Pasteur N

References (48)

Title : Dynamic of resistance alleles of two major insecticide targets in Anopheles gambiae (s.l.) populations from Benin, West Africa - Assogba_2020_Parasit.Vectors_13_134
Author(s) : Assogba BS , Pasteur N , Makoundou P , Unal S , Baba-Moussa L , Labbe P , Weill M
Ref : Parasit Vectors , 13 :134 , 2020
Abstract : BACKGROUND: Insecticide resistance is a growing concern for malaria control and vector control effectiveness relies on assessing it distribution and understanding its evolution. METHODS: We assessed resistance levels and the frequencies of two major target-site mutations, L1014F-VGSC and G119S-ace-1, conferring resistance to pyrethroids (PYRs) and carbamates/organophosphates (CXs/OPs) insecticides. These data were compared to those acquired between 2006 and 2010 to follow resistance evolutionary trends over ten years. RESULTS: We report the results of a 3-year survey (2013-2015) of insecticide resistance in 13 localities across the whole country of Benin. Permethrin (PYR) resistance was found in all populations tested, L1014F-VGSC being almost fixed everywhere, while bendiocarb resistance was limited to a few localities, G119S-ace-1 remaining rare, with very limited variations during surveyed period. Interestingly, we found no effect of the type of insecticide pressure on the dynamics of these mutations. CONCLUSIONS: These results confirm both the high prevalence of PYR resistance and the potential of CXs/OPs as short- to medium-term alternatives in Benin. They also underline the need for regular resistance monitoring and informed management in their usage, as the G119S-ace-1 mutation is already present in Benin and surrounding countries. Their unwise usage would rapidly lead to its spread, which would jeopardize PYR-resistant Anopheles control.
ESTHER : Assogba_2020_Parasit.Vectors_13_134
PubMedSearch : Assogba_2020_Parasit.Vectors_13_134
PubMedID: 32171326

Title : High chlorpyrifos resistance in Culex pipiens mosquitoes: strong synergy between resistance genes - Alout_2016_Heredity.(Edinb)_116_224
Author(s) : Alout H , Labbe P , Berthomieu A , Makoundou P , Fort P , Pasteur N , Weill M
Ref : Heredity (Edinb) , 116 :224 , 2016
Abstract : We investigated the genetic determinism of high chlorpyrifos resistance (HCR), a phenotype first described in 1999 in Culex pipiens mosquitoes surviving chlorpyrifos doses 1 mg l(-1) and more recently found in field samples from Tunisia, Israel or Indian Ocean islands. Through chlorpyrifos selection, we selected several HCR strains that displayed over 10 000-fold resistance. All strains were homozygous for resistant alleles at two main loci: the ace-1 gene, with the resistant ace-1(R) allele expressing the insensitive G119S acetylcholinesterase, and a resistant allele of an unknown gene (named T) linked to the sex and ace-2 genes. We constructed a strain carrying only the T-resistant allele and studied its resistance characteristics. By crossing this strain with strains harboring different alleles at the ace-1 locus, we showed that the resistant ace-1(R) and the T alleles act in strong synergy, as they elicited a resistance 100 times higher than expected from a simple multiplicative effect. This effect was specific to chlorpyrifos and parathion and was not affected by synergists. We also examined how HCR was expressed in strains carrying other ace-1-resistant alleles, such as ace-1(V) or the duplicated ace-1(D) allele, currently spreading worldwide. We identified two major parameters that influenced the level of resistance: the number and the nature of the ace-1-resistant alleles and the number of T alleles. Our data fit a model that predicts that the T allele acts by decreasing chlorpyrifos concentration in the compartment targeted in insects.
ESTHER : Alout_2016_Heredity.(Edinb)_116_224
PubMedSearch : Alout_2016_Heredity.(Edinb)_116_224
PubMedID: 26463842

Title : Biochemical Characterization of the Esterases Al and Bl Associated with Organophosphate Resistance in the Culex pipiens L. - Fournier_1987_Pestic.Biochem.Physiol_27_211
Author(s) : Fournier D , Bride JM , Mouches C , Raymond M , Magnin M , Berge JB , Pasteur N , Georghiou GP
Ref : Pestic Biochem Physiol , 27 :211 , 2015
Abstract : Two esterases, A1 and B1, displaying a high activity in organophosphate (OP) resistant Culex pipiens L. from southern France and in C. quinquefasciatus Say from California, respectively, have been analyzed. Both enzymes are shown to be soluble and to constitute a large proportion of the proteins (1-3% for esterase A1 and 6-12% for esterase B1). The size of native esterase A1 was estimated between 118 and 134 kDa, that of esterase B1 67 kDa. Upon SDS denaturation, esterase B1 leads a single polypeptide of 67 kDa which suggests that it is a monomeric protein; esterase A1 leads also a single polypeptide of 60 kDa suggesting a homodimeric structure of the protein. These observations are discussed with regards to esterase E4 of Myzus persicae Sultz.
ESTHER : Fournier_1987_Pestic.Biochem.Physiol_27_211
PubMedSearch : Fournier_1987_Pestic.Biochem.Physiol_27_211

Title : GENE-dosage effects on fitness in recent adaptive duplications: ace-1 in the mosquito Culex pipiens - Labbe_2014_Evolution_68_2092
Author(s) : Labbe P , Milesi P , Yebakima A , Pasteur N , Weill M , Lenormand T
Ref : Evolution , 68 :2092 , 2014
Abstract : Gene duplications have long been advocated to contribute to the evolution of new functions. The role of selection in their early spread is more controversial. Unless duplications are favored for a direct benefit of increased expression, they are likely detrimental. In this article, we investigated the case of duplications favored because they combine already functionally divergent alleles. Their gene-dosage/fitness relations are poorly known because selection may operate on both overall expression and duplicates relative dosage. Using the well-documented case of Culex pipiens resistance to insecticides, we compared strains with various ace-1 allele combinations, including two duplicated alleles carrying both susceptible and resistant copies. The overall protein activity was nearly additive, but, surprisingly, fitness correlated better with the relative proportion of susceptible and resistant copies rather than any absolute measure of activity. Gene dosage is thus crucial, duplications stabilizing a "heterozygote" phenotype. It corroborates the view that these were favored because they fix a permanent heterosis, thereby solving the irreducible trade-off between resistance and synaptic transmission. Moreover, we showed that the contrasted successes of the two duplicated alleles in natural populations depend on genetic changes unrelated to ace-1, confirming the probable implication of recessive sublethal mutations linked to structural rearrangements in some duplications.
ESTHER : Labbe_2014_Evolution_68_2092
PubMedSearch : Labbe_2014_Evolution_68_2092
PubMedID: 24494966

Title : Insecticide resistance in the Anopheles gambiae complex in Benin: a nationwide survey - Djogbenou_2011_Med.Vet.Entomol_25_256
Author(s) : Djogbenou L , Pasteur N , Akogbeto M , Weill M , Chandre F
Ref : Med Vet Entomol , 25 :256 , 2011
Abstract : Benin has embraced World Health Organization-recommended preventive strategies to control malaria. Its National Malaria Control Programme is implementing and/or coordinating various actions and conducting evaluation trials of mosquito control strategies. Mosquito control is based on the use of insecticide-treated nets and indoor residual spraying, but the efficacy of these strategies to control malaria vectors is endangered by insecticide resistance. Here, we present the results of a nationwide survey on the status of insecticide susceptibility and resistance in Anopheles gambiae s.l. (Diptera: Culicidae) carried out in Benin in 2006-2007 (i.e. before extensive vector control was undertaken). Overall, our study showed that the S molecular form of An. gambiae s.s. predominates and is widely distributed across the country, whereas the frequency of the M form shows a strong decline with increasing latitude. Susceptibility to DDT, permethrin, carbosulfan and chlorpyrifos-methyl was assessed; individual mosquitoes were identified for species and molecular forms, and genotyped for the kdr and ace-1 loci. Full susceptibility to chlorpyrifos-methyl was recorded and very few samples displayed resistance to carbosulfan. High resistance levels to permethrin were detected in most samples and almost all samples displayed resistance to DDT. The kdr-Leu-Phe mutation was present in all localities and in both molecular forms of An. gambiae s.s. Furthermore, the ace-1(R) mutation was predominant in the S form, but absent from the M form. By contrast, no target modification was observed in Anopheles arabiensis. Resistance in the An. gambiae S molecular form in this study seemed to be associated with agricultural practices. Our study showed important geographic variations which must be taken into account in the vector control strategies that will be applied in different regions of Benin. It also emphasizes the need to regularly monitor insecticide resistance across the country and to adapt measures to manage resistance.
ESTHER : Djogbenou_2011_Med.Vet.Entomol_25_256
PubMedSearch : Djogbenou_2011_Med.Vet.Entomol_25_256
PubMedID: 21155858

