A novel acetylcholinesterase gene in mosquitoes codes for the insecticide target and is non–homologous to theacegeneDrosophila

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.

Genomic Analysis of Adaptive Differentiation inDrosophila melanogaster

“…These data, and the fact that many other significant genes are involved in synaptic transmission, lead to a significant overrepresentation of a suite of synapse-related GO terms. The known examples of insecticide resistance alleles associated with acetylcholine metabolism in flies and mosquitoes (Fournier et al 1989;Weill et al 2002Weill et al , 2003 and the aforementioned significant Cyp6g1, which is also implicated in insecticide resistance (Chung et al 2007;Daborn et al 2007), suggest that selection pressures associated with insecticide or other environmental toxins vary with latitude.…”

Untitled

“…Revista Bio Ciencias 4(6), Article ID 04.06.01 December 2017 presentes en A. gambiae (Weill et al, 2002;Fournier, 2005), sin embargo, en D. melanogaster la AChE es codificada úni-camente por ace2 (Fournier et al, 1993;Weill et al, 2002;Huchard et al, 2006); estudios en otros insectos que poseen ambos genes, sugieren que ace1 es el gen responsable de una mayor actividad de la AChE (Revuelta et al, 2009;Revuelta et al, 2011).…”

Molecular cloning and characterization of the complete acetylcholinesterase gene (Ace1) from the mosquito Aedes aegypti with implications for comparative genome analysis

“…Insensitive AChE-mediated resistance due to nonsynonymous substitutions in the Ace1 gene has since been documented in a number of insects, including the mosquitoes Anopheles gambiae and Cx. pipiens (Alout et al, 2007;Weill et al, 2002Weill et al, , 2003, Anopheles albimanus (Weill et al, 2004a), and Cx. tritaeniorhynchus (Nabeshima et al, 2004).…”