Stéphane Reynaud

Université Grenoble Alpes

Background There are several indications that pesticides used in agriculture contribute to the emergence and spread of resistance of mosquitoes to vector control insecticides. However, the impact of such an indirect selection pressure has rarely been quantified and the molecular mechanisms involved are still poorly characterized. In this context, e...

Background The widespread use of pyrethroid insecticides in Africa has led to the development of strong resistance in Anopheles mosquitoes. Introducing new active ingredients can contribute to overcome this phenomenon and ensure the effectiveness of vector control strategies. Transfluthrin is a polyfluorinated pyrethroid whose structural conformati...

Background The widespread use of pyrethroid insecticides in Africa has led to the development of strong resistance in Anopheles mosquitoes. Introducing new active ingredients can contribute to overcome this phenomenon and ensure the effectiveness of vector control strategies. Transfluthrin is a polyfluorinated pyrethroid whose structural conformati...

Context: There are several indications that pesticides used in agriculture contribute to the emergence and spread of resistance of mosquitoes to vector control insecticides. However, the impact of such indirect selection pressure has rarely been quantified and the molecular mechanisms involved are still poorly characterised. In this context, experi...

A pre-diabetes syndrome induced by endocrine disruptors (ED) was recently demonstrated in the model amphibian Silurana (Xenopus) tropicalis and was suggested to be a potential cause of amphibian population decline. However, such effects have not been found in wild type frogs exposed to ED and the capacity of amphibians to physiologically develop di...

The heavy use of pesticides in agricultural areas often leads to the contamination of nearby mosquito larvae breeding sites. Exposure to complex mixtures of agrochemicals can affect the insecticide sensitivity of mosquito larvae. Our study objective was to determine whether agrochemical residues in Anopheline larval breeding sites can affect the to...

Animals must partition limited resources between their own growth and subsequent reproduction. Endocrine disruptors (ED) may cause maternal metabolic disorders that decrease successful reproduction and might be responsible for multi- and transgenerational effects in amphibians. We found that the frog Silurana (Xenopus) tropicalis, exposed to enviro...

The introduction of neonicotinoids for managing insecticide resistance in mosquitoes is of high interest as they interact with a biochemical target not previously used in public health. In this concern, Bayer developed a combination of the neonicotinoid clothianidin and the pyrethroid deltamethrin (brand name Fludora Fusion) as a new vector control...

A wide range of chemicals have been identified as endocrine disrupting chemicals (EDCs) in vertebrate species. Most studies of EDCs have focused on exposure of both male and female adults to these chemicals; however, there is clear evidence that EDCs have dramatic effects when mature or developing gametes are exposed, and consequently are associate...

Endocrine disrupting chemicals (EDCs) are ubiquitous in the environment and involve diverse chemical-receptor interactions that can perturb hormone signaling. The Organization for Economic Co-operation and Development has validated several EDC-receptor bioassays to detect endocrine active chemicals and has established guidelines for regulatory test...

Background: The introduction of neonicotinoids for managing insecticide resistance in mosquitoes is of high interest as they interact with a biochemical target not previously used in public health. In this concern, Bayer developed a combination of the neonicotinoid clothianidin and the pyrethroid deltamethrin (brand name Fludora Fusion) as a new ve...

Resistance to chemical insecticides including pyrethroids, the main insecticide class used against mosquitoes, led to a regain of interest for neonicotinoids. In this context, the present study aims at characterizing the molecular basis of neonicotinoid resistance in the mosquito Aedes aegypti. Resistance mechanisms were studied by combining transc...

Metabolic disorders induced by endocrine disruptors (ED) may contribute to amphibian population declines but no transgenerational studies have evaluated this hypothesis. Here we show that Xenopus tropicalis, exposed from the tadpole stage, to the ED benzo[a]pyrene (BaP, 50 ng.L⁻¹) produced F2 progeny with delayed metamorphosis and sexual maturity....

Concern over global amphibian declines and possible links to agrochemical use has led to research on the endocrine disrupting actions of agrochemicals, such as fertilizers, fungicides, insecticides, acaricides, herbicides, metals, and mixtures. Amphibians, like other species, have to partition resources for body maintenance, growth, and reproductio...