Title : High incidence of ace-1 duplicated haplotypes in resistant Culex pipiens mosquitoes from Algeria - Alout_2011_Insect.Biochem.Mol.Biol_41_29
Author(s) : Alout H , Labbe P , Pasteur N , Weill M
Ref : Insect Biochemistry & Molecular Biology , 41 :29 , 2011
Abstract : The status of genes conferring resistance to organophosphate and carbamate insecticides has been examined in Culex pipiens pipiens mosquitoes sampled in Algeria. Presence of overproduced esterases was sporadic, but acetylcholinesterase-1 resistant alleles were observed in almost all samples. We focused our study on the AChE1 G119S substitution characterized in almost all samples, mostly at the heterozygous state. A genetic test revealed the presence of ace-1 duplication associating a susceptible and a resistant ace-1 copy. Molecular characterization showed a high occurrence of ace-1 duplication with six distinct duplicated alleles out of four samples. The inferred frequency of duplicated allele suggests that it is replacing the single resistant G119S allele. Finally, we discuss the mechanism at the origin of these duplicated haplotypes and their consequences on the management of insecticide resistance.
ESTHER : Alout_2011_Insect.Biochem.Mol.Biol_41_29
PubMedSearch : Alout_2011_Insect.Biochem.Mol.Biol_41_29
PubMedID: 20887788

Title : Insecticide resistance in Culex pipiens quinquefasciatus and Aedes albopictus mosquitoes from La Reunion Island - Tantely_2010_Insect.Biochem.Mol.Biol_40_317
Author(s) : Tantely ML , Tortosa P , Alout H , Berticat C , Berthomieu A , Rutee A , Dehecq JS , Makoundou P , Labbe P , Pasteur N , Weill M
Ref : Insect Biochemistry & Molecular Biology , 40 :317 , 2010
Abstract : Resistance to insecticides was monitored on Culex pipiens quinquefasciatus mosquitoes collected in twelve localities of La Reunion, a geographically isolated island of the Indian Ocean. This mosquito is of medical concern in the region as a known vector for filariasis and a potential vector for West Nile and Rift Valley Fever viruses. Our bioassays indicated the presence of resistance to all tested insecticides, i.e. organochlorides, organophosphates and pyrethroids. A molecular investigation revealed a higher frequency of resistance genes in the coastal areas compared to elevated rural sites, probably reflecting the different nature of insecticide pressures together with the genetic cost of resistance alleles. A simple molecular test was developed to detect Rdl allele, encoding a gamma-aminobutyric acid (GABA) receptor resistant to dieldrin. Unexpectedly high Rdl frequencies were recorded over the whole island, despite this insecticide having been banned for over 15 years. This resistant allele was also detected for the first time in two samples of Aedes albopictus, a species recently involved in severe Chikungunya epidemics on the island. Rdl selection in these two mosquito species discloses current insecticide pressures in urban areas, from unknown origins, that should be taken into account to develop vector control strategies.
ESTHER : Tantely_2010_Insect.Biochem.Mol.Biol_40_317
PubMedSearch : Tantely_2010_Insect.Biochem.Mol.Biol_40_317
PubMedID: 20188834

Title : Malaria vectors in the Republic of Benin: distribution of species and molecular forms of the Anopheles gambiae complex - Djogbenou_2010_Acta.Trop_114_116
Author(s) : Djogbenou L , Pasteur N , Bio-Bangana S , Baldet T , Irish SR , Akogbeto M , Weill M , Chandre F
Ref : Acta Trop , 114 :116 , 2010
Abstract : Members of the Anopheles gambiae complex are among the best malaria vectors in the world, but their vectorial capacities vary between species and populations. A large-scale sampling of An. gambiae sensu lato was carried out in 2006 and 2007 in various bioclimatic areas of Benin (West Africa). The objective of this study was to collate data on the relative frequencies of species and forms within the An. gambiae complex and to produce a map of their spatial distribution. Sampling took place at 30 sites and 2122 females were analyzed. Two species were identified through molecular methods. The overall collection showed a preponderance of An. gambiae s.s., but unexpectedly, An. arabiensis was reported in the coastal-Guinean bioclimatic area characterized by a mean annual rainfall of >1500 mm where only An. gambiae s.s. was reported previously. Our study of Benin indicates that An. arabiensis would be adapted not only to the urban areas but also to the rural humid regions. Among 1717 An. gambiae s.s., 26.5% were of the M form and 73.3% were S form. Few hybrid specimens between the M and S forms were observed (0.2%). Only the spatial distribution of the M form appears to be mainly a function of bioclimatic area. Factors that influence the distribution of these malaria vectors are discussed. This study underlines the need of further investigations of biological, ecological, and behavioral traits of these species and forms to better appreciate their vectorial capacities. Acquisition of entomological field data appears essential to better estimate the stratification of malaria risk and help improve malaria vector control interventions.
ESTHER : Djogbenou_2010_Acta.Trop_114_116
PubMedSearch : Djogbenou_2010_Acta.Trop_114_116
PubMedID: 20138819

Title : Ace-1 duplication in Anopheles gambiae: a challenge for malaria control - Djogbenou_2009_Malar.J_8_70
Author(s) : Djogbenou L , Labbe P , Chandre F , Pasteur N , Weill M
Ref : Malar J , 8 :70 , 2009
Abstract : BACKGROUND: Insecticide resistance is a rapid and recent evolutionary phenomenon with serious economic and public health implications. In the mosquito Anopheles gambiae s.s., main vector of malaria, resistance to organophosphates and carbamates is mainly due to a single amino-acid substitution in acetylcholinesterase 1 (AChE1). This mutation entails a large fitness cost. However, a resistant duplicated allele of the gene encoding AChE1 (ace-1), potentially associated to a lower fitness cost, recently appeared in An. gambiae. METHODS: Using molecular phenotype data collected from natural populations from West Africa, the frequency of this duplicated allele was investigated by statistical inference. This method is based on the departure from Hardy-Weinberg phenotypic frequency equilibrium caused by the presence of this new allele. RESULTS: The duplicated allele, Ag-ace-1(D), reaches a frequency up to 0.65 in Ivory Coast and Burkina Faso, and is potentially present in Benin. A previous study showed that Ag-ace-1(D), present in both M and S molecular forms in different West Africa countries, was generated by a single genetic event. This single origin and its present distribution suggest that this new allele is currently spreading. CONCLUSION: The spread of this less costly resistance allele could represent a major threat to public health, as it may impede An. gambiae control strategies, and thus increases the risk of malaria outbreaks.
ESTHER : Djogbenou_2009_Malar.J_8_70
PubMedSearch : Djogbenou_2009_Malar.J_8_70
PubMedID: 19374767
Gene_locus related to this paper: anoga-ACHE1

Title : Genes conferring resistance to organophosphorus insecticides in Culex pipiens (Diptera: Culicidae) from Tunisia - Ben Cheikh_2009_J.Med.Entomol_46_523
Author(s) : Ben Cheikh R , Berticat C , Berthomieu A , Pasteur N , Ben Cheikh H , Weill M
Ref : Journal of Medical Entomology , 46 :523 , 2009
Abstract : In Tunisia, the mosquito Culex pipiens shows various organophosphate resistance alleles at Ester and ace-1 loci. The characterization and the distribution pattern of these alleles were studied among 20 populations sampled from north to center of Tunisia. At the Ester locus, Ester4, Ester5, and Ester(B12) were present. A new esterase characterized by the same electrophoretic migration as esterase A1 was identified: A13, encoded by Ester(A13) allele. At the ace-1 locus, the presence of the ace-1(R), ace-1(D), and F290V mutated alleles was also detected. A large heterogeneity in allelic frequencies at Ester and ace-1 loci was observed among samples, with a high significant genotypic differentiation considering both loci (F, = 0.077, P < 10(-5)), depicting variations of insecticide treatment intensity between areas. A comparison between populations collected in 1996 and 2005 showed an absence of significant resistance evolution. However, the high frequencies of resistance alleles in 2005 populations suggested that the selection pressures are still important in Tunisia. Strategies for resistance management are discussed in the context of the current knowledge of the Tunisian situation.
ESTHER : Ben Cheikh_2009_J.Med.Entomol_46_523
PubMedSearch : Ben Cheikh_2009_J.Med.Entomol_46_523
PubMedID: 19496423

