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A novel acetylcholinesterase gene in mosquitoes codes for the insecticide target and is non-homologous to the ace gene in Drosophila.

ABSTRACT: Acetylcholinesterase (AChE) is the target of two major insecticide families, organophosphates (OPs) and carbamates. AChE insensitivity is a frequent resistance mechanism in insects and responsible mutations in the ace gene were identified in two Diptera, Drosophila melanogaster and Musca domestica. However, for other insects, the ace gene cloned by homology with Drosophila does not code for the insensitive AChE in resistant individuals, indicating the existence of a second ace locus. We identified two AChE loci in the genome of Anopheles gambiae, one (ace-1) being a new locus and the other (ace-2) being homologous to the gene previously described in Drosophila. The gene ace-1 has no obvious homologue in the Drosophila genome and was found in 15 mosquito species investigated. In An. gambiae, ace-1 and ace-2 display 53% similarity at the amino acid level and an overall phylogeny indicates that they probably diverged before the differentiation of insects. Thus, both genes are likely to be present in the majority of insects and the absence of ace-1 in Drosophila is probably due to a secondary loss. In one mosquito (Culex pipiens), ace-1 was found to be tightly linked with insecticide resistance and probably encodes the AChE OP target. These results have important implications for the design of new insecticides, as the target AChE is thus encoded by distinct genes in different insect groups, even within the Diptera: ace-2 in at least the Drosophilidae and Muscidae and ace-1 in at least the Culicidae. Evolutionary scenarios leading to such a peculiar situation are discussed.

SUBMITTER: Weill M

PROVIDER: S-EPMC1691131 | biostudies-other | 2002 Oct

REPOSITORIES: biostudies-other

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A novel acetylcholinesterase gene in mosquitoes codes for the insecticide target and is non-homologous to the ace gene in Drosophila.

Weill Mylène M Fort Philippe P Berthomieu Arnaud A Dubois Marie Pierre MP Pasteur Nicole N Raymond Michel M

Proceedings. Biological sciences 20021001 1504

Acetylcholinesterase (AChE) is the target of two major insecticide families, organophosphates (OPs) and carbamates. AChE insensitivity is a frequent resistance mechanism in insects and responsible mutations in the ace gene were identified in two Diptera, Drosophila melanogaster and Musca domestica. However, for other insects, the ace gene cloned by homology with Drosophila does not code for the insensitive AChE in resistant individuals, indicating the existence of a second ace locus. We identifi ...[more]

PMID: 12396499

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Project description:BackgroundInsecticide resistance is a substantial problem in controlling agricultural and medical pests. Detecting target site mutations is crucial to manage insecticide resistance. Though PCR-based methods have been widely used in this field, they are time-consuming and inefficient, and typically have a high false positive rate. Acetylcholinesterases (Ace) is the neural target of the widely used organophosphate (OP) and carbamate insecticides. However, there is not any software available to detect insecticide resistance associated mutations in RNA-Seq data at present.ResultsA computational pipeline ACE was developed to detect resistance mutations of ace in insect RNA-Seq data. Known ace resistance mutations were collected and used as a reference. We constructed a Web server for ACE, and the standalone software in both Linux and Windows versions is available for download. ACE was used to analyse 971 RNA-Seq data from 136 studies in 7 insect pests. The mutation frequency of each RNA-Seq dataset was calculated. The results indicated that the resistance frequency was 30%-44% in an eastern Ugandan Anopheles population, thus suggesting this resistance-conferring mutation has reached high frequency in these mosquitoes in Uganda. Analyses of RNA-Seq data from the diamondback moth Plutella xylostella indicated that the G227A mutation was positively related with resistance levels to organophosphate or carbamate insecticides. The wasp Nasonia vitripennis had a low frequency of resistant reads (<5%), but the agricultural pests Chilo suppressalis and Bemisia tabaci had a high resistance frequency. All ace reads in the 30 B. tabaci RNA-Seq data were resistant reads, suggesting that insecticide resistance has spread to very high frequency in B. tabaci.ConclusionsTo the best of our knowledge, the ACE pipeline is the first tool to detect resistance mutations from RNA-Seq data, and it facilitates the full utilization of large-scale genetic data obtained by using next-generation sequencing.

Project description:BackgroundThe auto-dissemination approach has been shown effective at treating cryptic refugia that remain unaffected by existing mosquito control methods. This approach relies on adult mosquito behavior to spread larvicide to breeding sites at levels that are lethal to immature mosquitoes. Prior studies demonstrate that 'dissemination stations,' deployed in mosquito-infested areas, can contaminate adult mosquitoes, which subsequently deliver the larvicide to breeding sites. In some situations, however, preventative measures are needed, e.g., to mitigate seasonal population increases. Here we examine a novel approach that combines elements of autocidal and auto-dissemination strategies by releasing artificially reared, male mosquitoes that are contaminated with an insecticide.MethodologyLaboratory and field experiments examine for model-predicted impacts of pyriproxyfen (PPF) directly applied to adult male Aedes albopictus, including (1) the ability of PPF-treated males to cross-contaminate females and to (2) deliver PPF to breeding sites.Principal findingsSimilar survivorship was observed in comparisons of PPF-treated and untreated males. Males contaminated both female adults and oviposition containers in field cage tests, at levels that eliminated immature survivorship. Field trials demonstrate an ability of PPF-treated males to transmit lethal doses to introduced oviposition containers, both in the presence and absence of indigenous females. A decline in the Ae. albopictus population was observed following the introduction of PPF-treated males, which was not observed in two untreated field sites.Conclusions/significanceThe results demonstrate that, in cage and open field trials, adult male Ae. albopictus can tolerate PPF and contaminate, either directly or indirectly, adult females and immature breeding sites. The results support additional development of the proposed approach, in which male mosquitoes act as vehicles for insecticide delivery, including exploration of the approach with additional medically important mosquito species. The novelty and importance of this approach is an ability to safely achieve auto-dissemination at levels of intensity that may not be possible with an auto-dissemination approach that is based on indigenous females. Specifically, artificially-reared males can be released and sustained at any density required, so that the potential for impact is limited only by the practical logistics of mosquito rearing and release, rather than natural population densities and the self-limiting impact of an intervention upon them.

Dataset Information

A novel acetylcholinesterase gene in mosquitoes codes for the insecticide target and is non-homologous to the ace gene in Drosophila.

Publications

A novel acetylcholinesterase gene in mosquitoes codes for the insecticide target and is non-homologous to the ace gene in Drosophila.

Similar Datasets

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