Vontas J

References (45)

Title : Monitoring Aedes populations for arboviruses, Wolbachia, insecticide resistance and its mechanisms in various agroecosystems in Benin - Ateutchia-Ngouanet_2024_Acta.Trop__107178
Author(s) : Ateutchia-Ngouanet S , Nanfack-Minkeu F , Mavridis K , Wanji S , Demanou M , Vontas J , Djouaka R
Ref : Acta Trop , :107178 , 2024
Abstract : Aedes mosquitoes are the main vectors of arboviruses in Benin. Cases of dengue have been reported in Benin with all four serotypes of the virus actively circulating in this region. Some agricultural settings are known to harbor Aedes vectors responsible for the transmission of arboviruses. The massive use of certain insecticides in agricultural settings has probably contributed to insecticide resistance in these vectors. In Benin, the susceptibility of arbovirus vectors to insecticides is poorly studied. In addition, the distribution of Wolbachia spp., which is used against some arboviruses is unknown. Moreover, there is limited information regarding the vectors responsible for the transmission of arboviruses in Benin. This present study monitored the species composition, arboviruses, and Wolbachia symbiont status, as well as the phenotypic and molecular insecticide resistance profile of Aedes populations from three agroecosystems in Benin. Aedes species identification was performed morphologically and confirmed using qPCR. (RT)-qPCR assay was applied for monitoring the presence of DENV, CHIKV, ZIKV, and WNV pathogens as well as for naturally occurring Wolbachia symbionts. Insecticide resistance was assessed phenotypically, by permethrin (0.75%) exposure of Adults (F0) using World Health Organization (WHO) bioassay protocols, and at the molecular level, using TaqMan (RT)-qPCR assays for assessing knock-down resistance (kdr) mutations (F1534C, V1016G/I, and S989P) and the expression levels of eight detoxification genes (P450s from the CYP9 and CYP6 families, carboxylesterases and glutathione-S-transferases). Aedes aegypti (Ae. aegypti) mosquitoes were the most abundant (93.9%) in the three agroecosystems studied, followed by Aedes albopictus (Ae. albopictus) mosquitoes (6.1%). No arboviruses were detected in the study's mosquito populations. Naturally occurring Wolbachia symbionts were present in 7 pools out of 15 pools tested. This could influence the effectiveness of vector control strategies based on exogenously introduced Wolbachia, all present in the three agroecosystems. Full susceptibility to permethrin was observed in all tested populations of Ae. albopictus. On the contrary, Ae. aegypti were found to be resistant in all three agroecosystem sites except for banana plantation sites, where full susceptibility was observed. Molecular analysis revealed that individual target site resistance kdr mutations F1534C and V1016G/I were detected in most Ae. aegypti populations. Additionally, double mutant (F1534C + V1016G/I) mosquitoes were found in some populations, and in one case, triple mutant (F1534C + V1016G/I + S989P) mosquitoes were detected. Metabolic resistance, as reflected by overexpression of three P450 genes (CYP6BB2, CYP9J26, and CYP9J32), was also detected in Ae. aegypti mosquitoes. Our study provides information that could be used to strategize future vector control strategies and highlights the importance of continuing vector surveillance. Future studies should assess the effect of piperonyl butoxide (PBO) on metabolic resistance and identify the different strains of Wolbachia spp., to choose the best vector control strategies in Benin.
ESTHER : Ateutchia-Ngouanet_2024_Acta.Trop__107178
PubMedSearch : Ateutchia-Ngouanet_2024_Acta.Trop__107178
PubMedID: 38461924

Title : Molecular monitoring of insecticide resistance in major disease vectors in Armenia - Paronyan_2024_Parasit.Vectors_17_54
Author(s) : Paronyan L , Babayan L , Vardanyan H , Manucharyan A , Papapostolou KM , Balaska S , Vontas J , Mavridis K
Ref : Parasit Vectors , 17 :54 , 2024
Abstract : BACKGROUND: Armenia is considered particularly vulnerable to life-threatening vector-borne diseases (VBDs) including malaria, West Nile virus disease and leishmaniasis. However, information relevant for the control of the vectors of these diseases, such as their insecticide resistance profile, is scarce. The present study was conducted to provide the first evidence on insecticide resistance mechanisms circulating in major mosquito and sand fly populations in Armenia. METHODS: Sampling sites were targeted based mainly on previous historical records of VBD occurrences in humans and vertebrate hosts. Initially, molecular species identification on the collected vector samples was performed. Subsequently, molecular diagnostic assays [polymerase chain reaction (PCR), Sanger sequencing, PCR-restriction fragment length polymorphism (RFLP), quantitative PCR (qPCR)] were performed to profile for major insecticide resistance mechanisms, i.e. target site insensitivity in voltage-gated sodium channel (vgsc) associated with pyrethroid resistance, acetylcholinesterase (ace-1) target site mutations linked to organophosphate (OP) and carbamate (CRB) resistance, chitin synthase (chs-1) target site mutations associated with diflubenzuron (DFB) resistance and gene amplification of carboxylesterases (CCEs) associated with resistance to the OP temephos. RESULTS: Anopheles mosquitoes were principally represented by Anopheles sacharovi, a well-known malaria vector in Armenia, which showed no signs of resistance mechanisms. Contrarily, the knockdown resistance (kdr) mutations V1016G and L1014F/C in the vgsc gene were detected in the arboviral mosquito vectors Aedes albopictus and Culex pipiens, respectively. The kdr mutation L1014S was also detected in the sand fly, vectors of leishmaniasis, Phlebotomus papatasi and P. tobbi, whereas no mutations were found in the remaining collected sand fly species, P. sergenti, P. perfiliewi and P. caucasicus. CONCLUSIONS: This is the first study to report on molecular mechanisms of insecticide resistance circulating in major mosquito and sand fly disease vectors in Armenia and highlights the need for the establishment of systematic resistance monitoring practices for the implementation of evidence-based control applications.
ESTHER : Paronyan_2024_Parasit.Vectors_17_54
PubMedSearch : Paronyan_2024_Parasit.Vectors_17_54
PubMedID: 38321481

Title : Analysis of insecticide resistance and de novo transcriptome assembly of resistance associated genes in the European grapevine moth, Lobesia botrana (Lepidoptera: Tortricidae) - Albaz_2024_Bull.Entomol.Res__1
Author(s) : Albaz E , Katsavou E , Cagatay NS , Ioannidis P , Ilias A , Mylona K , Kremi K , Roditakis E , Guz N , Vontas J
Ref : Bull Entomol Res , :1 , 2024
Abstract : The European grapevine moth Lobesia botrana (Denis & Shiffermller 1776) is an economically important pest of the vine-growing areas worldwide. Chemical insecticides have been used for its control; however, its resistance status is largely unknown in many regions. We monitored the susceptibility of several L. botrana populations from Greece and Turkey. In addition, based on RNAseq transcriptome analysis, we identified and phylogenetically classify the cytochrome P450 genes of L. botrana, as well as analysed target site sequences and looked for the presence of known resistance mutations. Resistance against chlorantraniliprole, alpha-cypermethrin, spinetoram, etofenprox, and acetamiprid was very low (below 2.5-fold in all cases, compared to a reference strain from Greece) in all populations from Greece that were included in the study. However, resistance against indoxacarb (4-30-fold), spinosad (5-59-fold), and deltamethrin (18-30 fold) was detected in the L. botrana populations from Turkey, compared to a reference population from Turkey. De novo transcriptome assembly and manual annotation, and subsequent PCR-based analysis of insecticide target sequences (i.e. voltage-gated sodium channel - VGSC: target of pyrethroids and oxadiazines; nicotinic acetylcholine receptor subunit a6 - nAChR_alpha6: target of spinosad; ryanodine receptor - RyR: target of diamides; glutamate-gated chloride channel - GluCl: target of avermectins and; acetylcholinesterase - AChE: target of organophosphates) showed the absence of known resistance mutations in all specimens from both countries. Finally, the L. botrana CYPome (116 genes) was manually analysed and phylogenetically characterised, to provide resources for future studies that will aim the analysis of metabolic resistance.
ESTHER : Albaz_2024_Bull.Entomol.Res__1
PubMedSearch : Albaz_2024_Bull.Entomol.Res__1
PubMedID: 38327090

Title : Species composition, infection rate and detection of resistant alleles in Anopheles funestus (Diptera: Culicidae) from Lare, a malaria hotspot district of Ethiopia - Woyessa_2023_Malar.J_22_233
Author(s) : Woyessa D , Morou E , Wipf N , Dada N , Mavridis K , Vontas J , Yewhalaw D
Ref : Malar J , 22 :233 , 2023
Abstract : BACKGROUND: Anopheles funestus, which is considered as secondary vector of malaria in Ethiopia, is known to have several morphologically indistinguishable (sibling) species. Accurate identification of sibling species is crucial to understand their biology, behaviour and vector competence. In this study, molecular identification was conducted on the Ethiopian An. funestus populations. Moreover, insecticide resistance mechanism markers were detected, including ace N485I, kdr L1014F, L1014S, and CYP6P9a TaqMan qPCR was used to detect the infective stage of the parasite from field collected adult female An. funestus populations. METHODS: Adult female mosquito collection was conducted from Lare, Gambella Regional State of Ethiopia between June 2018 to July 2020 using CDC light traps and HLC. Sub-samples of the morphologically identified An. funestus mosquitoes were molecularly identified using species-specific PCR, and the possible presence of insecticide resistance alleles was investigated using TaqMan qPCR (N485I-Ace-1), PCR-Sanger sequencing (L1014F-kdr), and PCR-RFLP (CYP6P9a resistance allele). Following head/thorax dissection, the TaqMan qPCR assay was used to investigate the presence of the infective stage Plasmodium parasite species. RESULTS: A total of 1086 adult female An. funestus mosquitoes were collected during the study period. All sub-samples (N = 20) that were morphologically identified as An. funestus sensu lato (s.l.) were identified as An. funestus sensu stricto (s.s.) using species- specific PCR assay. The PCR-RFLP assay that detects the CYP6P9a resistance allele that confers pyrethroid resistance in An. funestus was applied in N = 30 randomly selected An. funestus s.l. SPECIMENS: None of the specimens showed a digestion pattern consistent with the presence of the CYP6P9a resistance allele in contrast to what was observed in the positive control. Consequently, all samples were characterized as wild type. The qPCR TaqMan assay that detects the N485I acetylcholinesterase-1 mutation conferring resistance to organophosphates/carbamates in An. funestus was used in (N = 144) samples. All samples were characterized as wild type. The kdr L1014F and L1014S mutations in the VGSC gene that confer resistance to pyrethroids and DDT were analysed with direct Sanger sequencing after PCR and clean-up of the PCR products were also characterized as wild type. None of the samples (N = 169) were found positive for Plasmodium (P. falciparum/ovale/malariae/vivax) detection. CONCLUSION: All An. funestus s.l. samples from Lare were molecularly identified as An. funestus s.s. No CYP6P9, N485I acetylcholinesterase 1, kdr L1014F or L1014S mutations were detected in the An. funestus samples. None of the An. funestus samples were positive for Plasmodium. Although the current study did not detect any insecticide resistant mechanism, it provides a reference for future vector monitoring programmes. Regular monitoring of resistance mechanisms covering wider geographical areas of Ethiopia where this vector is distributed is important for improving the efficacy of vector control programs.
ESTHER : Woyessa_2023_Malar.J_22_233
PubMedSearch : Woyessa_2023_Malar.J_22_233
PubMedID: 37573300