Title : Multiple duplications of the rare ace-1 mutation F290V in Culex pipiens natural populations - Alout_2009_Insect.Biochem.Mol.Biol_39_884
Author(s) : Alout H , Labbe P , Berthomieu A , Pasteur N , Weill M
Ref : Insect Biochemistry & Molecular Biology , 39 :884 , 2009
Abstract : Two amino acid substitutions in acetylcholinesterase 1 (AChE1), G119S and F290V, are responsible for resistance to organophosphate and carbamate insecticides in Culex pipiens mosquitoes. These mutations generate very different levels of insensitivity to insecticide inhibitors. We described here a biochemical method that rapidly identifies AChE1 variants (susceptible, G119S and F290V, named S, R and V, respectively) present in individual mosquitoes. We investigated the frequency of AChE1 phenotypes in 41 field samples collected around the Mediterranean Sea. F290V substitution was found only in 15 samples and at low frequency, whereas G119S was highly spread in all samples. However, seven V distinct alleles were identified whereas only one R allele was present. The [V] enzymatic phenotype was never observed alone, and the V allele was always found associated with the susceptible and/or G119S AChE1 ([VS], [VR] or [VRS] phenotypes). Furthermore, we showed the presence of duplicated alleles, associating a susceptible and a V copy of the ace-1 gene, in most individuals analyzed for its presence. Evolutionary forces driving the large number of F290V ace-1 alleles and their low frequency in Mediterranean countries are discussed.
ESTHER : Alout_2009_Insect.Biochem.Mol.Biol_39_884
PubMedSearch : Alout_2009_Insect.Biochem.Mol.Biol_39_884
PubMedID: 19874892

Title : Characterization of a novel high-activity esterase in Tunisian populations of the mosquito Culex pipiens - Ben_2008_J.Econ.Entomol_101_484
Author(s) : Ben Cheikh R , Berticat C , Berthomieu A , Pasteur N , Ben Cheikh H , Weill M
Ref : J Econ Entomol , 101 :484 , 2008
Abstract : AIn the mosquito Culex pipiens (L.) (Diptera: Culicidae) esterases contribute to insecticide resistance by their increased activity. These esterases display a heterogeneous geographical distribution, particularly in Tunisia, where they are very diverse. In this study, we extended the characterization of a highly active esterase first detected in 1996: B12. Esterase B12 displayed the fastest electrophoretic mobility of all the previously described highly active esterases. We showed that it was encoded by the Ester(B12) allele at the Ester locus, and we isolated a strain, TunB12, homozygous for this allele. TunB12 displayed a low (approximately two- to three-fold) but significant resistance to the organophosphates temephos and chlorpyrifos, and to the pyrethroid permethrin. Only temephos resistance was synergized by S,S,S-tributyl-phosphorotrithioate. Real-time quantitative polymerase chain reaction revealed that the Ester(B12) allele was not amplified in TunB12 strain, indicating that B12 high activity could be due to a gene up-regulation mechanism. Ester(B12) allele frequencies also were estimated in 20 Tunisian populations collected in 2005. Analyses revealed a large distribution of this allele all over the country. Finally, sequences of Ester(B12) were acquired and genetic distance trees were constructed with the resistance Ester alleles already published, providing indications about allele's origins. The diverse array of highly active esterases in C. pipiens from Tunisia and the possible scenario of the origin of their coding alleles are discussed in the context of their possible evolution.
ESTHER : Ben_2008_J.Econ.Entomol_101_484
PubMedSearch : Ben_2008_J.Econ.Entomol_101_484
PubMedID: 18459415

Title : Evolution of resistance under insecticide selection pressure in Culex pipiens quinquefasciatus (Diptera, Culicidae) from Martinique - Yebakima_2004_J.Med.Entomol_41_718
Author(s) : Yebakima A , Marquine M , Rosine J , Yp-Tcha MM , Pasteur N
Ref : Journal of Medical Entomology , 41 :718 , 2004
Abstract : Population surveys of Culex pipiens quinquefasciatus carried out in 1991 and 1999 were compared with data collected in 1990 before the beginning of the control program against this mosquito. Larval samples collected in 1999 displayed resistance to the four tested insecticides: permethrin, propoxur, temephos, and chlorpyrifos. Temephos resistance ratio at LC50 (RR50) ranged between 8.1- and 42-fold compared with 2.9- and 4.6-fold in 1990, and chlorpyrifos RR50 ranged between 8.6- and 123-fold compared with 6.4- and 19-fold in 1990. This increased resistance to organophosphorus insecticides was associated with a sharp decrease of susceptible genotypes at two loci (Ester and ace-1), as well as to an allele replacement at the Ester locus.
ESTHER : Yebakima_2004_J.Med.Entomol_41_718
PubMedSearch : Yebakima_2004_J.Med.Entomol_41_718
PubMedID: 15311466

Title : Insecticide resistance: a silent base prediction -
Author(s) : Weill M , Berthomieu A , Berticat C , Lutfalla G , Negre V , Pasteur N , Philips A , Leonetti JP , Fort P , Raymond M
Ref : Current Biology , 14 :R552 , 2004
PubMedID: 15268871

Title : Comparative genomics: Insecticide resistance in mosquito vectors - Weill_2003_Nature_423_136
Author(s) : Weill M , Lutfalla G , Mogensen K , Chandre F , Berthomieu A , Berticat C , Pasteur N , Philips A , Fort P , Raymond M
Ref : Nature , 423 :136 , 2003
Abstract : Resistance to insecticides among mosquitoes that act as vectors for malaria (Anopheles gambiae) and West Nile virus (Culex pipiens) emerged more than 25 years ago in Africa, America and Europe; this resistance is frequently due to a loss of sensitivity of the insect's acetylcholinesterase enzyme to organophosphates and carbamates1. Here we show that this insensitivity results from a single amino-acid substitution in the enzyme, which we found in ten highly resistant strains of C. pipiens from tropical (Africa and Caribbean) and temperate (Europe) areas, as well as in one resistant African strain of A. gambiae. Our identification of this mutation may pave the way for designing new insecticides.
ESTHER : Weill_2003_Nature_423_136
PubMedSearch : Weill_2003_Nature_423_136
PubMedID: 12736674
Gene_locus related to this paper: anoga-ACHE1 , culpi-ACHE1

Title : A novel acetylcholinesterase gene in mosquitoes codes for the insecticide target and is non-homologous to the ace gene Drosophila - Weill_2002_Proc.R.Soc.Lond.B.Biol.Sci_269_2007
Author(s) : Weill M , Fort P , Berthomieu A , Dubois MP , Pasteur N , Raymond M
Ref : Proc R Soc Lond B Biol Sci , 269 :2007 , 2002
Abstract : Acetylcholinesterase (AChE) is the target of two major insecticide families, organophosphates (OPs) and carbamates. AChE insensitivity is a frequent resistance mechanism in insects and responsible mutations in the ace gene were identified in two Diptera, Drosophila melanogaster and Musca domestica. However, for other insects, the ace gene cloned by homology with Drosophila does not code for the insensitive AChE in resistant individuals, indicating the existence of a second ace locus. We identified two AChE loci in the genome of Anopheles gambiae, one (ace-1) being a new locus and the other (ace-2) being homologous to the gene previously described in Drosophila. The gene ace-1 has no obvious homologue in the Drosophila genome and was found in 15 mosquito species investigated. In An. gambiae, ace-1 and ace-2 display 53% similarity at the amino acid level and an overall phylogeny indicates that they probably diverged before the differentiation of insects. Thus, both genes are likely to be present in the majority of insects and the absence of ace-1 in Drosophila is probably due to a secondary loss. In one mosquito (Culex pipiens), ace-1 was found to be tightly linked with insecticide resistance and probably encodes the AChE OP target. These results have important implications for the design of new insecticides, as the target AChE is thus encoded by distinct genes in different insect groups, even within the Diptera: ace-2 in at least the Drosophilidae and Muscidae and ace-1 in at least the Culicidae. Evolutionary scenarios leading to such a peculiar situation are discussed.
ESTHER : Weill_2002_Proc.R.Soc.Lond.B.Biol.Sci_269_2007
PubMedSearch : Weill_2002_Proc.R.Soc.Lond.B.Biol.Sci_269_2007
PubMedID: 12396499
Gene_locus related to this paper: aedae-ACHE1 , anoga-ACHE1 , anoga-ACHE2 , cioin-ACHE1 , ciosa-ACHE , culpi-ACHE1

