Copy Number Variation and Transposable Elements Feature in Recent, Ongoing Adaptation at the Cyp6g1 Locus

The increased transcription of the Cyp6g1 gene of Drosophila melanogaster, and consequent resistance to insecticides such as DDT, is a widely cited example of adaptation mediated by cis-regulatory change. A fragment of an Accord transposable element inserted upstream of the Cyp6g1 gene is causally associated with resistance and has spread to high frequencies in populations around the world since the 1940s. Here we report the existence of a natural allelic series at this locus of D. melanogaster, involving copy number variation of Cyp6g1, and two additional transposable element insertions (a P and an HMS-Beagle). We provide evidence that this genetic variation underpins phenotypic variation, as the more derived the allele, the greater the level of DDT resistance. Tracking the spatial and temporal patterns of allele frequency changes indicates that the multiple steps of the allelic series are adaptive. Further, a DDT association study shows that the most resistant allele, Cyp6g1-[BP], is greatly enriched in the top 5% of the phenotypic distribution and accounts for ∼16% of the underlying phenotypic variation in resistance to DDT. In contrast, copy number variation for another candidate resistance gene, Cyp12d1, is not associated with resistance. Thus the Cyp6g1 locus is a major contributor to DDT resistance in field populations, and evolution at this locus features multiple adaptive steps occurring in rapid succession

Ecologically Appropriate Xenobiotics Induce Cytochrome P450s in Apis mellifera

BACKGROUND: Honey bees are exposed to phytochemicals through the nectar, pollen and propolis consumed to sustain the colony. They may also encounter mycotoxins produced by Aspergillus fungi infesting pollen in beebread. Moreover, bees are exposed to agricultural pesticides, particularly in-hive acaricides used against the parasite Varroa destructor. They cope with these and other xenobiotics primarily through enzymatic detoxificative processes, but the regulation of detoxificative enzymes in honey bees remains largely unexplored. METHODOLOGY/PRINCIPAL FINDINGS: We used several approaches to ascertain effects of dietary toxins on bee susceptibility to synthetic and natural xenobiotics, including the acaricide tau-fluvalinate, the agricultural pesticide imidacloprid, and the naturally occurring mycotoxin aflatoxin. We administered potential inducers of cytochrome P450 enzymes, the principal biochemical system for Phase 1 detoxification in insects, to investigate how detoxification is regulated. The drug phenobarbital induces P450s in many insects, yet feeding bees with phenobarbital had no effect on the toxicity of tau-fluvalinate, a pesticide known to be detoxified by bee P450s. Similarly, no P450 induction, as measured by tau-fluvalinate tolerance, occurred in bees fed xanthotoxin, salicylic acid, or indole-3-carbinol, all of which induce P450s in other insects. Only quercetin, a common pollen and honey constituent, reduced tau-fluvalinate toxicity. In microarray comparisons no change in detoxificative gene expression was detected in phenobarbital-treated bees. However, northern blot analyses of guts of bees fed extracts of honey, pollen and propolis showed elevated expression of three CYP6AS P450 genes. Diet did not influence tau-fluvalinate or imidacloprid toxicity in bioassays; however, aflatoxin toxicity was higher in bees consuming sucrose or high-fructose corn syrup than in bees consuming honey. CONCLUSIONS/SIGNIFICANCE: These results suggest that regulation of honey bee P450s is tuned to chemicals occurring naturally in the hive environment and that, in terms of toxicological capacity, a diet of sugar is not equivalent to a diet of honey

Les mécanismes responsables de la résistance aux insecticides chez les insectes et les acariens

Insect and mite resistance mechanisms to insecticides. Insecticide resistance is documented in nearly all insects and mitesin which it has been studied. It is a major obstacle to control agriculturally important pests. Next to the already ancientknowledge on resistance this review discusses recent major breakthroughs in understanding the mechanisms, at molecularlevel, by which insects acquire resistance to natural, synthetic or bioengineered insecticides. Resistance is due either to amodification of the target affinity for the pesticide or to an increase of detoxification through some enzymatic systems. Nowthe challenge is to isolate the DNA encoding for these various proteins in order to understand what happens at the geneticlevel when an insect acquires resistance to insecticides. In this paper we review several types of resistance mechanisms(behavioural, physiological and biochemical) and we indicate the application that can be expected from this knowledge,mainly for the managing of the resistance genes in natural populations and for ecotoxicological studies

The role of malathion carboxylesterase in malathion specific resistance from Tribolium castaneum (Coleoptera: Tenebrionidae

peer reviewe

Bases moléculaires, génétiques et populationnelles de la résistance des insectes aux insecticides

National audienc

Molecular cloning of a phthalate-inducible CYP4 gene (CYP4T2) in kidney from the sea bass Dicentrarchus labrax

International audienc

Cloning of CYP4F7 a kidney-specific P450 in the sea bass Dicentrarchus labrax

International audienc

Differential sensitivity to vegetable tannins in planktonic crustacea from alpine mosquito breeding sites

International audienceThe differential capability to detoxify dietary tannins from the leaf litter of the vegetation surrounding alpine mosquito communities was experimentally investigated in different strains of planktonic crustacean taxa (Daphnia pulex, Simocephalus vetulus, and Eucypris virens) associated with the culicine populations. Tannic acid, used as an experimental standard, had differential biocidal effects in strains associated with various surrounding vegetation with different phenolic contents. Such a differential sensitivity to tannic acid was correlated with qualitative and quantitative features of cytochromes P-450, esterases, and glutathione S-transferases activities measured in these strains. This suggests that these enzymes are involved in the detoxification of vegetable tannins by these crustacean taxa. Contribution of cytochromes P-450, esterases, and glutathione S-transferases in the resistance of Crustacea to those xenobiotics was also implied by the synergistic effect in vivo of piperonyl butoxide and S,S,S, tributyl phosphorotrithioate on the toxicity of tannins. (C) 2000 Academic Press