Title : Multiple TaqMan qPCR and droplet digital PCR (ddPCR) diagnostics for pesticide resistance monitoring and management, in the major agricultural pest Tetranychus urticae - Mavridis_2022_Pest.Manag.Sci_78_263
Author(s) : Mavridis K , Papapostolou KM , Riga M , Ilias A , Michaelidou K , Bass C , Van Leeuwen T , Tsagkarakou A , Vontas J
Ref : Pest Manag Sci , 78 :263 , 2022
Abstract : BACKGROUND: Decisions on which pesticide to use in agriculture are expected to become more difficult, as the number of available chemicals is decreasing. For Tetranychus urticae (T. urticae), a major pest for which a number of candidate markers for pesticide resistance are in place, molecular diagnostics could support decision-making for the rational use of acaricides. RESULTS: A suite of 12 TaqMan qPCR assays [G314D (GluCl1), G326E, I321T (GluCl3), G119S, F331W (Ace-1), H92R (PSST), L1024V, F1538I (VGSC), I1017F (CHS1), G126S, S141F, P262T (cytb)], were validated against Sanger-sequencing, and subsequently adapted for use with the ddPCR technology. The concordance correlation coefficient between the actual and ddPCR measured mutant allelic frequencies was 0.995 (95% CI = 0.991-0.998), and no systematic, proportional, or random differences were detected. The achieved Limit of Detection (LoD) was 0.1% (detection of one mutant in a background of 999 wild type mites). The ddPCR assay panel was then assessed in terms of agreement with phenotypic resistance, through a pilot application in field populations from Crete, with strong correlation and thus predictive and diagnostic value of the molecular assays in some cases (e.g., etoxazole and abamectin resistance). Molecular diagnostics were able to capture incipient resistance that was otherwise missed by phenotypic bioassays. The molecular and phenotypic resistance screening of T. urticae field populations from Crete, revealed both multi-resistant and susceptible populations. CONCLUSION: The highly sensitive T. urticae molecular diagnostic platforms developed in this study could prove a valuable tool for pesticide resistance management.
ESTHER : Mavridis_2022_Pest.Manag.Sci_78_263
PubMedSearch : Mavridis_2022_Pest.Manag.Sci_78_263
PubMedID: 34480408

Title : Bendiocarb and Malathion Resistance in Two Major Malaria Vector Populations in Cameroon Is Associated with High Frequency of the G119S Mutation (Ace-1) and Overexpression of Detoxification Genes - Ngangue-Siewe_2022_Pathogens_11_
Author(s) : Ngangue-Siewe IN , Ndjeunia-Mbiakop P , Kala-Chouakeu NA , Bamou R , Talipouo A , Djamouko-Djonkam L , Vontas J , Mavridis K , Tombi J , Tchuinkam T , Mbida-Mbida JA , Antonio-Nkondjio C
Ref : Pathogens , 11 : , 2022
Abstract : The spread of pyrethroid resistance in malaria vectors is a major threat affecting the performance of current control measures. However, there is still not enough information on the resistance profile of mosquitoes to carbamates and organophosphates which could be used as alternatives. The present study assessed the resistance profile of Anopheles gambiae s.l. to bendiocarb and malathion, at the phenotypic and molecular levels, in different eco-epidemiological settings in Cameroon. Anopheles gambiae s.l. mosquitoes were collected from four eco-epidemiological settings across the country and their susceptibility level to bendiocarb and malathion was determined using WHO tubes bioassays. The ace-1 target site G119S mutation was screened by PCR. Reverse Transcription quantitative PCR 3-plex TaqMan assays were used to quantify the level of expression of eight genes associated with metabolic resistance. Resistance to malathion and/or bendiocarb was recorded in all study sites except in mosquitoes collected in Kaele and Njombe. The Ace-1 (G119S) mutation was detected in high frequencies (>40%) in Kekem and Santchou. Both An. gambiae and An. coluzzii were detected carrying this mutation. The cytochrome P450s gene Cyp6p3 associated with carbamate resistance and the glutathione S-transferase gene Gste2 associated with organophosphate resistance were found to be overexpressed. Genes associated with pyrethroid (Cyp6m2, Cyp9k1, Cyp6p3) and organochlorine (Gste2, Cyp6z1, Cyp6m2) and cuticle resistance (Cyp4g16) were also overexpressed. The rapid spread of resistance to organophosphates and carbamates could seriously compromise future control strategies based on IRS. It is therefore becoming important to assess the magnitude of bendiocarb and malathion resistance countrywide.
ESTHER : Ngangue-Siewe_2022_Pathogens_11_
PubMedSearch : Ngangue-Siewe_2022_Pathogens_11_
PubMedID: 35894047

Title : Next-generation molecular diagnostics (TaqMan qPCR and ddPCR) for monitoring insecticide resistance in Bemisia tabaci - Mavridis_2022_Pest.Manag.Sci__
Author(s) : Mavridis K , Papapostolou KM , Ilias A , Michaelidou K , Stavrakaki M , Roditakis E , Tsagkarakou A , Bass C , Vontas J
Ref : Pest Manag Sci , : , 2022
Abstract : BACKGROUND: Insecticide resistance has developed in several populations of the whitefly Bemisia tabaci worldwide and threatens to compromise the efficacy of chemical control. The molecular mechanisms underpinning resistance have been characterized and markers associated with the trait have been identified, allowing the development of diagnostics for individual insects. RESULTS: TaqMan and Droplet Digital PCR (ddPCR) assays were developed and validated, in individual and pooled whitefly samples, respectively, for the following target-site mutations: the acetylcholinesterase (ace1) F331W mutation conferring organophosphate-resistance; the voltage-gated sodium channel (vgsc) mutations L925I and T929V conferring pyrethroid-resistance; and the acetyl-CoA carboxylase (acc) A2083V mutation conferring ketoenol-resistance. The ddPCR's limit of detection (LoD) was <0.2% (i.e. detection of one heterozygote whitefly in a pool of 249 wild-type individuals). The assays were applied in 11 B. tabaci field populations from four locations in Crete, Greece. The F331W mutation was detected to be fixed or close to fixation in eight of 11 B. tabaci populations, and at lower frequency in the remaining ones. The pyrethroid-resistance mutations were detected at very high frequencies. The A2083V spiromesifen resistance mutation was detected in eight of 11 populations (frequencies = 6.16-89.56%). Spiromesifen phenotypic resistance monitoring showed that the populations tested had variable levels of resistance, ranging from full susceptibility to high resistance. A strong spiromesifen-resistance phenotype-genotype (A2083V) correlation (r(s) = -0.839, P = 0.002) was observed confirming the ddPCR diagnostic value. CONCLUSION: The ddPCR diagnostics developed in this study are a valuable tool to support evidence-based rational use of insecticides and resistance management strategies. 2022 Society of Chemical Industry.
ESTHER : Mavridis_2022_Pest.Manag.Sci__
PubMedSearch : Mavridis_2022_Pest.Manag.Sci__
PubMedID: 36054028

Title : Multi-insecticide resistant malaria vectors in the field remain susceptible to malathion, despite the presence of Ace1 point mutations - Wipf_2022_PLoS.Genet_18_e1009963
Author(s) : Wipf NC , Duchemin W , Kouadio FA , Fodjo BK , Sadia CG , Mouhamadou CS , Vavassori L , Maser P , Mavridis K , Vontas J , Muller P
Ref : PLoS Genet , 18 :e1009963 , 2022
Abstract : Insecticide resistance in Anopheles mosquitoes is seriously threatening the success of insecticide-based malaria vector control. Surveillance of insecticide resistance in mosquito populations and identifying the underlying mechanisms enables optimisation of vector control strategies. Here, we investigated the molecular mechanisms of insecticide resistance in three Anopheles coluzzii field populations from southern Cote d'Ivoire, including Agboville, Dabou and Tiassale. All three populations were resistant to bendiocarb, deltamethrin and DDT, but not or only very weakly resistant to malathion. The absence of malathion resistance is an unexpected result because we found the acetylcholinesterase mutation Ace1-G280S at high frequencies, which would typically confer cross-resistance to carbamates and organophosphates, including malathion. Notably, Tiassale was the most susceptible population to malathion while being the most resistant one to the pyrethroid deltamethrin. The resistance ratio to deltamethrin between Tiassale and the laboratory reference colony was 1,800 fold. By sequencing the transcriptome of individual mosquitoes, we found numerous cytochrome P450-dependent monooxygenases - including CYP6M2, CYP6P2, CYP6P3, CYP6P4 and CYP6P5 - overexpressed in all three field populations. This could be an indication for negative cross-resistance caused by overexpression of pyrethroid-detoxifying cytochrome P450s that may activate pro-insecticides, thereby increasing malathion susceptibility. In addition to the P450s, we found several overexpressed carboxylesterases, glutathione S-transferases and other candidates putatively involved in insecticide resistance.
ESTHER : Wipf_2022_PLoS.Genet_18_e1009963
PubMedSearch : Wipf_2022_PLoS.Genet_18_e1009963
PubMedID: 35143477

Title : High insecticide resistance mediated by different mechanisms in Culex quinquefasciatus populations from the city of Yaound, Cameroon - Talipouo_2021_Sci.Rep_11_7322
Author(s) : Talipouo A , Mavridis K , Nchoutpouen E , Djiappi-Tchamen B , Fotakis EA , Kopya E , Bamou R , Kekeunou S , Awono-Ambene P , Balabanidou V , Balaska S , Wondji CS , Vontas J , Antonio-Nkondjio C
Ref : Sci Rep , 11 :7322 , 2021
Abstract : Culex mosquitoes particularly Culex quinquefasciatus are important arboviral and filariasis vectors, however despite this important epidemiological role, there is still a paucity of data on their bionomics. The present study was undertaken to assess the insecticide resistance status of Cx. quinquefasciatus populations from four districts of Yaounde (Cameroon). All Culex quinquefasciatus populations except one displayed high resistance to bendiocarb and malathion with mortalities ranging from 0 to 89% while high resistance intensity against both permethrin and deltamethrin was recorded. Molecular analyses revealed high frequencies of the ACE-1 G119S mutation (ranging from 0 to 33%) and kdr L1014F allele (ranging from 55 to 74%) in all Cx. quinquefasciatus populations. Significant overexpression was detected for cytochrome P450s genes CYP6AA7 and CYP6Z10, as well as for Esterase A and Esterase B genes. The total cuticular hydrocarbon content, a proxy of cuticular resistance, was significantly increased (compared to the S-lab strain) in one population. The study confirms strong insecticide resistance mediated by different mechanisms in Cx. quinquefasciatus populations from the city of Yaounde. The expansion of insecticide resistance in Culex populations could affect the effectiveness of current vector control measures and stress the need for the implementation of integrated vector control strategies in urban settings.
ESTHER : Talipouo_2021_Sci.Rep_11_7322
PubMedSearch : Talipouo_2021_Sci.Rep_11_7322
PubMedID: 33795804