Title : Mechanisms of resistance to organophosphates in Tetranychus urticae (Acari: Tetranychidae) from Greece - Tsagkarakou_2002_Insect.Biochem.Mol.Biol_32_417
Author(s) : Tsagkarakou A , Pasteur N , Cuany A , Chevillon C , Navajas M
Ref : Insect Biochemistry & Molecular Biology , 32 :417 , 2002
Abstract : We investigated the mechanisms conferring resistance to methyl-parathion (44-fold) and to methomyl (8-fold) in Tetranychus urticae from Greece by studying the effect of synergists on the resistance and the kinetic characteristics of various enzymes in a resistant strain (RLAB) and a susceptible reference strain (SAMB). It is shown that S,S,S-tributyl phosphorotrithioate, a synergist that inhibits esterases and glutathione S-transferases, and piperonyl butoxide, a synergist that inhibits cytochrome P450 mediated monooxygenases, did not affect the level of methyl-parathion or methomyl resistance in RLAB and that resistance ratios to both insecticides did not change significantly in the presence of either synergist. Isoelectric focusing of esterase allozymes on single mites revealed no differences in staining intensity and glutathione S-transferase activity was not significantly different in the two strains. The activity of two cytochrome P450 monooxygenase groups was compared. No significant difference of 7-ethoxyresorufin-O-diethylase activity was observed between strains that were two-fold higher in RLAB than in SAMB. The kinetic characteristics of acetylcholinesterase, the target enzyme of organophosphates and carbamates, revealed that acetylcholinesterase in RLAB was less sensitive to inhibition by paraoxon and methomyl in comparison with SAMB. I(50), the inhibitor concentration inducing 50% decrease of acetylcholinesterase activity was greater (119- and 50-fold with paraoxon and methomyl, respectively) and the bimolecular constant k(i) was lower (39- and 47-fold with paraoxon and methomyl, respectively) in RLAB compared to SAMB.
ESTHER : Tsagkarakou_2002_Insect.Biochem.Mol.Biol_32_417
PubMedSearch : Tsagkarakou_2002_Insect.Biochem.Mol.Biol_32_417
PubMedID: 11886776

Title : Tissue localization of overproduced esterases in the mosquito Culex pipiens (Diptera: Culicidae) - Pasteur_2001_J.Med.Entomol_38_791
Author(s) : Pasteur N , Nance E , Bons N
Ref : Journal of Medical Entomology , 38 :791 , 2001
Abstract : We have investigated the tissue distribution of overproduced esterases A (A1 and A2) and B (B1 and B2) in strains of Culex pipiens L. by immunocytochemistry. S-LAB mosquitoes, lacking overproduced esterases, were used as reference. Tissues showing a strong specific reaction (fluorescence) were observed with anti-esterase A1 antiserum in S54 (with A1) and BOUAKE (with A2) strains, and with anti-esterase B1 antiserum in TEM-R and EDIT (with B1) and BOUAKE (with B2) strains. Overproduction of esterases A and B was tissue-specific. The most constant pattern for the two types of esterases was their overproduction in the alimentary canal and Malpighian tubes, although fluorescence varied in intensity depending on strains and developmental stages. There was no difference in the tissue distribution of esterases Al and A2. In contrast, esterases B pattern was highly variable among strains. Differences between TEM-R and EDIT were explained by the different overall overproduction and number of copies of the amplified gene (10-fold higher in TEM-R). The most striking difference in esterase B1 and B2 tissue localization concerned the nervous system where neurons were intenisely fluorescent in TEM-R and EDIT (B1), but not in BOUAKE (B2). All esterase B positive tissues in TEM-R contained large quantities of esterase B1 mRNA (in situ hybridization), indicating that at least part of the protein revealed by immunochemistry was produced in the tissues where it was observed. Our results are discussed in terms of the protection that the different esterases can confer during exposition to organophosphorous insecticides.
ESTHER : Pasteur_2001_J.Med.Entomol_38_791
PubMedSearch : Pasteur_2001_J.Med.Entomol_38_791
PubMedID: 11761376

Title : Insecticide resistance in the mosquito culex pipiens: what have we learned about adaptation? - Raymond_2001_Genetica_112-113_287
Author(s) : Raymond M , Berticat C , Weill M , Pasteur N , Chevillon C
Ref : Genetica , 112-113 :287 , 2001
Abstract : Resistance to organophosphate (OP) insecticide in the mosquito Culex pipiens has been studied for ca. 30 years. This example of micro-evolution has been thoroughly investigated as an opportunity to assess precisely both the new adapted phenotypes and the associated genetic changes. A notable feature is that OP resistance is achieved with few genes, and these genes have generally large effects. The molecular events generating such resistance genes are complex (e.g., gene amplification, gene regulation) potentially explaining their low frequency of de novo occurrence. In contrast, migration is a frequent event, including passive transportation between distant populations. This generates a complex interaction between mutations and migration, and promotes competition among resistance alleles. When the precise physiological action of each gene product is rather well known, it is possible to understand the dominance level or the type of epistasis observed. It is however difficult to predict a priori how resistance genes will interact, and it is too early to state whether or not this will be ever possible. These resistance genes are costly, and the cost is variable among them. It is usually believed that the initial fitness cost would gradually decrease due to subsequent mutations with a modifier effect. In the present example, a particular modifier occurred (a gene duplication) at one resistance locus, whereas at the other one reduction of cost is driven by allele replacement and apparently not by selection of modifiers.
ESTHER : Raymond_2001_Genetica_112-113_287
PubMedSearch : Raymond_2001_Genetica_112-113_287
PubMedID: 11838771

Title : Overproduced esterases in Culex pipiens quinquefasciatus (Diptera: Culicidae) from Vietnam - Pasteur_2001_J.Med.Entomol_38_740
Author(s) : Pasteur N , Marquine M , Hoang TH , Nam VS , Failloux AB
Ref : Journal of Medical Entomology , 38 :740 , 2001
Abstract : The electrophoretic polymorphism of loci encoding for 10 enzymes was studied in Culex p. quinquefasciatus Say from six localities of Vietnam. The analysis of 11 "neutral genes" showed that differentiation among samples was low, but significant (Fst = 0.06), and significantly related to geographic distance between sample sites. These results are similar to those observed in other countries (Europe and west Africa). A single type of overproduced esterases (A2-B2) was observed, and its frequency was high (60-100%) in all samples. This situation is in sharp contrast with that observed in other countries of South East Asia (China, South Korea and Japan), where two or more types of overproduced esterases have been reported. A map summarizing the geographic distribution of Asian Cr. p. quinquefasciatus with overproduced esterases is provided.
ESTHER : Pasteur_2001_J.Med.Entomol_38_740
PubMedSearch : Pasteur_2001_J.Med.Entomol_38_740
PubMedID: 11580049

Title : The kdr mutation occurs in the Mopti form of Anopheles gambiae s.s. through introgression - Weill_2000_Insect.Mol.Biol_9_451
Author(s) : Weill M , Chandre F , Brengues C , Manguin S , Akogbeto M , Pasteur N , Guillet P , Raymond M
Ref : Insect Molecular Biology , 9 :451 , 2000
Abstract : Anopheles gambiae s.s. is a complex of sibling taxa characterized by various paracentric inversions. In west and central Africa, where several taxa are sympatric, a kdr mutation responsible for pyrethroid resistance has been described in only one (the S taxon), suggesting an absence of gene flow between them. Following a thorough sampling, we have found a kdr mutation in another taxon (M). To establish whether this mutation is the same event or not, the large intron upstream of the kdr mutation was sequenced to find polymorphic sites in susceptible/resistant and M/S mosquitoes. The low genetic diversity found in this DNA region indicates that a local genetic sweep has recently occurred. However, some polymorphic sites were found, and it is therefore concluded that the kdr mutation in the M taxon is not an independent mutation event, and is best explained by an introgression from the S taxon. These results are discussed within the context of possible gene flow between members of An. gambiae s.s. taxa, and with the possible spread of the kdr mutation in other closely related malaria vectors of the An. gambiae complex.
ESTHER : Weill_2000_Insect.Mol.Biol_9_451
PubMedSearch : Weill_2000_Insect.Mol.Biol_9_451
PubMedID: 11029663

Title : A new mechanism conferring unprecedented high resistance to chlorpyrifos in Culex pipiens (Diptera: Culicidae) - Pasteur_1999_J.Med.Entomol_36_794
Author(s) : Pasteur N , Marquine M , Ben Cheikh H , Bernard C , Bourguet D
Ref : Journal of Medical Entomology , 36 :794 , 1999
Abstract : The cause of high resistance to chlorpyrifos observed in Tunisian Culex pipiens (L.) was investigated by comparing a Tunisian strain G (> 10,000-fold resistance), a French strain T (approximately 50-fold resistance), and a susceptible reference strain S. Strains G and T had the same level of propoxur resistance (approximately 1,000-fold) and were homozygous for an autosomal propoux-insensitive acetylcholinesterase (AChE-1). In G and T strains, as well as in the offspring of different F1s and backcrosses using these F1s and the S strain, the effect of DEF and Pb synergists on chlorpyrifos resistance was low or absent, indicating that increased detoxification by enzymes inhibited by these chemicals had a minor role. Chlorpyrifos resistance in the G strain was caused by a major gene (or group of genes) tightly linked to the Ace-1 gene (coding AChE-1 enzyme). The possibility of allelism between this gene and the Ace-1R allele present in the T strain was rejected by showing that AChE-1 inhibition by chlorpyrifos-oxon was not different between G and T mosquitoes.
ESTHER : Pasteur_1999_J.Med.Entomol_36_794
PubMedSearch : Pasteur_1999_J.Med.Entomol_36_794
PubMedID: 10593083

