different non-amplified alleles, which have significantly different k a values.The use of pesticides, both directly and indirectly against the mosquito Culex quinquefasciatus, has resulted in the selection of broad spectrum organophosphate and carbamate resistance. The most commonly selected resistance mechanism is the increased activity of Est␣2 and Est␤2 carboxylesterases (EC 3.1.1.1) (A 2 and B 2 esterases on an earlier classification) (1-6).Classification of these esterases is based on their preferences for ␣-or ␤-naphthyl acetate, their mobility on native polyacrylamide gel electrophoresis (PAGE), 1 and their nucleotide sequence (1). The overproduction of the Est␣2 1 and a series of Est␤ esterases is due to gene amplification (1,5,7,8). Identical EcoRI restriction fragment sizes of the amplified Est␤2 from resistant C. quinquefasciatus worldwide has been reported, in contrast to a high level of variability in Est␤ from insecticidesusceptible mosquitoes (9). A cDNA with 97% identity to Est␤2 1 has been cloned from an insecticide susceptible strain (Pel SS) of C. quinquefasciatus from Sri Lanka (8); however, the protein has not been characterized. After native starch or PAGE of homogenates of individual resistant Culex larvae of the amplified Est␣2/Est␤2 esterase phenotype, two electromorphs can be visualized. Under the same conditions, no esterase bands are visible in homogenates of susceptible insects. This has lead to the suggestio...

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Multiple Resistance in the Larger House FlyMusca domesticain Germany

et al. 1996

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Populations of the housefly Musca domestica isolated from farms in different German districts with strong resistance problems were compared to laboratory strains with varying resistance spectra. Resistance against pyrethroids, organophosphates and carbamates was tested using impregnated filter papers, and by topical application using a susceptible housefly strain (origin WHO) for comparison. The multi-resistant fly strains tested had a strong resistance against these insecticide groups, ranging from 37-to > 10000-fold for organophosphates and 150-to > 6600-fold for pyrethroids. The constituent enantiomer pairs of the a-cyano-pyrethroid cyfluthrin were tested, as was beta-cyfluthrin. With respect to multi-resistant fly strains, the isomers I1 and IV had the best activity, with LD,, values of 0.012 and 0.014 pg per fly, respectively. In addition, different groups of insect growth regulators (juvenile hormone analogues, chitin synthesis inhibitors and one triazine derivative) were tested in a special larvicidal test. The chitin synthesis inhibitors were quite effective against multi-resistant M. domestica strains except for one strain with strong resistance against chitin synthesis inhibitors, developed after extensive treatments with benzoylphenylureas for several years. The fly strains tested were not resistant against cyromazine. Additionally, the insecticides were combined with the synergists piperonyl butoxide, tributylphosphorotrithioate (DEF) and Cibacron blue and tested against the fly strain with the strongest resistance spectrum ('Grimm') in comparison to the susceptible strain ('WHO-"). Piperonyl butoxide had the greatest effect on the efficacy of cyfluthrin followed by Cibacron blue and DEF. In a parallel investigation with susceptible and resistant house fly strains, different enzyme activities related with resistance mechanisms were tested, e.g. glutathione S-transferase (3.5-fold) and mixed-function oxidase (2.3-fold). Implications of these results for management of insecticide resistance in M. domestica are discussed.

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Characterization of a B-type esterase involved in insecticide resistance from the mosquito Culex quinquefasciatus

Cited by 79 publications

References 23 publications

Co-amplification explains linkage disequilibrium of two mosquito esterase genes in insecticide-resistant Culex quinquefasciatus

Co-amplification explains linkage disequilibrium of two mosquito esterase genes in insecticide-resistant Culex quinquefasciatus

Kinetic and Molecular Differences in the Amplified and Non-amplified Esterases from Insecticide-resistant and Susceptible Culex quinquefasciatus Mosquitoes

Multiple Resistance in the Larger House FlyMusca domesticain Germany

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