Title : Population structure and insecticide resistance status of Tuta absoluta populations from Turkey - Inak_2021_Pest.Manag.Sci__
Author(s) : Inak E , Ozdemir E , Atis AE , Randa Zelyut F , Inak A , Demir U , Roditakis E , Vontas J
Ref : Pest Manag Sci , : , 2021
Abstract : BACKGROUND: Tuta absoluta is a devastating pest in tomato production areas worldwide. After its first introduction to Turkey in 2009, it quickly became the major pest of tomato growing areas. Although some biocontrol agents have been used especially in greenhouses, the main control of T. absoluta relies heavily on chemical insecticides. However, failure in chemical control has often been reported due to resistance development. In this study, we investigated: 1) the population structure of 22 T. absoluta populations across Turkey, by analysing haplotypes, based on the cytochrome oxidase subunit I gene; 2) the efficacy of three registered insecticides from different classes (metaflumizone, chlorantraniliprole and spinosad) in real field - greenhouse conditions; 3) the geographic distribution of target-site mutations associated with insecticide resistance. RESULTS: The efficacy of spinosad was higher than chlorantraniliprole and metaflumizone in the greenhouse trials, as documented by the mortality rates obtained, up to 14 days post application. Known resistance mutations in ryanodine receptors (RyR) (i.e. the I4790M/K and G4946E), nicotinic acetylcholine receptors (G275E), acetylcholinesterases (A201S) and voltage-gated sodium channels (F1845Y and V1848I) were found at various frequencies, across the populations genotyped. The I4790K diamide resistance mutation in the RyR has been reported for the first time in T. absoluta populations. Although a total of 8 haplotypes were found, the overall mean genetic distance was lower than 0.001 indicating the high genetic homogeneity among Turkish T. absoluta populations. CONCLUSION: The results will contribute to design area-wide resistance management programs in T. absoluta control in Turkey. However, more monitoring studies are needed to implement evidence-based IRM strategies in the frame of integrated pest management (IPM). This article is protected by copyright. All rights reserved.
ESTHER : Inak_2021_Pest.Manag.Sci__
PubMedSearch : Inak_2021_Pest.Manag.Sci__
PubMedID: 34151488
Gene_locus related to this paper: tutab-ACHE1

Title : Global patterns in genomic diversity underpinning the evolution of insecticide resistance in the aphid crop pest Myzus persicae - Singh_2021_Commun.Biol_4_847
Author(s) : Singh KS , Cordeiro EMG , Troczka BJ , Pym A , Mackisack J , Mathers TC , Duarte A , Legeai F , Robin S , Bielza P , Burrack HJ , Charaabi K , Denholm I , Figueroa CC , ffrench-Constant RH , Jander G , Margaritopoulos JT , Mazzoni E , Nauen R , Ramirez CC , Ren G , Stepanyan I , Umina PA , Voronova NV , Vontas J , Williamson MS , Wilson ACC , Xi-Wu G , Youn YN , Zimmer CT , Simon JC , Hayward A , Bass C
Ref : Commun Biol , 4 :847 , 2021
Abstract : The aphid Myzus persicae is a destructive agricultural pest that displays an exceptional ability to develop resistance to both natural and synthetic insecticides. To investigate the evolution of resistance in this species we generated a chromosome-scale genome assembly and living panel of >110 fully sequenced globally sampled clonal lines. Our analyses reveal a remarkable diversity of resistance mutations segregating in global populations of M. persicae. We show that the emergence and spread of these mechanisms is influenced by host-plant associations, uncovering the widespread co-option of a host-plant adaptation that also offers resistance against synthetic insecticides. We identify both the repeated evolution of independent resistance mutations at the same locus, and multiple instances of the evolution of novel resistance mechanisms against key insecticides. Our findings provide fundamental insights into the genomic responses of global insect populations to strong selective forces, and hold practical relevance for the control of pests and parasites.
ESTHER : Singh_2021_Commun.Biol_4_847
PubMedSearch : Singh_2021_Commun.Biol_4_847
PubMedID: 34234279

Title : Pyrethroid and Etofenprox Resistance in Anopheles gambiae and Anopheles coluzzii from Vegetable Farms in Yaound, Cameroon: Dynamics, Intensity and Molecular Basis - Piameu_2021_Molecules_26_
Author(s) : Piameu M , Nwane P , Toussile W , Mavridis K , Wipf NC , Kouadio PF , Mbakop LR , Mandeng S , Ekoko WE , Toto JC , Ngaffo KL , Ngo Etounde PK , Ngantchou AT , Chouaibou M , Muller P , Awono-Ambene P , Vontas J , Etang J
Ref : Molecules , 26 : , 2021
Abstract : Previous studies have indicated widespread insecticide resistance in malaria vector populations from Cameroon. However, the intensity of this resistance and underlying mechanisms are poorly known. Therefore, we conducted three cross-sectional resistance surveys between April 2018 and October 2019, using the revised World Health Organization protocol, which includes resistance incidences and intensity assessments. Field-collected Anopheles gambiae s.l. populations from Nkolondom, Nkolbisson and Ekie vegetable farms in the city of Yaounde were tested with deltamethrin, permethrin, alpha-cypermethrin and etofenprox, using 1x insecticide diagnostic concentrations for resistance incidence, then 5x and 10x concentrations for resistance intensity. Subsamples were analyzed for species identification and the detection of resistance-associated molecular markers using TaqMan(a) qPCR assays. In Nkolbisson, both An. coluzzii (96%) and An. gambiae s.s. (4%) were found together, whereas only An. gambiae s.s. was present in Nkolondom, and only An. coluzzii was present in Ekie. All three populations were resistant to the four insecticides (<75% mortality rates-MR1x), with intensity generally fluctuating over the time between mod-erate (<98%-MR5x; <=98%-MR10x) and high (76-97%-MR10x). The kdr L995F, L995S, and N1570Y, and the Ace-1 G280S-resistant alleles were found in An. gambiae from Nkolondom, at 73%, 1%, 16% and 13% frequencies, respectively, whereas only the kdr L995F was found in An. gambiae s.s. from Nkolbisson at a 50% frequency. In An. coluzzii from Nkolbisson and Ekie, we detected only the kdr L995F allele at 65% and 60% frequencies, respectively. Furthermore, expression levels of Cyp6m2, Cyp9k1, and Gste2 metabolic genes were highly upregulated (over fivefold) in Nkolondom and Nkolbisson. Pyrethroid and etofenprox-based vector control interventions may be jeopardized in the prospected areas, due to high resistance intensity, with multiple mechanisms in An. gambiae s.s. and An. coluzzii.
ESTHER : Piameu_2021_Molecules_26_
PubMedSearch : Piameu_2021_Molecules_26_
PubMedID: 34577014

Title : Identification and characterization of striking multiple-insecticide resistance in a Tetranychus urticae field population from Greece - Papapostolou_2021_Pest.Manag.Sci_77_666
Author(s) : Papapostolou KM , Riga M , Charamis J , Skoufa E , Souchlas V , Ilias A , Dermauw W , Ioannidis P , Van Leeuwen T , Vontas J
Ref : Pest Manag Sci , 77 :666 , 2021
Abstract : BACKGROUND: Tetranychus urticae is a notorious crop pest with world-wide distribution that has developed resistance to a wide range of acaricides. Here, we investigated the resistance levels of a T. urticae population collected from an ornamental greenhouse in Peloponnese, Greece, and analyzed its resistance mechanisms at the molecular level. RESULTS: Toxicological assays showed resistance levels against compounds with different mode of action, with resistance ratios scaling at: 89-fold for abamectin, >1000-fold for clofentezine, >5000-fold etoxazole, 27-fold for fenpyroximate and pyridaben, 20- and 36-fold for spirodiclofen and spirotetramat, respectively and 116- and >500-fold for cyenopyrafen and cyflumetofen, respectively. Bioassays with synergists indicated the involvement of detoxification enzymes in resistance to abamectin but not to cyflumetofen and spirodiclofen. RNAseq analysis showed significant over-expression of several genes encoding detoxification enzymes such as cytochrome P450 monooxygenases and UDP-glycosyltransferases, which have been previously associated with acaricide resistance. Known target-site resistance mutations were identified in acetyl-choline esterase, chitin synthase 1 and NDUFS7/psst, but also discovered putative novel resistance mutations in targets such as the glutamate-gated chloride channel subunit 3. Interestingly, target site resistance mutations against pyrethroids or bifenazate were not identified possibly indicating a recent reduced selection pressure in Greece, as well as a possible opportunity to rotate these chemistries. CONCLUSION: We identified and characterized a striking case of multiple acaricide resistance in a field population of T. urticae. Exceptionally strong resistance phenotypes, with accumulation of multiple resistance mutations and over-expression of P450s and other detoxification genes in the same field population is reported. This article is protected by copyright. All rights reserved.
ESTHER : Papapostolou_2021_Pest.Manag.Sci_77_666
PubMedSearch : Papapostolou_2021_Pest.Manag.Sci_77_666
PubMedID: 33051974
Gene_locus related to this paper: tetur-ACHE

Title : Monitoring and molecular profiling of contemporary insecticide resistance status of malaria vectors in Guinea-Bissau - Silva_2020_Acta.Trop_206_105440
Author(s) : Silva R , Mavridis K , Vontas J , Rodrigues A , Osorio HC
Ref : Acta Trop , 206 :105440 , 2020
Abstract : Despite reduction in the prevalence of malaria, Guinea-Bissau (GB) is still widely affected by the disease that is primarily vectored by Anopheles gambiae s.l. mosquitoes. Monitoring mosquito susceptibility and investigating the insecticide resistance status is an integral part of malaria control actions. Here, mosquito populations from five regions of GB: Bafat, Bissau, Buba, Cacheu and Gabu were monitored for species ID and insecticide resistance, using diagnostic and intensity WHO bioassays, as well as molecular assays. Phenotypic and molecular identification of species showed the presence of An. gambiae s.s. (S form), An. coluzzii (M form) and An. arabiensis, as well as rare An. arabiensis/ An. gambiae hybrids. Resistance to permethrin and deltamethrin was found in all Anopheles populations assayed, with the intensity of resistance for permethrin being moderate to high, as confirmed by bioassays performed at concentration intensities of 5X and 10X. Consistent to these findings, molecular analysis showed a higher frequency of knock-down resistance (kdr) mutations (L1014F, L1014S, reaching > 90% in some areas) compared to previous studies in the same region, as well as detected for the first time the presence of the super kdr mutation (N1575Y) in GB. The "iAche" (G119S) resistance mutation was also found in GB in low frequencies (up to 12.41%). Additionally, the synergistic PBO-permethrin bioassays suggested partial involvement of non target (metabolic and/or reduced penetration) resistance mechanism. Expression analysis of known pyrethroid metabolisers indicated the slight overexpression and possible association of the cytochrome P450s CYP6Z1, CYP4G16 with the pyrethroid resistance phenotype. The findings should guide future evidence-based resistance management strategies in GB.
ESTHER : Silva_2020_Acta.Trop_206_105440
PubMedSearch : Silva_2020_Acta.Trop_206_105440
PubMedID: 32156617