Title : Mechanisms of insecticide resistance in the aphid Nasonovia ribisnigri (Mosley) (Homoptera: Aphididae) from France - Rufingier_1999_Insect.Biochem.Mol.Biol_29_385
Author(s) : Rufingier C , Pasteur N , Lagnel J , Martin C , Navajas M
Ref : Insect Biochemistry & Molecular Biology , 29 :385 , 1999
Abstract : Nasonovia ribisnigri, a main pest of salad crops, has developed resistance to various insecticides in southern France, including the carbamate pirimicarb and the cyclodiene endosulfan, two insecticides widely used to control this aphid. Here we have investigated the mechanisms of resistance to these two insecticides by studying cross-resistance, synergism, activity of detoxifying enzymes, and possible modifications of the target proteins. Resistance to pirimicarb was shown to be mainly due to a decreased sensitivity of the target acetylcholinesterase; this modification conferred also, resistance to propoxur but not to methomyl and the two tested organophosphates (acephate and paraoxon). Endosulfan resistance was associated with a moderate level of resistance to dieldrin, and resistance to both insecticides was due, in part, to increased detoxification by glutathione S-transferases (GST). The endosulfan resistant strain displayed the same amino acid at position 302 of the Rdl gene (GABA receptor) as susceptible aphids (e.g. Ala), indicating that the Ala to Ser (or to Gly) mutation observed among dieldrin resistant strains of other insect species was not present.
ESTHER : Rufingier_1999_Insect.Biochem.Mol.Biol_29_385
PubMedSearch : Rufingier_1999_Insect.Biochem.Mol.Biol_29_385
PubMedID: 10333576

Title : Voltage-dependent Na+ channels in pyrethroid-resistant Culex pipiens L mosquitoes - Martinez-Torres_1999_Pest.Sci_55_1012
Author(s) : Martinez-Torres D , Chevillon C , Brun-Barale A , Berge J , Pasteur N , Pauron D
Ref : Pest Sci , 55 :1012 , 1999
Abstract : In some insect species, knockdown resistance (kdr) to pyrethroids and DDT is linked to point mutations in the sequence of the para-type voltage-dependent sodium channel gene. The effects of pyrethroids were assayed on six Culex pipiens strains: two were susceptible to pyrethroids and the four others displayed various levels of resistance, but, in each case, a kdr-type mechanism was strongly suggested. Degenerate primers were designed on the basis of the corresponding sequences of the para orthologous gene reported from several orders of insects. These primers were used to amplify the region of the sodium channel gene which includes the positions where the kdr and super-kdr mutations have been found in Musca domestica. As expected, the amplified fragment was highly homologous to the para sequences. The super-kdr-like mutation (methionine to threonine at position 918 of the M domestica para sequence) was never detected in any strain. In contrast, the same kdr mutation (leucine to phenylalanine at position 1014) was present in some Culex pyrethroid-resistant samples. An alternative substitution of the same leucine to a serine was detected in one strain slightly resistant to pyrethroids but highly resistant to DDT. These data have allowed us to design a PCR-based diagnostic test on genomic DNA to determine the presence or the absence of the kdr allele in single C pipiens collected in several countries. The validity of this test was checked by comparing the frequency of the resistance allele and the toxicological data.
ESTHER : Martinez-Torres_1999_Pest.Sci_55_1012
PubMedSearch : Martinez-Torres_1999_Pest.Sci_55_1012

Title : A new esterase gene amplification involved in OP resistance in Culex pipiens mosquitoes from China - Qiao_1998_Biochem.Genet_36_417
Author(s) : Qiao CL , Marquine M , Pasteur N , Raymond M
Ref : Biochemical Genetics , 36 :417 , 1998
Abstract : Two overproduced esterases (A8 and B8) not previously described were found in southern China. They provide a low resistance level to organophosphate (OP) insecticides, and correspond to a coamplification of both esterase loci (Est-2 and Est-3) classically involved in OP resistance for this mosquito species. This coamplification is distinct from all other similar events thus far reported. The peculiar situation in southern China, where numerous OP resistance alleles at these two loci were found, is discussed in comparison with the Mediterranean situation, the only one with a similar diversity of overproduced esterases.
ESTHER : Qiao_1998_Biochem.Genet_36_417
PubMedSearch : Qiao_1998_Biochem.Genet_36_417
PubMedID: 10230522

Title : Molecular characterization of pyrethroid knockdown resistance (kdr) in the major malaria vector Anopheles gambiae s.s - Martinez-Torres_1998_Insect.Mol.Biol_7_179
Author(s) : Martinez-Torres D , Chandre F , Williamson MS , Darriet F , Berge JB , Devonshire AL , Guillet P , Pasteur N , Pauron D
Ref : Insect Molecular Biology , 7 :179 , 1998
Abstract : Pyrethroid-impregnated bednets are playing an increasing role for combating malaria, especially in stable malaria areas. More than 90% of the current annual malaria incidence (c. 500 million clinical cases with up to 2 million deaths) is in Africa where the major vector is Anopheles gambiae s.s. As pyrethroid resistance has been reported in this mosquito, reliable and simple techniques are urgently needed to characterize and monitor this resistance in the field. In insects, an important mechanism of pyrethroid resistance is due to a modification of the voltage-gated sodium channel protein recently shown to be associated with mutations of the para-type sodium channel gene. We demonstrate here that one of these mutations is present in certain strains of pyrethroid resistant A. gambiae s.s. and describe a PCR-based diagnostic test allowing its detection in the genome of single mosquitoes. Using this test, we found this mutation in six out of seven field samples from West Africa, its frequency being closely correlated with survival to pyrethroid exposure. This diagnostic test should bring major improvement for field monitoring of pyrethroid resistance, within the framework of malaria control programmes.
ESTHER : Martinez-Torres_1998_Insect.Mol.Biol_7_179
PubMedSearch : Martinez-Torres_1998_Insect.Mol.Biol_7_179
PubMedID: 9535162

Title : A sex-linked Ace gene, not linked to insensitive acetylcholinesterase- mediated insecticide resistance in Culex pipiens - Malcolm_1998_Insect.Mol.Biol_7_107
Author(s) : Malcolm CA , Bourguet D , Ascolillo A , Rooker SJ , Garvey CF , Hall LM , Pasteur N , Raymond M
Ref : Insect Molecular Biology , 7 :107 , 1998
Abstract : An acetylcholinesterase (AChE) gene, Ace.x, showing 93% identity of deduced amino acid sequence to Anopheles stephensi Ace has been cloned from a Culex pipiens strain homozygous for insensitive AChE (iAChE) mediated insecticide resistance. DNA sequence of genomic DNA clones identified exons 2-5. RFLP of six clones indicated four possible alleles. Linkage analysis located Ace.x to chromosome I, less than 0.8 centimorgans from the sex locus, whereas the locus conferring resistance was 2.0 centimorgans from plum-eye on chromosome II. Ace.1 coding for AChE1, which is associated with resistance, is therefore autosomal. We propose that Ace.x is the recently postulated Ace.2 coding for the biochemically distinct AChE2, which is not associated with resistance.
ESTHER : Malcolm_1998_Insect.Mol.Biol_7_107
PubMedSearch : Malcolm_1998_Insect.Mol.Biol_7_107
PubMedID: 9535157
Gene_locus related to this paper: culpi-ACHE2

