Acetylcholinesterase alterations reveal the fitness cost of mutations conferring insecticide resistance

Ming Shi,Zhen Tang,Carole Alies,Andrée Lougarre,Jure Stojan,Isabelle Frémaux,Didier Fournier

doi:10.1186/1471-2148-4-5

Abstract

BackgroundInsecticide resistance is now common in insects due to the frequent use of chemicals to control them, which provides a useful tool to study the adaptation of eukaryotic genome to new environments. Although numerous potential mutations may provide high level of resistance, only few alleles are found in insect natural populations. Then, we hypothesized that only alleles linked to the highest fitness in the absence of insecticide are selected.ResultsTo obtain information on the origin of the fitness of resistant alleles, we studied Drosophila melanogaster acetylcholinesterase, the target of organophosphate and carbamate insecticides. We produced in vitro 15 possible proteins resulting from the combination of the four most frequent mutations and we tested their catalytic activity and enzymatic stability. Mutations affected deacetylation of the enzyme, decreasing or increasing its catalytic efficiency and all mutations diminished the stability of the enzyme. Combination of mutations result to an additive alteration.ConclusionOur findings suggest that the alteration of activity and stability of acetylcholinesterase are at the origin of the fitness cost associated with mutations providing resistance. Magnitude of the alterations was related to the allelic frequency in Drosophila populations suggesting that the fitness cost is the main driving force for the maintenance of resistant alleles in insecticide free conditions.

Highlights

Insecticide resistance is common in insects due to the frequent use of chemicals to control them, which provides a useful tool to study the adaptation of eukaryotic genome to new environments
Insecticide resistance offers the opportunity to study the adaptation of eukaryotes to variable environments
Resistance can be defined as the adaptation of a population from an environment free of insecticide to a new environment contaminated with new toxic molecules

Summary

Introduction

Insecticide resistance is common in insects due to the frequent use of chemicals to control them, which provides a useful tool to study the adaptation of eukaryotic genome to new environments. Numerous potential mutations may provide high level of resistance, only few alleles are found in insect natural populations. Since the 1940's, the entire planet has been spread with insecticides and a lot of insects have developed resistance. Insecticide resistance offers the opportunity to study the adaptation of eukaryotes to variable environments. Resistance can be defined as the adaptation of a population from an environment free of insecticide to a new environment contaminated with new toxic molecules. Three main mechanisms of resistance to insecticides occur: reduction of insecticide penetration, increased degradation and modification of the insecticide target. It is a key enzyme in the cholinergic synapses where it rapidly terminates nerve impulses by catalyzing (page number not for citation purposes)

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Results

Conclusion