Title : Overexpression of an alternative allele of carboxyl\/choline esterase 4 (CCE04) of Tetranychus urticae is associated with high levels of resistance to the keto-enol acaricide spirodiclofen - Wei_2020_Pest.Manag.Sci_76_1142
Author(s) : Wei P , Demaeght P , De Schutter K , Grigoraki L , Labropoulou V , Riga M , Vontas J , Nauen R , Dermauw W , Van Leeuwen T
Ref : Pest Manag Sci , 76 :1142 , 2020
Abstract : BACKGROUND: Spirodiclofen is an acaricide that targets lipid biosynthesis by inhibiting acetyl-coenzyme A carboxylase. Spirodiclofen resistance in spider mites has been previously documented and was associated with overexpression of CYP392E10, a cytochrome P450 mono-oxygenase that metabolizes spirodiclofen. However, additional mechanisms have been suggested in several studies and a carboxyl/choline esterase gene, CCE04, was shown to be overexpressed in two genetically different strains, SR-VP and SR-TK, both exhibiting high spirodiclofen resistance levels. RESULTS: We identified two different CCE04 alleles in both resistant strains, CCE04(SR-VP) and CCE04(London) , with CCE04(SR-VP) being highly overexpressed. Isoelectric focusing analysis confirmed the overexpression of a single esterase isozyme, while copy number and random fragment length polymorphism analysis revealed that CCE04(SR-VP) overexpression was more likely due to selection for the CCE04(SR-VP) allele rather than gene amplification. Both CCE04 alleles were functionally expressed using the Pichia expression system. Functional enzyme assays revealed only limited kinetic differences between CCE04 isoforms for model substrates. In addition, inhibition/competition experiments with spirodiclofen suggested a similar interaction with both enzymes, whereas its active metabolite, spirodiclofen enol, did not inhibit enzyme activity. CONCLUSION: Our study suggests that selection with spirodiclofen results in enrichment of a specific allele of CCE04 (CCE04(SR-VP) ) in two genetically independent strains, which is highly overexpressed. Based on kinetic enzyme data, however, quantitative rather than qualitative differences between CCE04(SR-VP) and CCE04(London) seem more likely to be involved in resistance. Our findings are discussed in the light of a possible spirodiclofen resistance mechanism, with sequestration of spirodiclofen by CCE04(SR-VP) being a likely hypothesis.
ESTHER : Wei_2020_Pest.Manag.Sci_76_1142
PubMedSearch : Wei_2020_Pest.Manag.Sci_76_1142
PubMedID: 31583806
Gene_locus related to this paper: tetur-t1jsj6 , tetur-t1jth6

Title : Fitness costs of key point mutations that underlie acaricide target-site resistance in the two-spotted spider mite Tetranychus urticae - Bajda_2018_Evol.Appl_11_1540
Author(s) : Bajda S , Riga M , Wybouw N , Papadaki S , Ouranou E , Fotoukkiaii SM , Vontas J , Van Leeuwen T
Ref : Evol Appl , 11 :1540 , 2018
Abstract : The frequency of insecticide/acaricide target-site resistance is increasing in arthropod pest populations and is typically underpinned by single point mutations that affect the binding strength between the insecticide/acaricide and its target-site. Theory predicts that although resistance mutations clearly have advantageous effects under the selection pressure of the insecticide/acaricide, they might convey negative pleiotropic effects on other aspects of fitness. If such fitness costs are in place, target-site resistance is thus likely to disappear in the absence of insecticide/acaricide treatment, a process that would counteract the spread of resistance in agricultural crops. Hence, there is a great need to reliably quantify the various potential pleiotropic effects of target-site resistance point mutations on arthropod fitness. Here, we used near-isogenic lines of the spider mite pest Tetranychus urticae that carry well-characterized acaricide target-site resistance mutations to quantify potential fitness costs. Specifically, we analyzed P262T in the mitochondrial cytochrome b, the combined G314D and G326E substitutions in the glutamate-gated chloride channels, L1024V in the voltage-gated sodium channel, and I1017F in chitin synthase 1. Five fertility life table parameters and nine single-generation life-history traits were quantified and compared across a total of 15 mite lines. In addition, we monitored the temporal resistance level dynamics of populations with different starting frequency levels of the chitin synthase resistant allele to further support our findings. Three target-site resistance mutations, I1017F and the co-occurring G314D and G326E mutations, were shown to significantly and consistently alter certain fitness parameters in T. urticae. The other two mutations (P262T and L1024V) did not result in any consistent change in a fitness parameter analyzed in our study. Our findings are discussed in the context of the global spread of T. urticae pesticide resistance and integrated pest management.
ESTHER : Bajda_2018_Evol.Appl_11_1540
PubMedSearch : Bajda_2018_Evol.Appl_11_1540
PubMedID: 30344626

Title : Molecular characterization of pyrethroid resistance in the olive fruit fly Bactrocera oleae - Pavlidi_2018_Pestic.Biochem.Physiol_148_1
Author(s) : Pavlidi N , Kampouraki A , Tseliou V , Wybouw N , Dermauw W , Roditakis E , Nauen R , Van Leeuwen T , Vontas J
Ref : Pestic Biochem Physiol , 148 :1 , 2018
Abstract : Alpha reduction of pyrethroid efficacy has been recently recorded in Bactrocera oleae, the most destructive insect of olives. The resistance levels of field populations collected from Crete-Greece scaled up to 22-folds, compared to reference laboratory strains. Sequence analysis of the IIS4-IIS6 region of para sodium channel gene in a large number of resistant flies indicated that resistance may not be associated with target site mutations, in line with previous studies in other Tephritidae species. We analyzed the transcriptomic differences between two resistant populations versus an almost susceptible field population and two laboratory strains. A large number of genes was found to be significantly differentially transcribed across the pairwise comparisons. Interestingly, gene set analysis revealed that genes of the 'electron carrier activity' GO group were enriched in one specific comparison, which might suggest a P450-mediated resistance mechanism. The up-regulation of several transcripts encoding detoxification enzymes was qPCR validated, focusing on transcripts coding for P450s. Of note, the expression of contig00436 and contig02103, encoding CYP6 P450s, was significantly higher in all resistant populations, compared to susceptible ones. These results suggest that an increase in the amount of the CYP6 P450s might be an important mechanism of pyrethroid resistance in B. oleae.
ESTHER : Pavlidi_2018_Pestic.Biochem.Physiol_148_1
PubMedSearch : Pavlidi_2018_Pestic.Biochem.Physiol_148_1
PubMedID: 29891359

Title : Ryanodine receptor point mutations confer diamide insecticide resistance in tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae) - Roditakis_2017_Insect.Biochem.Mol.Biol_80_11
Author(s) : Roditakis E , Steinbach D , Moritz G , Vasakis E , Stavrakaki M , Ilias A , Garcia-Vidal L , Martinez-Aguirre MD , Bielza P , Morou E , Silva JE , Silva WM , Siqueira Eta A , Iqbal S , Troczka BJ , Williamson MS , Bass C , Tsagkarakou A , Vontas J , Nauen R
Ref : Insect Biochemistry & Molecular Biology , 80 :11 , 2017
Abstract : Insect ryanodine receptors (RyR) are the molecular target-site for the recently introduced diamide insecticides. Diamides are particularly active on Lepidoptera pests, including tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae). High levels of diamide resistance were recently described in some European populations of T. absoluta, however, the mechanisms of resistance remained unknown. In this study the molecular basis of diamide resistance was investigated in a diamide resistant strain from Italy (IT-GELA-SD4), and additional resistant field populations collected in Greece, Spain and Brazil. The genetics of resistance was investigated by reciprocally crossing strain IT-GELA-SD4 with a susceptible strain and revealed an autosomal incompletely recessive mode of inheritance. To investigate the possible role of target-site mutations as known from diamondback moth (Plutella xylostella), we sequenced respective domains of the RyR gene of T. absoluta. Genotyping of individuals of IT-GELA-SD4 and field-collected strains showing different levels of diamide resistance revealed the presence of G4903E and I4746M RyR target-site mutations. These amino acid substitutions correspond to those recently described for diamide resistant diamondback moth, i.e. G4946E and I4790M. We also detected two novel mutations, G4903V and I4746T, in some of the resistant T. absoluta strains. Radioligand binding studies with thoracic membrane preparations of the IT-GELA-SD4 strain provided functional evidence that these mutations alter the affinity of the RyR to diamides. In combination with previous work on P. xylostella our study highlights the importance of position G4903 (G4946 in P. xylostella) of the insect RyR in defining sensitivity to diamides. The discovery of diamide resistance mutations in T. absoluta populations of diverse geographic origin has serious implications for the efficacy of diamides under applied conditions. The implementation of appropriate resistance management strategies is strongly advised to delay the further spread of resistance.
ESTHER : Roditakis_2017_Insect.Biochem.Mol.Biol_80_11
PubMedSearch : Roditakis_2017_Insect.Biochem.Mol.Biol_80_11
PubMedID: 27845250

Title : Analysis of population structure and insecticide resistance in mosquitoes of the genus Culex, Anopheles and Aedes from different environments of Greece with a history of mosquito borne disease transmission - Fotakis_2017_Acta.Trop_174_29
Author(s) : Fotakis EA , Chaskopoulou A , Grigoraki L , Tsiamantas A , Kounadi S , Georgiou L , Vontas J
Ref : Acta Trop , 174 :29 , 2017
Abstract : Greece has been recently affected by several mosquito borne diseases with the West Nile Virus (WNV) outbreak in 2010 being one of the largest reported in Europe. Currently at the epicenter of an economic and refugee crisis and visited by over 16 million tourists a year the integrated management of diseases transmitted by mosquitoes is a public health and economic priority. Vector control programs rely mainly on insecticides, however data on insecticide resistance and the mosquito fauna is essential for successful applications. We determined the mosquito species composition and population dynamics in areas of increased vulnerability to vector borne disease transmission, as well as investigated the resistance status of major nuisance and disease vectors to insecticides. High mosquito densities were recorded in Thessaloniki and Evros, with Aedes caspius, a nuisance species, Culex pipiens, a known vector of WNV and Anopheles hyrcanus a potential vector of malaria being among the most prevalent species. Both vector species populations reached their peak in late summer. Aedes albopictus was recorded at high densities in Thessaloniki, but not in Evros. Notably, Cx. pipiens hybrids, which show an opportunistic biting behavior and are suspected to be involved in the transmission of the WNV, were recorded in considerable numbers in Thessaloniki and Attica. Culex pipiens and An. hyrcanus, but not Ae. caspius mosquitoes, showed moderate levels of resistance to deltamethrin. The presence of resistance in areas not exposed to vector control indicates that other factors could be selecting for resistance, i.e. pesticide applications for agriculture. Both L1014F and L101C kdr mutations were detected in Cx. pipiens populations. Anopheles hyrcanus resistance was not associated with mutations at the L1014 site. The Ace-1 mutations conferring insensitivity to organophosphates and carbamates were detected at low frequencies in all Cx. pipiens populations. Increased activity of P450s and esterases was found in Cx. pipiens individuals from Thessaloniki. Our study contributes evidence for sustainable and efficient vector control strategies and the prevention of disease outbreaks.
ESTHER : Fotakis_2017_Acta.Trop_174_29
PubMedSearch : Fotakis_2017_Acta.Trop_174_29
PubMedID: 28606820

Title : The relative contribution of target-site mutations in complex acaricide resistant phenotypes as assessed by marker assisted backcrossing in Tetranychus urticae - Riga_2017_Sci.Rep_7_9202
Author(s) : Riga M , Bajda S , Themistokleous C , Papadaki S , Palzewicz M , Dermauw W , Vontas J , Leeuwen TV
Ref : Sci Rep , 7 :9202 , 2017
Abstract : The mechanisms underlying insecticide and acaricide resistance in insects and mites are often complex, including additive effects of target-site insensitivity, increased metabolism and transport. The extent to which target-site resistance mutations contribute to the resistance phenotype is, however, not well studied. Here, we used marker-assisted backcrossing to create 30 congenic lines carrying nine mutations (alone, or in combination in a few cases) associated with resistance to avermectins, pyrethroids, mite growth inhibitors and mitochondrial complex III inhibitors (QoI) in a polyphagous arthropod pest, the spider mite Tetranychus urticae. Toxicity tests revealed that mutations in the voltage-gated sodium channel, chitin synthase 1 and cytochrome b confer high levels of resistance and, when fixed in a population, these mutations alone can result in field failure of acaricide treatment. In contrast, although we confirmed the implication of mutations in glutamate-gated chloride channels in abamectin and milbemectin insensitivity, these mutations do not lead to the high resistance levels that are often reported in abamectin resistant strains of T. urticae. Overall, this study functionally validates reported target-site resistance mutations in T. urticae, by uncoupling them from additional mechanisms, allowing to finally investigate the strength of the conferred phenotype in vivo.
ESTHER : Riga_2017_Sci.Rep_7_9202
PubMedSearch : Riga_2017_Sci.Rep_7_9202
PubMedID: 28835683