Title : Resistance to organophosphorus and pyrethroid insecticides in Culex pipiens (Diptera: Culicidae) from Tunisia - Ben Cheikh_1998_J.Med.Entomol_35_251
Author(s) : Ben Cheikh H , Ben Ali-Haouas Z , Marquine M , Pasteur N
Ref : Journal of Medical Entomology , 35 :251 , 1998
Abstract : Resistance to the organophosphates temephos and chlorpyrifos, the carbamate propoxur, the pyrethroid permethrin, and the organochloride DDT was investigated in Tunisian populations of Culex pipiens pipiens (L.) collected between 1990 and 1996. Resistance to temephos was uniformly low, reaching 10-fold in the most resistant population. In contrast, resistance to chlorpyrifos was highly variable, reaching the highest level (> 10,000-fold) recorded worldwide. The chlorpyrifos-resistant populations also were highly resistant to propoxur. Some populations also showed high resistance to permethrin (up to 5,000-fold) and moderate resistance to DDT (approximately 20-fold). Bioassays conducted in the presence of synergists showed that increased detoxification had only a minor role in resistance, although several over-produced esterases known to be involved in organophosphate resistance were detected. To better understand the factors influencing the distribution of resistance in Tunisia, the polymorphism of genes involved in organophosphate resistance (i.e., over-produced esterases and insensitive acetylcholinesterase) was investigated in relation to the genetic structure of populations studied by analyzing the electrophoretic polymorphism of "neutral" genes. Over the area studied, and despite a high level of gene flow, resistance genes showed a patchy distribution. Results are discussed in relation to the selection pressure caused by insecticide treatments.
ESTHER : Ben Cheikh_1998_J.Med.Entomol_35_251
PubMedSearch : Ben Cheikh_1998_J.Med.Entomol_35_251
PubMedID: 9615543

Title : Cross-resistance to pyrethroid and organophosphorus insecticides in the southern house mosquito (Diptera:Culicidae) from Cuba - Bisset_1997_J.Med.Entomol_34_244
Author(s) : Bisset J , Rodriguez M , Soca A , Pasteur N , Raymond M
Ref : Journal of Medical Entomology , 34 :244 , 1997
Abstract : A sample of the southern house mosquito, Culex pipiens quinquefasciatus Say, from Cuba was subjected to lambda-cyhalothrin selection to evaluate the usefulness of this pyrethroid insecticide for mosquito control. High resistance developed after 6 generations of selection. Little or no cross-resistance was observed to other pyrethroids (deltamethrin and cypermethrin), to a carbamate (propoxur) and to some organophosphates (chlorpyrifos and pirimiphos-methyl), but high cross-resistance was found to malathion (organophosphate). Possible resistance mechanisms responsible for this phenomenon are discussed.
ESTHER : Bisset_1997_J.Med.Entomol_34_244
PubMedSearch : Bisset_1997_J.Med.Entomol_34_244
PubMedID: 9103771

Title : Pleiotropy of adaptive changes in populations: comparisons among insecticide resistance genes in Culex pipiens - Chevillon_1997_Genet.Res_70_195
Author(s) : Chevillon C , Bourguet D , Rousset F , Pasteur N , Raymond M
Ref : Genetical Research , 70 :195 , 1997
Abstract : Resistance to toxicants is a convenient model for investigating whether adaptive changes are associated with pleiotropic fitness costs. Despite the voluminous literature devoted to this subject, intraspecific comparisons among toxicant resistance genes are rare. We report here results on the pleiotropic effect on adult survival of Culex pipiens mutants involved in the same adaptation: the resistance to organophosphorus insecticides. This field study was performed in southern France where four resistance genes sequentially appeared and increased in frequency in response to intense insecticide control. By repeated sampling of overwintering females through winter, we analysed the impact of each of three resistance genes on adult survival. We showed that (i) the most recent gene seems to be of no disadvantage during winter, (ii) the oldest affects survival in some environmental conditions, and (iii) the third induces a constant, severe and dominant survival cost. Such variability is discussed in relation to the physiological changes involved in resistance.
ESTHER : Chevillon_1997_Genet.Res_70_195
PubMedSearch : Chevillon_1997_Genet.Res_70_195
PubMedID: 9494436

Title : Distribution of organophosphate and carbamate resistance in Culex pipiens quinquefasciatus (Diptera: Culicidae) in West Africa - Chandre_1997_J.Med.Entomol_34_664
Author(s) : Chandre F , Darriet F , Doannio JM , Riviere F , Pasteur N , Guillet P
Ref : Journal of Medical Entomology , 34 :664 , 1997
Abstract : The distribution of organophosphate and carbamate resistance was investigated in 33 samples of Culex pipiens quinquefasciatus Say from 25 cities in Cte d'Ivoire and Burkina Faso. Organophosphate resistance levels were higher in Cte d'Ivoire than in Burkina Faso. Chlorpyrifos resistance ratios at LC95 ranged from 4 to 30 times in Cte d'Ivoire and from 3 to 6 times in Burkina Faso. For temephos, ratios ranged from 3 to 18 and from 1 to 2, respectively. Of 27 samples from Cte d'Ivoire, 25 also displayed cross resistance to carbamates as shown by a mortality plateau in bioassays with propoxur and carbosulfan (similar to chlorpyrifos). Cross resistance to organophosphates and carbamates was caused by an insensitive acetylcholinesterase allele (AceR). This gene was absent from Burkina Faso, except in Niangoloko near the Cte d'Ivoire border. Organophosphate resistance also was associated with the presence of A2-B2 overproduced esterases which had higher frequencies in Cte d'Ivoire (75-100%) than in Burkina Faso (40-50%). Two other esterases with the same electrophoretic mobility as C2 from Puerto Rico and B1 from California were identified for the 1st time in West Africa. "C2" was widespread, whereas "B1" was present in only a few mosquitoes from Cte d'Ivoire. These differences in resistance patterns should be taken into consideration in planning urban mosquito control strategies within 2 countries.
ESTHER : Chandre_1997_J.Med.Entomol_34_664
PubMedSearch : Chandre_1997_J.Med.Entomol_34_664
PubMedID: 9439121

Title : Insecticide resistance genes in mosquitoes: their mutations, migration, and selection in field populations. - Pasteur_1996_J.Hered_87_444
Author(s) : Pasteur N , Raymond M
Ref : Journal of Heredity , 87 :444 , 1996
Abstract : Insecticides have been used intensively to control insect populations over the last 50 years and many species of insects have developed resistance to several families of insecticides. These resistances are mainly due to two mechanisms: mutation of the insecticide target protein (leading to a decrease in its affinity for the concerned insecticide family), and increased detoxification. Recent molecular studies suggest that the mutations conferring resistance are rare and sometimes unique events in any given species. The wide geographic distribution of some of these genes can then only be explained by the balance between migration and selection at the population level.
ESTHER : Pasteur_1996_J.Hered_87_444
PubMedSearch : Pasteur_1996_J.Hered_87_444
PubMedID: 8981762

Title : Duplication of the Ace.1 locus in Culex pipiens mosquitoes from the Caribbean - Bourguet_1996_Biochem.Genet_34_351
Author(s) : Bourguet D , Raymond M , Bisset J , Pasteur N , Arpagaus M
Ref : Biochemical Genetics , 34 :351 , 1996
Abstract : In Culex pipiens mosquitoes, AChE1 encoded by the locus Ace.1 is the target of organophosphorus and carbamate insecticides. In several resistant strains homozygous for Ace.1RR, insensitive AChE1 is exclusively found. An unusual situation occurs in two Caribbean resistant strains where each mosquito, at each generation, displays a mixture of sensitive and insensitive AChE1. These mosquitoes are not heterozygotes, Ace.1RS, as preimaginal mortalities cannot account for the lethality of both homozygous classes. This situation is best explained by the existence of two Ace.1 loci, coding, respectively, a sensitive and an insensitive AChE1. Thus, we suggest that in the Caribbean a duplication of the Ace.1 locus occurred before the appearance of insecticide resistance at one of the two copies.
ESTHER : Bourguet_1996_Biochem.Genet_34_351
PubMedSearch : Bourguet_1996_Biochem.Genet_34_351
PubMedID: 8978907

Title : Coamplification of esterase A and B genes as a single unit in Culex pipiens misquitos - Rooker_1996_Heredity_77_555
Author(s) : Rooker S , Guillema T , Berge JB , Pasteur N , Raymond M
Ref : Heredity , 77 (5) :555 , 1996
Abstract : In Culex pipiens mosquitoes, resistance to organophosphorous insecticides often results from increased detoxification by two types of esterases, A and B, which are closely linked. Overproduction of all esterase B so far investigated (B1, B2, B4, B5 and B6) is from gene amplification. An esterase A gene (esterase A2) has recently been cloned from mosquitoes with the overproduced esterases A2 and B2, and amplification of this gene has also been reported. We describe the cDNA sequences of three additional esterase genes from insecticide-resistant strains of Culex pipiens originating from France and California which show at least 93 per cent homology with the esterase A2 gene sequence. Restriction enzyme mapping shows that the esterase A gene lies within 2.2 kb of the esterase B gene. In mosquitoes with overproduced esterases A2 and B2, the amplification level of esterase A is equal to that of esterase B suggesting that the genes are coamplified. Furthermore, we show that in one strain with an overproduced A esterase (A1), gene amplification cannot account for the increased protein level. This indicates that overproduction of esterases A can be achieved through two different mechanisms: gene amplification and a regulatory mechanism--the nature of which remains to be identified.
ESTHER : Rooker_1996_Heredity_77_555
PubMedSearch : Rooker_1996_Heredity_77_555
PubMedID: 8939022
Gene_locus related to this paper: culpi-ESTA

