Amplification of various esterase B's responsible for organophosphate resistance inCulex mosquitoes

Raymond, M.; Beyssat-Arnaouty, V.; Sivasubramanian, Natarajan; Mouchès, C.; Georghiou, George P.; Pasteur, Nicole

doi:10.1007/bf02399670

Cited by 84 publications

(78 citation statements)

References 9 publications

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“…The approx. 80-fold copy difference between PelSS and PelRR estα and estβ genes represents a level of gene amplification between those reported previously [6,7,10,11,20]. It is clear from population studies that amplification levels vary between individuals over time ( [20], and M. G. Paton, S. H. P. P. Karunaratne and J. Hemingway, unpublished work), through variation in organophosphate selection pressure, promoting the loss or gain of gene copies, possibly through unequal sister-chromatid exchange as suggested for mosquitoes and aphids [20,32].…”

Section: Discussionsupporting

confidence: 47%

“…The molecular mechanism underlying the overproduction of esterases in Culex is gene amplification [6][7][8][9][10][11][12] and regulation of gene expression [10,11,13]. The most prevalent amplified esterase genes are estα2" and estβ2", which occur worldwide [1,14,15].…”

Section: Introductionmentioning

confidence: 99%

“…Original estimates of estβ1 gene copy number in the TEMR strain of C. quinquefasciatus were reported as 250 copies per cell in resistant mosquitoes [6] and later revised to 150 copies [7].…”

Section: Introductionmentioning

confidence: 99%

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Quantitative analysis of gene amplification in insecticide-resistant Culex mosquitoes

Paton

Karunaratne

Giakoumaki

et al. 2000

Biochemical Journal

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The amplification of carboxylesterase structural genes followed by their overexpression is the most common mechanism of resistance to organophosphorus insecticides in Culex mosquitoes. Most resistant Culex quinquefasciatus mosquitoes have coamplified estα2" and estβ2" genes. Recently, Southern, DNA dotblot analysis and phosphorimaging technology were used to quantify the est gene copy number in aphids and mosquitoes. Although more accurate than autoradiography, this method relies on probe hybridization, which can be variable. We have directly measured gene and mRNA copy number by using realtime quantitative PCRs in mosquitoes. The acquisition of fluorescence from incorporation of the double-strand-specific dye SYBR GreenI into a PCR product once per cycle is used to provide an absolute quantification of the initial template copy number. Thus it has been possible to show that estα2" and estβ2"

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Section: Discussionsupporting

confidence: 47%

Section: Introductionmentioning

confidence: 99%

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Quantitative analysis of gene amplification in insecticide-resistant Culex mosquitoes

Paton

Karunaratne

Giakoumaki

et al. 2000

Biochemical Journal

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“…This strongly suggests that the two genes arose through an ancestral gene-duplication event. This event is likely to have occurred before Culex speciation since elevated Estα and\or Estβ esterases have been identified in at least two further Culex species, C. tarsalis and C. tritaeniorhynchus [19,25,26]. The outcome of this initial duplication event could have resulted in the genes being located next to each other.…”

Section: Discussionmentioning

confidence: 99%

“…Increased expression of Estα and Estβ esterases involved in OP-resistance is associated with gene amplification [9,10,18,19]. Amplification of a single esterase, coded for by the estβ1" gene, was first shown in the Californian TEM-R strain of mosquito [18].…”

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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A molecular test to identify resistance alleles at the amplified esterase locus in the mosquitoCulex pipiens

et al. 2000

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A new PCR/RFLP method is presented to identify all described alleles involved in resistance at the Ester locus in the mosquito Culex pipiens. The ef®ciency of this method as well as its advantages compared with the traditional identi®cation technique (starch gel electrophoresis) have been tested in four natural samples from France, Tunisia and California. This simple and fast molecular test is a very convenient tool for studies in ®eld populations and laboratory strains.

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Amplification of various esterase B's responsible for organophosphate resistance inCulex mosquitoes

Cited by 84 publications

References 9 publications

Quantitative analysis of gene amplification in insecticide-resistant Culex mosquitoes

Quantitative analysis of gene amplification in insecticide-resistant Culex mosquitoes

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

A molecular test to identify resistance alleles at the amplified esterase locus in the mosquitoCulex pipiens

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