Title : Identification and detection of indoxacarb resistance mutations in the para sodium channel of the tomato leafminer, Tuta absoluta - Roditakis_2017_Pest.Manag.Sci_73_1679
Author(s) : Roditakis E , Mavridis K , Riga M , Vasakis E , Morou E , Rison JL , Vontas J
Ref : Pest Manag Sci , 73 :1679 , 2017
Abstract : BACKGROUND: Indoxacarb is an important active ingredient extensively used for the control of Tuta absoluta, a major tomato pest, playing a particular role in insecticide resistance management schemes.
RESULTS: Reduced susceptibility to indoxacarb was identified (1794-fold resistance) through toxicological bioassays in a field population from Greece and evolved rapidly to resistance after short laboratory selection. Combined bioassays with synergists and biochemical analysis suggested only a partial involvement of detoxification enzymes in the resistant phenotype. To investigate the role of target-site resistance, segment 6 of domain IV of the sodium channel in T. absoluta was cloned and the sequences compared between susceptible and indoxacarb-resistant T. absoluta insects. The presence of the F1845Y and the V1848I indoxacarb resistance mutations was detected and was strongly associated with the phenotype. These amino acid substitutions correspond to recently characterised indoxacarb resistance mutations in diamondback moth (Plutella xylostella). Robust and accurate PCR-RFLP assays were subsequently developed and successfully validated for detecting both indoxacarb resistance mutations in field T. absoluta populations. CONCLUSION: The identification of indoxacarb resistance mutations and the development of diagnostic tools will allow early detection of indoxacarb resistance, facilitating implementation of appropriate resistance management strategies, thus delaying the spread of resistance. (c) 2016 Society of Chemical Industry.
ESTHER : Roditakis_2017_Pest.Manag.Sci_73_1679
PubMedSearch : Roditakis_2017_Pest.Manag.Sci_73_1679
PubMedID: 28019074

Title : Carboxylesterase gene amplifications associated with insecticide resistance in Aedes albopictus: Geographical distribution and evolutionary origin - Grigoraki_2017_PLoS.Negl.Trop.Dis_11_e0005533
Author(s) : Grigoraki L , Pipini D , Labbe P , Chaskopoulou A , Weill M , Vontas J
Ref : PLoS Negl Trop Dis , 11 :e0005533 , 2017
Abstract : BACKGROUND: Aedes albopictus is one of the most invasive human disease vectors. Its control has been largely based on insecticides, such as the larvicide temephos. Temephos resistance has been associated with the up-regulation, through gene amplification, of two carboxylesterase (CCE) genes closely linked on the genome, capable of sequestering and metabolizing temephos oxon, the activated form of temephos. PRINCIPAL FINDINGS: Here, we investigated the occurrence, geographical distribution and origin of the CCE amplicon in Ae. albopictus populations from several geographical regions worldwide. The haplotypic diversity at the CCEae3a locus revealed high polymorphism, while phylogenetic analysis showed an absence of correlation between haplotype similarity and geographic origin. Two types of esterase amplifications were found, in two locations only (Athens and Florida): one, previously described, results in the amplification of both CCEae3a and CCEae6a; the second is being described for the first time and results in the amplification of CCEae3a only. The two amplification events are independent, as confirmed by sequence analysis. All individuals from Athens and Florida carrying the CCEae3a-CCEae6a co-amplicon share a common haplotype, indicating a single amplification event, which spread between the two countries. SIGNIFICANCE: The importance of passive transportation of disease vectors, including individuals carrying resistance mechanisms, is discussed in the light of efficient and sustainable vector control strategies.
ESTHER : Grigoraki_2017_PLoS.Negl.Trop.Dis_11_e0005533
PubMedSearch : Grigoraki_2017_PLoS.Negl.Trop.Dis_11_e0005533
PubMedID: 28394886
Gene_locus related to this paper: aedae-q17b28 , aedae-q17b31

Title : Functional and immunohistochemical characterization of CCEae3a, a carboxylesterase associated with temephos resistance in the major arbovirus vectors Aedes aegypti and Ae. albopictus - Grigoraki_2016_Insect.Biochem.Mol.Biol_74_61
Author(s) : Grigoraki L , Balabanidou V , Meristoudis C , Myridakis A , Ranson H , Swevers L , Vontas J
Ref : Insect Biochemistry & Molecular Biology , 74 :61 , 2016
Abstract : Temephos is a major organophosphate (OP) larvicide that has been used extensively for the control of Aedes albopictus and Aedes aegypti, the major vectors for viral diseases, such as dengue fever, zika and chikungunya. Resistance to temephos has been recently detected and associated with the upregulation of carboxylesterases (CCEs) through gene amplification, in both species. Here, we expressed the CCEae3a genes which showed the most striking up-regulation in resistant Aedes strains, using the baculovirus system. All CCEae3a variants encoded functional enzymes, with high activity and preference for p-nitrophenyl butyrate, a substrate that was shown capable to differentiate temephos resistant from susceptible Aedes larvae. Enzyme kinetic studies showed that CCEae3as from both Ae. aegypti and Ae. albopictus (CCEae3a_aeg and CCEae3a_alb, respectively) strongly interact with temephos oxon and slowly released the OP molecule, indicating a sequestration resistance mechanism. No difference was detected between resistant and susceptible CCEae3a_aeg variants (CCEae3a_aegR and CCEae3a_aegS, respectively), indicating that previously reported polymorphism is unlikely to play a role in temephos resistance. HPLC/MS showed that CCEae3as were able to metabolize temephos oxon to the temephos monoester [(4-hydroxyphenyl) sulfanyl] phenyl O,O-dimethylphosphorothioate. Western blot and immunolocalization studies, based on a specific antibody raised against the CCEae3a_alb showed that the enzyme is expressed at higher levels in resistant insects, primarily in malpighian tubules (MT) and nerve tissues.
ESTHER : Grigoraki_2016_Insect.Biochem.Mol.Biol_74_61
PubMedSearch : Grigoraki_2016_Insect.Biochem.Mol.Biol_74_61
PubMedID: 27180726
Gene_locus related to this paper: aedae-q17b28 , aedae-q17b31

Title : Identification of a point mutation in the ace1 gene of Therioaphis trifolli maculata and detection of insecticide resistance by a diagnostic PCR-RFLP assay - AlSuhaibani_2015_Bull.Entomol.Res_105_712
Author(s) : AlSuhaibani E , Voudouris CC , Al-Atiyat R , Kotzamumin A , Vontas J , Margaritopoulos JT
Ref : Bull Entomol Res , 105 :712 , 2015
Abstract : Aphids are important agricultural pests worldwide. Their control is largely based on chemical insecticides. One species that shows important invasive abilities and host-plant-related differences is Therioaphis trifolii (Monell) (Hemiptera: Aphididae). T. trifolii maculata, also known as spotted alfalfa aphid (SAA), can be very injurious to alfalfa crops in certain regions, such as in Saudi Arabia for effective control it is essential to diagnose and monitor the resistance mechanisms in the SAA populations. In the present study, we analysed acetylcholinesterase (ace) target site insensitivity mechanisms. A 650 bp length DNA containing the putative acetylcholinesterase (ace1) precursor was obtained and compared with other Hemipteran species. The sequences of many individual aphids collected from alfalfa crops in Saudi Arabia were analysed for the presence of resistance mutations: no resistance mutations were found at the resistance mutation loci 302; however, the presence of a serine-phenylalanine substitution (S431F) was identified in one individual. The S431F substitution, has been shown to confer significant levels of both organophosphate and carbamate resistance in other aphid species, and is now found for the first time in T. trifolii. We subsequently developed a simple polymerase chain reaction-restriction fragment length polymorphism assays for the S431F mutation, using a TaqI restriction site destroyed by the S431F mutation. The novel diagnostic assay may support the implementation of Insecticide Resistance Management strategies, for the control of SAA in alfalfa crops in the Kingdom of Saudi Arabia, and other countries worldwide.
ESTHER : AlSuhaibani_2015_Bull.Entomol.Res_105_712
PubMedSearch : AlSuhaibani_2015_Bull.Entomol.Res_105_712
PubMedID: 26278202

Title : Transcriptome Profiling and Genetic Study Reveal Amplified Carboxylesterase Genes Implicated in Temephos Resistance, in the Asian Tiger Mosquito Aedes albopictus - Grigoraki_2015_PLoS.Negl.Trop.Dis_9_e0003771
Author(s) : Grigoraki L , Lagnel J , Kioulos I , Kampouraki A , Morou E , Labbe P , Weill M , Vontas J
Ref : PLoS Negl Trop Dis , 9 :e0003771 , 2015
Abstract : BACKGROUND: The control of Aedes albopictus, a major vector for viral diseases, such as dengue fever and chikungunya, has been largely reliant on the use of the larvicide temephos for many decades. This insecticide remains a primary control tool for several countries and it is a potential reliable reserve, for emergency epidemics or new invasion cases, in regions such as Europe which have banned its use. Resistance to temephos has been detected in some regions, but the mechanism responsible for the trait has not been investigated. PRINCIPAL FINDINGS: Temephos resistance was identified in an Aedes albopictus population isolated from Greece, and subsequently selected in the laboratory for a few generations. Biochemical assays suggested the association of elevated carboxylesterases (CCE), but not target site resistance (altered AChE), with this phenotype. Illumina transcriptomic analysis revealed the up-regulation of three transcripts encoding CCE genes in the temephos resistant strain. CCEae3a and CCEae6a showed the most striking up-regulation (27- and 12-folds respectively, compared to the reference susceptible strain); these genes have been previously shown to be involved in temephos resistance also in Ae. aegypti. Gene amplification was associated with elevated transcription levels of both CCEae6a and CCEae3a genes. Genetic crosses confirmed the genetic link between CCEae6a and CCEae3a amplification and temephos resistance, by demonstrating a strong association between survival to temephos exposure and gene copy numbers in the F2 generation. Other transcripts, encoding cytochrome P450s, UDP-glycosyltransferases (UGTs), cuticle and lipid biosynthesis proteins, were upregulated in resistant mosquitoes, indicating that the co-evolution of multiple mechanisms might contribute to resistance. SIGNIFICANCE: The identification of specific genes associated with insecticide resistance in Ae. albopictus for the first time is an important pre-requirement for insecticide resistance management. The genomic resources that were produced will be useful to the community, to study relevant aspects of Ae. albopictus biology.
ESTHER : Grigoraki_2015_PLoS.Negl.Trop.Dis_9_e0003771
PubMedSearch : Grigoraki_2015_PLoS.Negl.Trop.Dis_9_e0003771
PubMedID: 26000638
Gene_locus related to this paper: aedae-q17b28 , aedae-q17b31