Title : Determination of Ace.1 Genotypes in Single Mosquitoes: Toward an Ecumenical Biochemical Test - Bourguet_1996_Pestic.Biochem.Physiol_55_122
Author(s) : Bourguet D , Pasteur N , Bisset J , Raymond M
Ref : Pestic Biochem Physiol , 55 :122 , 1996
Abstract : The occurrence of two acetylcholinesterases, AChE1 and AChE2, in the mosquito Culex pipiens has been recently documented. Resistance to organophosphates and carbamates due to target insensitivity is the result of a qualitative change of only AChE1, encoded by the Ace.1 gene. Because AChE1 and AChE2 differ in their sensitivity to inhibitors, Ace.1 genotypes can be misclassified by previous tests. We describe a new rapid microplate test that allows unambiguous identification of Ace.1 genotypes. This test involves comparing AChE activities in the absence of insecticide and in the presence of two propoxur concentrations: a low concentration that inhibits only the sensitive AChE1 and a higher concentration that inhibits also AChE2 but not the insensitive AChE1 responsible of insecticide resistance. This comparison allows the identification of the three Ace.1 genotypes: resistant (Ace.1RR), susceptible (Ace.1SS) homozygotes, and heterozygotes (Ace.1RS). The similarity of propoxur sensitivity of modified AChE1s found in various resistant strains from the United States, Europe, and Africa indicates that this test is probably suitable for all the Ace.1 alleles described so far in C. pipiens.
ESTHER : Bourguet_1996_Pestic.Biochem.Physiol_55_122
PubMedSearch : Bourguet_1996_Pestic.Biochem.Physiol_55_122
PubMedID: 8980036

Title : Resistance to organophosphorous insecticides in Culex pipiens quinquefasciatus (Diptera: Culicidae) from Martinique - Yebakima_1995_J.Med.Entomol_32_77
Author(s) : Yebakima A , Raymond M , Marquine M , Pasteur N
Ref : Journal of Medical Entomology , 32 :77 , 1995
Abstract : Before beginning a widespread control program against Culex pipiens quinquefasciatus in Martinique, resistance to temephos, chlorpyrifos, and two organophosphorous insecticides, was investigated at seven breeding sites. At LC95, populations exhibited resistance ratios between 6.9 and 11.6 for temephos and between 6.4 and 51.4 for chlorpyrifos. Overproduced esterases A2-B2 and B1, known to be involved in organophosphorous-resistance, were present at all breeding sites; esterases A2-B2 frequency was > 50% at all sites but one; and esterase B1 frequency was < 7%. Experimental treatment of three breeding sites with temephos induced no significant increase in resistance, but our esterase studies indicated a significant increase in the frequencies of esterase B1 and of a new highly active esterase C2. These results indicate that a large-scale C. p. quinquefasciatus control program with organophosphorous insecticides will induce a rapid increase of these resistance genes throughout Martinique. However, this may not necessarily result in high levels of resistance, because, at present, the level of gene amplification of esterase B still appears to be low.
ESTHER : Yebakima_1995_J.Med.Entomol_32_77
PubMedSearch : Yebakima_1995_J.Med.Entomol_32_77
PubMedID: 7541837

Title : Resistance monitoring in Culex pipiens (Diptera: Culicidae) from central-eastern France - Rivet_1994_J.Med.Entomol_31_231
Author(s) : Rivet Y , Raymond M , Rioux JA , Delalbre A , Pasteur N
Ref : Journal of Medical Entomology , 31 :231 , 1994
Abstract : Insensitive acetylcholinesterase (AceR) and five over-produced esterases (A1, A2 and B2, and A4 and B4) involved in detoxification are responsible for resistance to organophosphorous insecticides (OPs) in Culex pipiens L. from the Rhne-Alpes region, where C. pipiens control is mainly accomplished with the OPs temephos and chlorpyrifos using 0.15 mg/liter doses. The strong linkage disequilibria observed between esterases A1 and Est-20(0.64), esterases A4 and B4, and esterases A2 and B2 indicate that these genes were introduced in the Rhne-Alpes region. AceR and esterase A1, which appeared in the south of France 3 yr before the start of mosquito control in Rhne-Alpes, had the highest frequencies. All resistant genotypes were shown to be killed by 0.15 mg/liter temephos in natural breeding sites, but not by 0.15 mg/liter chlorpyrifos. These results are discussed in relation with mosquito control strategies.
ESTHER : Rivet_1994_J.Med.Entomol_31_231
PubMedSearch : Rivet_1994_J.Med.Entomol_31_231
PubMedID: 7514668

Title : Insecticide susceptibility in mosquitoes (Diptera: Culicidae) from French Polynesia - Failloux_1994_J.Med.Entomol_31_639
Author(s) : Failloux AB , Ung A , Raymond M , Pasteur N
Ref : Journal of Medical Entomology , 31 :639 , 1994
Abstract : Susceptibility to six organophosphate (OP), two pyrethroid (PY), and one carbamate (C) insecticides was investigated in Culex pipiens quinquefasciatus Say, Aedes aegypti (L.), and Aedes polynesiensis Marks larvae from the island of Tahiti. Cx. p. quinquefasciatus and Ae. aegypti were compared with susceptible reference strains treated simultaneously. A low, but significant, resistance to bromophos (4.6x), chlorpyrifos (5.7x), fenthion (2.4x), fenitrothion (5.0x), temephos (4.3x) and permethrin (2.1x) was found in Cx. p. quinquefasciatus, and to malathion (1.5x), temephos (2.3x), permethrin (1.8x) and propoxur (1.7x) in Ae. aegypti. Cx. p. quinquefasciatus was shown to possess over-produced esterases A2 and B2, which are known to be involved in resistance to OPs in other countries. Ae. polynesiensis was less resistant than the Ae. aegypti reference strain to all insecticides except temephos (1.8x) and permethrin (6.7x). To determine whether Ae. polynesiensis had developed resistance to these insecticides in Tahiti, a geographical survey covering 12 islands of the Society, Tuamotu, Tubuai, Marquesas, and Gambier archipelagoes was undertaken with three insecticides (temephos, deltamethrin, and permethrin). Two- to threefold variations in LC50S were observed among collections. Results are discussed in relationship to the level of insecticide exposure on the different islands.
ESTHER : Failloux_1994_J.Med.Entomol_31_639
PubMedSearch : Failloux_1994_J.Med.Entomol_31_639
PubMedID: 7966164

Title : Action of Esterase B1 on Chlorpyrifos in Organophosphate-Resistant Culex Mosquitos - Cuany_1993_Pestic.Biochem.Physiol_45_1
Author(s) : Cuany A , Handani J , Berge J , Fournier D , Raymond M , Georghiou GP , Pasteur N
Ref : Pesticide Biochemistry and Physiology , 45 :1 , 1993
Abstract : Esterase B1 activity in Culex pipiens mosquitoes was strongly inhibited by oxidized organophosphates (OP), but not by nonoxidized forms or by carbamates. Inhibition by chlorpyrifos oxon and paraoxon remained total during the 2 hr following the removal of free insecticide molecules, indicating that hydrolysis by esterase B1 is either very slow or absent. This hypothesis was confirmed by comparing the fate of [14C]chlorpyrifos in larvae of strains TEM-R (with the over-produced esterase B1) and MSE (lacking an overproduced esterase). As expected, large quantities of chlorpyrifos oxon were observed in the two strains, but no other metabolite was found in TEM-R. It is concluded that esterase B1 confers resistance at least to diethyl OPs through sequestering rather than metabolism, as is also the case with the overproduced esterase E4 of Myzus persicae.
ESTHER : Cuany_1993_Pestic.Biochem.Physiol_45_1
PubMedSearch : Cuany_1993_Pestic.Biochem.Physiol_45_1

Title : Resistance to temephos, an organophosphorous insecticide, in Culex pipiens from Tunisia, North Africa - Ben_1993_J.Am.Mosq.Control.Assoc_9_335
Author(s) : Ben Cheikh H , Pasteur N
Ref : J Am Mosq Control Assoc , 9 :335 , 1993
Abstract : Resistance to temephos, an organophosphorous insecticide (OP), was found to be low (2-fold) in 2 Culex pipiens populations collected in Sayada (mid-eastern Tunisia). This resistance was synergized by an esterase inhibitor (DEF). Two sets of over-produced esterases (A2-B2 and A4-B4), known to be involved in resistance, were identified in almost 50% of the examined insects. In addition, 3% of insects had an insensitive acetylcholinesterase. After selecting larvae of one of the samples (ES) with temephos for 6 generations, a 9-fold increase in resistance was observed, and all mosquitoes were found to carry esterases A2-B2 and an insensitive acetylcholinesterase. These results must be considered in future mosquito control programs, since 2 of the identified genes can lead to high resistance to several organophosphorous insecticides.
ESTHER : Ben_1993_J.Am.Mosq.Control.Assoc_9_335
PubMedSearch : Ben_1993_J.Am.Mosq.Control.Assoc_9_335
PubMedID: 7504077

Title : Evolution of resistance genes in absence of insecticide selection in a hypogeous population of Culex pipiens from the French Alps - Rivet_1993_J.Am.Mosquito.Control.Assoc_9_206
Author(s) : Rivet Y , Pasteur N
Ref : Journal of the American Mosquito Control Association , 9 :206 , 1993
Abstract : A monthly survey of resistance gene frequencies was conducted in a larval population of Culex pipiens breeding in an hypogeous site ("molestus" form) between July 1989 and September 1991, after interrupting mosquito control. Several significant variations in resistance gene frequency were observed. Some variations are explained by fitness differences between resistant and susceptible insects, others by an immigration of insects from the surrounding epigeous populations ("pipiens" form), which are highly resistant.
ESTHER : Rivet_1993_J.Am.Mosquito.Control.Assoc_9_206
PubMedSearch : Rivet_1993_J.Am.Mosquito.Control.Assoc_9_206
PubMedID: 7688796

Title : Worldwide migration of amplified insecticide resistance genes in mosquitoes. - Raymond_1991_Nature_350_151
Author(s) : Raymond M , Callaghan A , Fort P , Pasteur N
Ref : Nature , 350 :151 , 1991
Abstract : In Culex pipiens, overproduction of nonspecific esterases is a common mechanism of resistance to organophosphate insecticides. The esterases are attributed to closely linked loci named A and B according to substrate preference, and overproduction of all esterases B is due to gene amplification. Distribution of electrophoretically distinct variants of overproduced esterases A and B is geographically restricted, with the exception of esterases A2 and B2, always found together throughout at least three continents. To determine whether this situation is due to migration or to a high mutation rate, esterase B structural genes and their flanking regions were compared by sequence and/or restriction fragment length polymorphism analysis. Whereas structural genes were similar, flanking regions of electrophoretically dissimilar esterases B varied considerably. In contrast, flanking sequences of esterases B2 from different geographical locations (Africa, Asia, North America) were identical. These results suggest that amplified esterase B2 genes originated from an initial event that has subsequently spread organophosphate insecticide resistance by migration.
ESTHER : Raymond_1991_Nature_350_151
PubMedSearch : Raymond_1991_Nature_350_151
PubMedID: 2005964

Title : Esterases A2 and B2 in Culex quinquefasciatus (Diptera: Culicidae): role in organophosphate resistance and linkage - Wirth_1990_J.Med.Entomol_27_202
Author(s) : Wirth MC , Marquine M , Georghiou GP , Pasteur N
Ref : Journal of Medical Entomology , 27 :202 , 1990
Abstract : Two highly active esterases, A2 and B2, were isolated in SeLax, a strain of Culex quinquefasciatus Say from California which demonstrated resistance levels of 19, 14, and 4.3 times to the organophosphate insecticides chlorpyrifos, temephos, and malathion, respectively. Selection of SeLax by temephos during 31 generations increased resistance to this insecticide to 65 times. This resistance was shown to be DEF-suppressible, monofactorial, and strongly associated with the presence of esterases A2 and B2. Although these two esterases are encoded by distinct structural genes, no disjunction was observed when SeLax was crossed to S-Lab, a susceptible strain, or to S54, a strain resistant to organophosphates by means of esterase A1. However, when SeLax was crossed to strain Tem-R, which is resistant to organophosphates because of a highly active esterase B1, all possible recombinants occurred. These results were discussed in relation to the recent discovery that increased activity of B esterases in the genus Culex is caused by gene amplification.
ESTHER : Wirth_1990_J.Med.Entomol_27_202
PubMedSearch : Wirth_1990_J.Med.Entomol_27_202
PubMedID: 2093766

Title : Amplification of various esterase B's responsible for organophosphate resistance in Culex mosquitoes -
Author(s) : Raymond M , Beyssat-Arnaouty V , Sivasubramanian N , Mouches C , Georghiou GP , Pasteur N
Ref : Biochemical Genetics , 27 :417 , 1989
PubMedID: 2559713

Title : Genetic association between highly active esterases and organophosphate resistance in Culex tarsalis - Prabhaker_1987_J.Am.Mosq.Control.Assoc_3_473
Author(s) : Prabhaker N , Georghiou GP , Pasteur N
Ref : J Am Mosq Control Assoc , 3 :473 , 1987
Abstract : The genetics of two highly active esterases, A3H and B3H, in a methyl parathion-resistant strain (MP-R) of Culex tarsalis was investigated in relation to organophosphate (OP) resistance. The increased activity of esterase A3 and of esterase B3 is under the control of two distinct and closely linked (approximately 4.4 centimorgans) genes. Each gene possesses two forms, one controlling high activity (A3H or B3H, respectively) and one controlling low activity (A3L or B3L, respectively) of the enzymes. Organophosphate resistance in the MP-R strain is strongly associated with the presence of these highly active esterases. The results are discussed in relation to the present knowledge on the mechanisms responsible for high activity of esterases observed in other OP-resistant mosquitoes of the genus Culex.
ESTHER : Prabhaker_1987_J.Am.Mosq.Control.Assoc_3_473
PubMedSearch : Prabhaker_1987_J.Am.Mosq.Control.Assoc_3_473
PubMedID: 3504931

Title : Identification of resistance mechanisms in Culex pipiens (Diptera: Culicidae) from southern France: insensitive acetylcholinesterase and detoxifying oxidases -
Author(s) : Raymond M , Fournier D , Bride JM , Cuany A , Berge JB , Magnin M , Pasteur N
Ref : J Econ Entomol , 79 :1452 , 1986
PubMedID: 3805481

Title : Amplification of an esterase gene is responsible for insecticide resistance in a California Culex mosquito - Mouches_1986_Science_233_778
Author(s) : Mouches C , Pasteur N , Berge JB , Hyrien O , Raymond M , de Saint Vincent BR , de Silvestri M , Georghiou GP
Ref : Science , 233 :778 , 1986
Abstract : An esterase gene from the mosquito Culex quinquefasciatus that is responsible for resistance to a variety of organophosphorus (OP) insecticides was cloned in lambda gt11 phage. This gene was used to investigate the genetic mechanism of the high production of the esterase B1 it encodes in OP-resistant Culex quinquefasciatus Say (Tem-R strain) from California. Adults of the Tem-R strain were found to possess at least 250 times more copies of the gene than adults of a susceptible strain (S-Lab). The finding that selection by pesticides may result in the amplification of genes encoding detoxifying enzymes in whole, normally developed, reproducing insects emphasizes the biological importance of this mechanism and opens new areas of investigation in pesticide resistance management.
ESTHER : Mouches_1986_Science_233_778
PubMedSearch : Mouches_1986_Science_233_778
PubMedID: 755546

Title : Single-mosquito test to determine genotypes with an acetylcholinesterase insensitive to inhibition to propoxur insecticide - Raymond_1985_J.Am.Mosquito.Control.Assoc_1_425
Author(s) : Raymond M , Fournier D , Berge JB , Cuany A , Bride JM , Pasteur N
Ref : Journal of the American Mosquito Control Association , 1 :425 , 1985
Abstract : A sensitive technique allowing to identify the three genotypes (AceSS, AceRR and AceRS) of the Ace gene existing in natural populations of Culex pipiens in southern France is described. The technique is based on the comparison of AChE (acetylcholinesterase) activity in 3 equal aliquots taken from the homogenate of a single mosquito (a) in absence of inhibitor (RA), (b) in presence of eserine that inhibits the AChE encoded by AceS and AceR alleles (RI) and (c) in presence of a concentration of propoxur inhibiting the AChE coded by the AceS allele but not by the AceR allele (RG). The mosquito tested is AceSS when RG = RI, AceRR when RG = RA and AceRS when RI less than RG less than RA.
ESTHER : Raymond_1985_J.Am.Mosquito.Control.Assoc_1_425
PubMedSearch : Raymond_1985_J.Am.Mosquito.Control.Assoc_1_425
PubMedID: 3880259