Title : Genome sequence of the Asian Tiger mosquito, Aedes albopictus, reveals insights into its biology, genetics, and evolution - Chen_2015_Proc.Natl.Acad.Sci.U.S.A_112_E5907
Author(s) : Chen XG , Jiang X , Gu J , Xu M , Wu Y , Deng Y , Zhang C , Bonizzoni M , Dermauw W , Vontas J , Armbruster P , Huang X , Yang Y , Zhang H , He W , Peng H , Liu Y , Wu K , Chen J , Lirakis M , Topalis P , Van Leeuwen T , Hall AB , Thorpe C , Mueller RL , Sun C , Waterhouse RM , Yan G , Tu ZJ , Fang X , James AA
Ref : Proc Natl Acad Sci U S A , 112 :E5907 , 2015
Abstract : The Asian tiger mosquito, Aedes albopictus, is a highly successful invasive species that transmits a number of human viral diseases, including dengue and Chikungunya fevers. This species has a large genome with significant population-based size variation. The complete genome sequence was determined for the Foshan strain, an established laboratory colony derived from wild mosquitoes from southeastern China, a region within the historical range of the origin of the species. The genome comprises 1,967 Mb, the largest mosquito genome sequenced to date, and its size results principally from an abundance of repetitive DNA classes. In addition, expansions of the numbers of members in gene families involved in insecticide-resistance mechanisms, diapause, sex determination, immunity, and olfaction also contribute to the larger size. Portions of integrated flavivirus-like genomes support a shared evolutionary history of association of these viruses with their vector. The large genome repertory may contribute to the adaptability and success of Ae. albopictus as an invasive species.
ESTHER : Chen_2015_Proc.Natl.Acad.Sci.U.S.A_112_E5907
PubMedSearch : Chen_2015_Proc.Natl.Acad.Sci.U.S.A_112_E5907
PubMedID: 26483478
Gene_locus related to this paper: aedae-q177c7 , aedal-a0a182gwe3 , aedal-a0a182gwt8 , aedal-a0a023eq67

Title : Dissecting the organ specificity of insecticide resistance candidate genes in Anopheles gambiae: known and novel candidate genes - Ingham_2014_BMC.Genomics_15_1018
Author(s) : Ingham VA , Jones CM , Pignatelli P , Balabanidou V , Vontas J , Wagstaff SC , Moore JD , Ranson H
Ref : BMC Genomics , 15 :1018 , 2014
Abstract : BACKGROUND: The elevated expression of enzymes with insecticide metabolism activity can lead to high levels of insecticide resistance in the malaria vector, Anopheles gambiae. In this study, adult female mosquitoes from an insecticide susceptible and resistant strain were dissected into four different body parts. RNA from each of these samples was used in microarray analysis to determine the enrichment patterns of the key detoxification gene families within the mosquito and to identify additional candidate insecticide resistance genes that may have been overlooked in previous experiments on whole organisms.
RESULTS: A general enrichment in the transcription of genes from the four major detoxification gene families (carboxylesterases, glutathione transferases, UDP glucornyltransferases and cytochrome P450s) was observed in the midgut and malpighian tubules. Yet the subset of P450 genes that have previously been implicated in insecticide resistance in An gambiae, show a surprisingly varied profile of tissue enrichment, confirmed by qPCR and, for three candidates, by immunostaining. A stringent selection process was used to define a list of 105 genes that are significantly (p </=0.001) over expressed in body parts from the resistant versus susceptible strain. Over half of these, including all the cytochrome P450s on this list, were identified in previous whole organism comparisons between the strains, but several new candidates were detected, notably from comparisons of the transcriptomes from dissected abdomen integuments.
CONCLUSIONS: The use of RNA extracted from the whole organism to identify candidate insecticide resistance genes has a risk of missing candidates if key genes responsible for the phenotype have restricted expression within the body and/or are over expression only in certain tissues. However, as transcription of genes implicated in metabolic resistance to insecticides is not enriched in any one single organ, comparison of the transcriptome of individual dissected body parts cannot be recommended as a preferred means to identify new candidate insecticide resistant genes. Instead the rich data set on in vivo sites of transcription should be consulted when designing follow up qPCR validation steps, or for screening known candidates in field populations.
ESTHER : Ingham_2014_BMC.Genomics_15_1018
PubMedSearch : Ingham_2014_BMC.Genomics_15_1018
PubMedID: 25421852

Title : Global distribution and origin of target site insecticide resistance mutations in Tetranychus urticae - Ilias_2014_Insect.Biochem.Mol.Biol_48_17
Author(s) : Ilias A , Vontas J , Tsagkarakou A
Ref : Insect Biochemistry & Molecular Biology , 48 :17 , 2014
Abstract : The control of Tetranychus urticae, a worldwide agricultural pest, is largely dependent on pesticides. However, their efficacy is often compromised by the development of resistance. Recent molecular studies identified a number of target site resistance mutations, such as G119S, A201S, T280A, G328A, F331W in the acetylcholinesterase gene, L1024V, A1215D, F1538I in the voltage-gated sodium channel gene, G314D and G326E in glutamate-gated chloride channel genes, G126S, I136T, S141F, D161G, P262T in the cytochrome b and the I1017F in the chitin synthase 1 gene. We examined their distribution, by sequencing the relevant gene fragments in a large number of T. urticae collections from a wide geographic range. Our study revealed that most of the resistance mutations are spread worldwide, with remarkably variable frequencies. Furthermore, we analyzed the variability of the ace locus, which has been subjected to longer periods of selection pressure historically, to investigate the evolutionary origin of ace resistant alleles and determine whether they resulted from single or multiple mutation events. By sequencing a 1540 bp ace fragment, encompassing the resistance mutations and downstream introns in 139 T. urticae individuals from 27 countries, we identified 6 susceptible and 31 resistant alleles which have arisen from at least three independent mutation events. The frequency and distribution of these ace haplotypes varied geographically, suggesting an interplay between different mutational events, gene flow and local selection.
ESTHER : Ilias_2014_Insect.Biochem.Mol.Biol_48_17
PubMedSearch : Ilias_2014_Insect.Biochem.Mol.Biol_48_17
PubMedID: 24602758
Gene_locus related to this paper: tetur-ACHE

Title : Molecular analysis of resistance to acaricidal spirocyclic tetronic acids in Tetranychus urticae: CYP392E10 metabolizes spirodiclofen, but not its corresponding enol - Demaeght_2013_Insect.Biochem.Mol.Biol_43_544
Author(s) : Demaeght P , Dermauw W , Tsakireli D , Khajehali J , Nauen R , Tirry L , Vontas J , Lummen P , Van Leeuwen T
Ref : Insect Biochemistry & Molecular Biology , 43 :544 , 2013
Abstract : Spirodiclofen is one of the most recently developed acaricides and belongs to the new family of spirocyclic tetronic acids (ketoenols). This new acaricidal family is an important chemical tool in resistance management strategies providing sustainable control of spider mites such as Tetranychus urticae. Spirodiclofen targets lipid biosynthesis mediated by direct inhibition of acetyl coenzyme A carboxylase (ACCase). In this study, we investigated two genetically distant spider mite strains with high resistance to spirodiclofen. Despite the strong resistance levels to spirodiclofen (up to 680-fold), only limited cross-resistance with other members of this group such as spiromesifen and spirotetramat could be detected. Amplification and sequencing of the ACCase gene from resistant and susceptible strains did not reveal common non-synonymous mutations, and expression levels of ACCase were similar in both resistant and susceptible strains, indicating the absence of target-site resistance. Furthermore, we collected genome-wide expression data of susceptible and resistant T. urticae strains using microarray technology. Analysis of differentially expressed genes revealed a broad response, but within the overlap of two resistant strains, several cytochrome P450s were prominent. Quantitative PCR confirmed the constitutive over-expression of CYP392E7 and CYP392E10 in resistant strains, and CYP392E10 expression was highly induced by spirodiclofen. Furthermore, stage specific expression profiling revealed that expression levels were not significantly different between developing stages, but very low in eggs, matching the age-dependent resistance pattern previously observed. Functional expression of CYP392E7 and CYP392E10 confirmed that CYP392E10 (but not CYP392E7) metabolizes spirodiclofen by hydroxylation as identified by LC-MS/MS, and revealed cooperative substrate binding and a Km of 43 muM spirodiclofen. CYP392E10 also metabolizes spiromesifen, but not spirotetramat. Surprisingly, no metabolism of the hydrolyzed spirodiclofen-enol metabolite could be detected. These findings are discussed in the light of a likely resistance mechanism.
ESTHER : Demaeght_2013_Insect.Biochem.Mol.Biol_43_544
PubMedSearch : Demaeght_2013_Insect.Biochem.Mol.Biol_43_544
PubMedID: 23523619

Title : Country-level operational implementation of the Global Plan for Insecticide Resistance Management - Hemingway_2013_Proc.Natl.Acad.Sci.U.S.A_110_9397
Author(s) : Hemingway J , Vontas J , Poupardin R , Raman J , Lines J , Schwabe C , Matias A , Kleinschmidt I
Ref : Proc Natl Acad Sci U S A , 110 :9397 , 2013
Abstract : Malaria control is reliant on the use of long-lasting pyrethroid-impregnated nets and/or indoor residual spraying (IRS) of insecticide. The rapid selection and spread of operationally significant pyrethroid resistance in African malaria vectors threatens our ability to sustain malaria control. Establishing whether resistance is operationally significant is technically challenging. Routine monitoring by bioassay is inadequate, and there are limited data linking resistance selection with changes in disease transmission. The default is to switch insecticides when resistance is detected, but limited insecticide options and resistance to multiple insecticides in numerous locations make this approach unsustainable. Detailed analysis of the resistance situation in Anopheles gambiae on Bioko Island after pyrethroid resistance was detected in this species in 2004, and the IRS program switched to carbamate bendiocarb, has now been undertaken. The pyrethroid resistance selected is a target-site knock-down resistance kdr-form, on a background of generally elevated metabolic activity, compared with insecticide-susceptible A. gambiae, but the major cytochrome P450-based metabolic pyrethroid resistance mechanisms are not present. The available evidence from bioassays and infection data suggests that the pyrethroid resistance mechanisms in Bioko malaria vectors are not operationally significant, and on this basis, a different, long-lasting pyrethroid formulation is now being reintroduced for IRS in a rotational insecticide resistance management program. This will allow control efforts to be sustained in a cost-effective manner while reducing the selection pressure for resistance to nonpyrethroid insecticides. The methods used provide a template for evidence-based insecticide resistance management by malaria control programs.
ESTHER : Hemingway_2013_Proc.Natl.Acad.Sci.U.S.A_110_9397
PubMedSearch : Hemingway_2013_Proc.Natl.Acad.Sci.U.S.A_110_9397
PubMedID: 23696658

Title : Insecticide resistance in the major dengue vectors Aedes albopictus and Aedes aegypti - Vontas_2012_Pestic.Biochem.Physiol_104_126
Author(s) : Vontas J , Kioulos E , Pavlidi N , Morou E , della Torre A , Ranson H
Ref : , 104 :126 , 2012
Abstract : Aedes mosquitoes are major vectors of human diseases, such as the dengue fever, chikungunya and yellow fever. Their control largely relies on insecticides applied to mosquito larvae habitats, or indoors against adult mosquitoes. However, insecticide resistance has evolved in many Aedes aegypti mosquito populations worldwide and there is evidence that it has compromised the success of control interventions. The levels of resistance in Aedes albopictus is relatively low at present compared to Ae. aegypti, possibly due to the reduced exposure of this more exophilic species to insecticides, particularly those targeting the adult stage. This paper reviews Ae. albopictus susceptibility/resistance status, as well as reports some new bioassay data from European populations (Greece and Italy). The most recent molecular research into Ae. aegypti insecticide resistance mechanisms is also reviewed, with emphasis on neurotoxic insecticides.
ESTHER : Vontas_2012_Pestic.Biochem.Physiol_104_126
PubMedSearch : Vontas_2012_Pestic.Biochem.Physiol_104_126

Title : Development of high-throughput real-time PCR assays for the identification of insensitive acetylcholinesterase (ace-1R) in Anopheles gambiae - Bass_2010_Pestic.Biochem.Physiol_96_80
Author(s) : Bass C , Nikou D , Vontas J , Williamson MS , Field LM
Ref : Pesticide Biochemistry and Physiology , 96 :80 , 2010
Abstract : Resistance to the organophosphate and carbamate insecticides through insensitivity of the target site enzyme, acetylcholinesterase has recently been reported in Anopheles gambiae populations in West Africa. To date, screening for the mutation (G119S of the ace-1 gene) conferring this insensitivity has employed a simple PCR-RFLP diagnostic. However, this has the disadvantage of requiring digestion of the amplified fragment and subsequent gel electrophoresis of the products. To overcome this, and thus increase throughput and reduce costs, we have developed two assays based on real-time PCR (TaqMan and melt-curve) that represent true [`]closed-tube' approaches. The two new platforms were compared to PCR-RFLP to genotype over 280 samples. The two new methods compared favourably with PCR-RFLP with the TaqMan assay delivering the greatest specificity and sensitivity of the three approaches. This assay is also cheaper to run than PCR-RFLP and results are obtained in a single step.
ESTHER : Bass_2010_Pestic.Biochem.Physiol_96_80
PubMedSearch : Bass_2010_Pestic.Biochem.Physiol_96_80
Gene_locus related to this paper: anoga-ACHE1

Title : Acetylcholinesterase point mutations in European strains of Tetranychus urticae (Acari: Tetranychidae) resistant to organophosphates - Khajehali_2010_Pest.Manag.Sci_66_220
Author(s) : Khajehali J , Van Leeuwen T , Grispou M , Morou E , Alout H , Weill M , Tirry L , Vontas J , Tsagkarakou A
Ref : Pest Manag Sci , 66 :220 , 2010
Abstract : BACKGROUND: In Tetranychus urticae Koch, acetylcholinesterase insensitivity is often involved in organophosphate (OP) and carbamate (CARB) resistance. By combining toxicological, biochemical and molecular data from three reference laboratory and three OP selected strains (OP strains), the AChE1 mutations associated with resistance in T. urticae were characterised. RESULTS: The resistance ratios of the OP strains varied from 9 to 43 for pirimiphos-methyl, from 78 to 586 for chlorpyrifos, from 8 to 333 for methomyl and from 137 to 4164 for dimethoate. The insecticide concentration needed to inhibit 50% of the AChE1 activity was, in the OP strains, at least 2.7, 55, 58 and 31 times higher for the OP pirimiphos-methyl, chlorpyrifos oxon, paraoxon and omethoate respectively, and 87 times higher for the CARB carbaryl. By comparing the AChE1 sequence, four amino acid substitutions were detected in the OP strains: (1) F331W (Torpedo numbering) in all the three OP strains; (2) T280A found in the three OP strains but not in all clones; (3) G328A, found in two OP strains; (4) A201S found in only one OP strain. CONCLUSIONS: Four AChE1 mutations were found in resistant strains of T. urticae, and three of them, F331W, G328A and A201S, are possibly involved in resistance to OP and CARB insecticides. Among them, F331W is probably the most important and the most common in T. urticae. It can be easily detected by the diagnostic PCR-RLFP assay developed in this study.
ESTHER : Khajehali_2010_Pest.Manag.Sci_66_220
PubMedSearch : Khajehali_2010_Pest.Manag.Sci_66_220
PubMedID: 19894225
Gene_locus related to this paper: tetur-ACHE

Title : Acaricide resistance mechanisms in the two-spotted spider mite Tetranychus urticae and other important Acari: a review - Van Leeuwen_2010_Insect.Biochem.Mol.Biol_40_563
Author(s) : Van Leeuwen T , Vontas J , Tsagkarakou A , Dermauw W , Tirry L
Ref : Insect Biochemistry & Molecular Biology , 40 :563 , 2010
Abstract : The two-spotted spider mite Tetranychus urticae Koch is one of the economically most important pests in a wide range of outdoor and protected crops worldwide. Its control has been and still is largely based on the use of insecticides and acaricides. However, due to its short life cycle, abundant progeny and arrhenotokous reproduction, it is able to develop resistance to these compounds very rapidly. As a consequence, it has the dubious reputation to be the"most resistant species" in terms of the total number of pesticides to which populations have become resistant, and its control has become problematic in many areas worldwide. Insecticide and acaricide resistance has also been reported in the ectoparasite Sarcoptes scabiei, the causative organism of scabies, and other economically important Acari, such as the Southern cattle tick Rhipicephalus microplus, one of the biggest arthropod threats to livestock, and the parasitic mite Varroa destructor, a major economic burden for beekeepers worldwide. Although resistance research in Acari has not kept pace with that in insects, a number of studies on the molecular mechanisms responsible for the resistant phenotype has been conducted recently. In this review, state-of-the-art information on T. urticae resistance, supplemented with data on other important Acari has been brought together. Considerable attention is given to the underlying resistance mechanisms that have been elucidated at the molecular level. The incidence of bifenazate resistance in T. urticae is expanded as an insecticide resistance evolutionary paradigm in arthropods.
ESTHER : Van Leeuwen_2010_Insect.Biochem.Mol.Biol_40_563
PubMedSearch : Van Leeuwen_2010_Insect.Biochem.Mol.Biol_40_563
PubMedID: 20685616

Title : Short report: a multiplex PCR assay for simultaneous genotyping of kdr and ace-1 loci in Anopheles gambiae - Kazanidou_2009_Am.J.Trop.Med.Hyg_80_236
Author(s) : Kazanidou A , Nikou D , Grigoriou M , Vontas J , Skavdis G
Ref : American Journal of Tropical Medicine & Hygiene , 80 :236 , 2009
Abstract : The selection of insecticide-resistant genotypes in Anopheles gambiae, the most important malaria vector in Africa, makes disease control problematic in several endemic areas. The early detection and monitoring of resistance associated mutations in field mosquito populations is essential for the application of successful insecticide-based control interventions. Currently, the surveillance of these mutations is performed using individual assays, some of which require sophisticated and expensive equipment. Here we describe a novel multiplex polymerase chain reaction-based assay for detecting simultaneously the five single nucleotide polymorphisms in the voltage-gated sodium channel and the ace-1 genes, which have been associated with the mosquito response to most commonly used insecticides.
ESTHER : Kazanidou_2009_Am.J.Trop.Med.Hyg_80_236
PubMedSearch : Kazanidou_2009_Am.J.Trop.Med.Hyg_80_236
PubMedID: 19190219

Title : Current status of insecticide resistance in Q biotype Bemisia tabaci populations from Crete - Roditakis_2009_Pest.Manag.Sci_65_313
Author(s) : Roditakis E , Grispou M , Morou E , Kristoffersen JB , Roditakis N , Nauen R , Vontas J , Tsagkarakou A
Ref : Pest Manag Sci , 65 :313 , 2009
Abstract : BACKGROUND: A major problem of crop protection in Crete, Greece, is the control of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) with chemical insecticides owing to the rapid development of resistance. The aim of this study was to investigate the establishment of resistance and the underlying mechanisms to major insecticide classes with classical bioassays and known biochemical resistance markers. RESULTS: During a 2005-2007 survey, 53 Q biotype populations were collected. Application history records showed extensive use of neonicotinoids, organophosphates, carbamates and pyrethroids. High resistance levels were identified in the majority of populations (>80%) for imidacloprid (RF: 38-1958x) and alpha-cypermethrin (RF: 30-600x). Low resistance levels (RF < 12) were observed for pirimiphos-methyl. A strong correlation between resistance to imidacloprid and the number of applications with neonicotinoids was observed. Significant correlations were observed between COE and P450-dependent monoxygenase activity with resistance to alpha-cypermethrin and imidacloprid respectively. A propoxur-based AChE diagnostic test indicated that iAChE was widespread in most populations. Resistance levels for alpha-cypermethrin were increased when compared with a previous survey (2002-2003). Differentiation of LC(50) values between localities was observed for imidacloprid only. CONCLUSION: Bemisia tabaci resistance evolved differently in each of the three insecticides studied. Imidacloprid resistance seems less established and less persistent than alpha-cypermethrin resistance. The low resistance levels for pirimiphos-methyl suggest absence of cross-resistance with other organophosphates or carbamates used.
ESTHER : Roditakis_2009_Pest.Manag.Sci_65_313
PubMedSearch : Roditakis_2009_Pest.Manag.Sci_65_313
PubMedID: 19115232

Title : Molecular diagnostics for detecting pyrethroid and organophosphate resistance mutations in the Q biotype of the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) - Tsagkarakou_2010_Pestic.Biochem.Physiol_94_49
Author(s) : Tsagkarakou A , Nikou Dimitra , Roditakis E , Sharvit M , Morin S , Vontas J
Ref : Pesticide Biochemistry and Physiology , 94 :49 , 2009
Abstract : Pyrethroid and organophosphate resistance-associated mutations have been recently reported in the whitefly Bemisia tabaci (Gennadius), a major pest of protected and outdoor crops worldwide. Here, we developed simple PCR-agarose gel visualization based assays for reliably monitoring the L925I and T929V pyrethroid resistance mutations in the B. tabaci para-type voltage gated sodium channel and the iAChE F331W organophosphate resistance mutation in the acetylcholinesterase enzyme ace1. PCR-RFLP assays were developed for detecting the L925I and the F331W resistance mutations. A highly specific PASA was developed for detecting the T929V mutation. The molecular diagnostic tools were used to monitor the frequency of the resistance mutations in a large number of field caught Q biotype B. tabaci from Crete (Greece), where both organophosphates and pyrethroids are extensively used. The F331W mutation was fixed in all field individuals examined. The pyrethroid resistance mutations were detected in high frequencies: 0.38 and 0.54 for L925I and T929V, respectively. The simple diagnostics are accurate and robust, to be used alongside classical bioassays to prevent ineffective insecticide applications, and for early identification of the spreading of resistant Q biotype populations into new regions around the globe.
ESTHER : Tsagkarakou_2010_Pestic.Biochem.Physiol_94_49
PubMedSearch : Tsagkarakou_2010_Pestic.Biochem.Physiol_94_49
Gene_locus related to this paper: bemta-ACHE1

Title : Cross-induction of detoxification genes by environmental xenobiotics and insecticides in the mosquito Aedes aegypti: impact on larval tolerance to chemical insecticides - Poupardin_2008_Insect.Biochem.Mol.Biol_38_540
Author(s) : Poupardin R , Reynaud S , Strode C , Ranson H , Vontas J , David JP
Ref : Insect Biochemistry & Molecular Biology , 38 :540 , 2008
Abstract : The effect of exposure of Aedes aegypti larvae to sub-lethal doses of the pyrethroid insecticide permethrin, the organophosphate temephos, the herbicide atrazine, the polycyclic aromatic hydrocarbon fluoranthene and the heavy metal copper on their subsequent tolerance to insecticides, detoxification enzyme activities and expression of detoxification genes was investigated. Bioassays revealed a moderate increase in larval tolerance to permethrin following exposure to fluoranthene and copper while larval tolerance to temephos increased moderately after exposure to atrazine, copper and permethrin. Cytochrome P450 monooxygenases activities were induced in larvae exposed to permethrin, fluoranthene and copper while glutathione S-transferase activities were induced after exposure to fluoranthene and repressed after exposure to copper. Microarray screening of the expression patterns of all detoxification genes following exposure to each xenobiotic with the Aedes Detox Chip identified multiple genes induced by xenobiotics and insecticides. Further expression studies using real-time quantitative PCR confirmed the induction of multiple CYP genes and one carboxylesterase gene by insecticides and xenobiotics. Overall, this study reveals the potential of xenobiotics found in polluted mosquito breeding sites to affect their tolerance to insecticides, possibly through the cross-induction of particular detoxification genes. Molecular mechanisms involved and impact on mosquito control strategies are discussed.
ESTHER : Poupardin_2008_Insect.Biochem.Mol.Biol_38_540
PubMedSearch : Poupardin_2008_Insect.Biochem.Mol.Biol_38_540
PubMedID: 18405832

Title : Efficacy of the pyrethroid alpha-cypermethrin against Bactrocera oleae populations from Greece, and improved diagnostic for an iAChE mutation - Margaritopoulos_2008_Pest.Manag.Sci_64_900
Author(s) : Margaritopoulos JT , Skavdis G , Kalogiannis N , Nikou D , Morou E , Skouras PJ , Tsitsipis JA , Vontas J
Ref : Pest Manag Sci , 64 :900 , 2008
Abstract : BACKGROUND: The most important pest of olive orchards worldwide is the olive fruit fly Bactrocera oleae (Gmelin). Its control in Greece has been based on organophosphates (OPs), but their intense use has led to the development of resistance. A test previously developed to monitor the trait may not be as robust as originally thought. The pyrethroid alpha-cypermethrin has recently been registered for bait sprays, as an alternative to OPs. RESULTS: The susceptibility of 20 B. oleae populations to alpha-cypermethrin was examined. Variation was observed in their response, with LD(50) ranging from 0.14 to 3.28 ng insect(-1) and resistance factors from 2.3 to 54.7. Resistance mechanisms were investigated. Cytochrome P450 monoxygenase activities showed an association with resistance. Sequences in the domain IIS4-IIS6 of the B. oleae para-type sodium channel were also analysed, but no resistance-associated mutations were identified. Finally, a novel diagnostic assay able to reliably monitor the frequency of the iAChE G488S resistance mutation was developed. CONCLUSION: This is the first attempt to evaluate the efficacy of alpha-cypermethrin against B. oleae from Greece. Data showed that it can be used effectively, but also highlighted the importance of continuous monitoring. The IIS4-IIS6 sodium channel region is the default area in which to look for resistance mutations if target-site resistance to pyrethroids arises. The application of the novel iAChE molecular diagnostic may facilitate the introduction of pyrethroids alongside OPs currently in use.
ESTHER : Margaritopoulos_2008_Pest.Manag.Sci_64_900
PubMedSearch : Margaritopoulos_2008_Pest.Manag.Sci_64_900
PubMedID: 18381673

Title : Geographical distribution and evolutionary history of organophosphate-resistant Ace alleles in the olive fly (Bactrocera oleae) - Nardi_2006_Insect.Biochem.Mol.Biol_36_593
Author(s) : Nardi F , Carapelli A , Vontas J , Dallai R , Roderick GK , Frati F
Ref : Insect Biochemistry & Molecular Biology , 36 :593 , 2006
Abstract : Acetylcholinesterase (Ace) is the molecular target of organophosphate (OP) insecticides, and two mutations that confer different levels of OP insensitivity have previously been identified in the olive fly, Bactrocera oleae. Numerous sensitive and two insensitive alleles (including one convergent acquisition) are described from the entire worldwide distribution of the fly. Most of the variation is harbored in the native range of the species and in the Middle East and consists of numerous low-frequency sensitive alleles. The insensitive alleles likely came to high frequency more recently in the Mediterranean region or in the Middle East, reaching frequencies as high as 100% in some populations, and determined a corresponding decline in overall genetic variation. We hypothesize that the major force that shaped the current distribution of resistant and non-resistant acetylcholinesterase alleles is natural selection, likely responsible for the high frequency of insensitive alleles in areas where organophosphates have been used extensively. We also discuss a role for historical contingency, that can explain why sensitive alleles are absent altogether in the species ancestral range and present in areas of recent expansion, such as California, despite the limited use of OPs.
ESTHER : Nardi_2006_Insect.Biochem.Mol.Biol_36_593
PubMedSearch : Nardi_2006_Insect.Biochem.Mol.Biol_36_593
PubMedID: 16835025
Gene_locus related to this paper: bacol-ACHE

Title : Detection of resistance-associated point mutations of organophosphate-insensitive acetylcholinesterase in the olive fruit fly, Bactrocera oleae (Gmelin) - Hawkes_2005_Pestic.Biochem.Physiol_81_154
Author(s) : Hawkes NJ , Janes W , Hemingway J , Vontas J
Ref : Pesticide Biochemistry and Physiology , 81 :154 , 2005
Abstract : We have recently identified two resistance-associated point mutations of organophosphate (OP)-insensitive acetylcholinesterase in the olive fruit fly Bactrocera oleae, the most important olive orchard pest world-wide. We have developed simple PCR-restriction fragment length polymorphism assays for each mutation utilising an AccI restriction site created by Ile214Val, and a BssHII restriction site destroyed by a neutral change always accompanying the second mutation Gly488Ser. Samples from Greece homozygous for both mutations proved the most insensitive to dimethoate. The frequencies of these mutations in field-collected samples from several countries were investigated. Ninety-three percent of samples from Greece and Albania, where OPs have been extensively used in B. oleae control, were homozygous for both mutations. Resistance-associated alleles were detected at lower frequencies, but still with both mutations in conjunction in the majority of cases, in western Mediterranean countries with limited use of OPs. Samples from South Africa, however, did not have either of the resistance-associated mutations. The double mutation haplotype clearly confers a strong selective advantage in field populations of B. oleae exposed to OPs.
ESTHER : Hawkes_2005_Pestic.Biochem.Physiol_81_154
PubMedSearch : Hawkes_2005_Pestic.Biochem.Physiol_81_154

Title : Gene expression in insecticide resistant and susceptible Anopheles gambiae strains constitutively or after insecticide exposure - Vontas_2005_Insect.Mol.Biol_14_509
Author(s) : Vontas J , Blass C , Koutsos AC , David JP , Kafatos FC , Louis C , Hemingway J , Christophides GK , Ranson H
Ref : Insect Molecular Biology , 14 :509 , 2005
Abstract : A microarray containing approximately 20 000 expressed sequence tags (ESTs; 11 760 unique EST clusters) from the malaria vector, Anopheles gambiae, was used to monitor differences in global gene expression in two insecticide resistant and one susceptible strains. Statistical analysis identified 77 ESTs that were differentially transcribed among the three strains. These include the cytochrome P450 CYP314A1, over-transcribed in the DDT resistant ZAN/U strain, and many genes that belong to families not usually associated with insecticide resistance, such as peptidases, sodium/calcium exchangers and genes implicated in lipid and carbohydrate metabolism. Short-term (6 and 10 h) effects of exposure of the pyrethroid resistant RSP strain to permethrin were also detected. Several genes belonging to enzyme families already implicated in insecticide or xenobiotic detoxification were induced, including the carboxylesterase COEAE2F gene and members of the UDP-glucuronosyl transferase and nitrilase families.
ESTHER : Vontas_2005_Insect.Mol.Biol_14_509
PubMedSearch : Vontas_2005_Insect.Mol.Biol_14_509
PubMedID: 16164607

Title : An overview of insecticide resistance - Hemingway_2002_Science_298_96
Author(s) : Hemingway J , Field L , Vontas J
Ref : Science , 298 :96 , 2002
Abstract : Insecticide resistance poses a serious threat to current malaria control efforts. The Anopheles gambiae genome will enable identification of new resistance genes and will provide new molecular targets for the design of more effective insecticides.
ESTHER : Hemingway_2002_Science_298_96
PubMedSearch : Hemingway_2002_Science_298_96
PubMedID: 12364782

Title : Resistance-associated point mutations of organophosphate insensitive acetylcholinesterase, in the olive fruit fly Bactrocera oleae - Vontas_2002_Insect.Mol.Biol_11_329
Author(s) : Vontas J , Hejazi MJ , Hawkes NJ , Cosmidis N , Loukas M , Hemingway J
Ref : Insect Molecular Biology , 11 :329 , 2002
Abstract : A 2.2-kb full length cDNA containing an ORF encoding a putative acetylcholinesterase (AChE) precursor of 673 amino acid residues was obtained by a combined degenerate PCR and RACE strategy from an organophosphate-susceptible Bactrocera oleae strain. A comparison of cDNA sequences of individual insects from susceptible and resistant strains, coupled with an enzyme inhibition assay with omethoate, indicated a novel glycine-serine substitution (G488S), at an amino acid residue which is highly conserved across species (G396 of Torpedocalifornica AChE), as a likely cause of AChE insensitivity. This mutation was also associated with a 35-40% reduction in AChE catalytic efficiency. The I199V substitution, which confers low levels of resistance in Drosophila, was also present in B. oleae (I214V) and in combination with G488S produced up to a 16-fold decrease in insecticide sensitivity. This is the first agricultural pest where resistance has been associated with an alteration in AChE, which arises from point mutations located within the active site gorge of the enzyme.
ESTHER : Vontas_2002_Insect.Mol.Biol_11_329
PubMedSearch : Vontas_2002_Insect.Mol.Biol_11_329
PubMedID: 12144698
Gene_locus related to this paper: bacol-ACHE

Title : Altered Acetylcholinesterase Confers Organophosphate Resistance in the Olive Fruit Fly Bactrocera oleae - Vontas_2001_Pestic.Biochem.Physiol_71_124
Author(s) : Vontas J , Cosmidis N , Loukas M , Tsakas S , Hejazi MJ , Ayoutanti A , Hemingway J
Ref : Pesticide Biochemistry and Physiology , 71 :124 , 2001
Abstract : An organophosphate-resistant strain of the olive fruit fly Bactrocera oleae, the most important pest for olive orchards worldwide, was obtained by laboratory selection with dimethoate. Resistance mechanisms were investigated in comparison with the colonized parental strain and a field population collected from the same area after 12 years of continuous dimethoate-based insecticide pressure. Combined biochemical and bioassay data suggested that, although esterase and/or glutathione S-transferase metabolic pathways were present and active against dimethoate, they were not selected for and did not have a major role in resistance. There was no evidence of increased oxidase activity in the resistant strains or significant synergism of dimethoate toxicity by piperonyl butoxide; thus, oxidative metabolism was not a major component of resistance. An altered acetylcholinesterase (AChE) with poorer catalytic efficiency for the substrate acetylthiocholine iodide and 5- to 16-fold lower sensitivity to inhibition by omethoate was the major resistance mechanism. Dimethoate selected the insensitive AChE allele(s) in the resistant insects, which were also insensitive to paraoxon, but the altered AChE mechanism conferred negative cross-resistance to the carbamate propoxur.
ESTHER : Vontas_2001_Pestic.Biochem.Physiol_71_124
PubMedSearch : Vontas_2001_Pestic.Biochem.Physiol_71_124