In addition to combating vector‐borne diseases, studying the adaptation of mosquitoes to insecticides provides a remarkable example of evolution‐in‐action driving the selection of complex phenotypes. Actually, most resistant mosquito populations show multi‐resistance phenotypes as a consequence of the variety of insecticides employed and of the com...

Numerous studies suggest that amphibians are highly sensitive to endocrine disruptors (ED) but their precise role in population decline remains unknown. This study shows that frogs exposed to a mixture of ED throughout their life cycle, at environmentally relevant concentrations, developed an unexpected metabolic syndrome. Female Silurana (Xenopus)...

In addition to combating vector-borne diseases, studying the adaptation of mosquitoes to insecticides provides a remarkable example of evolution-in-action driving the selection of complex phenotypes. Indeed, most resistant mosquito populations show multi-resistance phenotypes as a consequence of the variety of insecticides employed and of the compl...

The anti-inflammatory ibuprofen is an ubiquitous surface water contaminant. However, chronic impact of this pharmaceutical on aquatic invertebrate populations remains poorly known. In the model insect Aedes aegypti, we investigated the intergenerational consequences of parental chronic exposure to an environmentally relevant concentration of ibupro...

Significance By performing a controlled exposure of an amphibian model to endocrine disruptors (EDs) at concentrations within the range of safe drinking water, we provide evidence of the role played by these widespread contaminants in amphibian population decline through metabolic disruption. In frogs exposed throughout their life cycle, this disru...

Background The capacity of Aedes mosquitoes to resist chemical insecticides threatens the control of major arbovirus diseases worldwide. Until alternative control tools are widely deployed, monitoring insecticide resistance levels and identifying resistance mechanisms in field mosquito populations is crucial for implementing appropriate management...

Detoxification genes targeted by DNA-seq analysis of upstream regions. (XLSX)

Variations detected upstream of detoxification genes over-transcribed in resistant populations. (XLSX)

Upstream variations associated with the over transcription of detoxification genes in resistant populations. (XLSX)

Differential SNPs detected by RNA-seq. (XLSX)

Detoxification genes showing a positive correlation between their expression level and CNV. Correlations were tested for each overexpressed detoxification gene by comparing Log2 CNV versus Log2 expression ratios. Correlations with Pearson’s r ≥ 0.7 and p ≤ 0.05 were considered significant. CNV data were extracted from [28]. (TIF)

Promoter variations associated with the over-expression of detoxification genes in resistant populations. Only variations located within a 1 kb upstream of detoxification genes overexpressed in resistant populations were considered. Among them, variations showing a significant correlation (Pearson’s r ≥ 0.7 and p ≤ 0.05) between their allele freque...

Transcription data of all differentially expressed genes. (XLSX)

Correlation between allele frequencies estimated by RNA-seq and DNA-seq. Only SNPs affecting detoxification genes and detected by both approaches are shown. (TIF)

Despite numerous studies suggesting that amphibians are highly sensitive to cumulative anthropogenic stresses, the role played by endocrine disruptors (EDs) in the decline of amphibian populations remains unclear. EDs have been extensively studied in adult amphibians for their capacity to disturb reproduction by interfering with the sexual hormone...

Hazard assessment of chemical contaminants often relies on short term or partial life-cycle ecotoxicological tests, while the impact of low dose throughout the entire life cycle of species across multiple generations has been neglected. This study aimed at identifying the individual and population-level consequences of chronic water contamination b...

The capacity of mosquitoes to resist insecticides threatens the control of diseases such as dengue and malaria. Until alternative control tools are implemented, characterizing resistance mechanisms is crucial for managing resistance in natural populations. Insecticide biodegradation by detoxification enzymes is a common resistance mechanism; howeve...

Worldwide evolution of mosquito resistance to chemical insecticides represents a major challenge for public health, and the future of vector control largely relies on the development of biological insecticides that can be used in combination with chemicals (integrated management), with the expectation that populations already resistant to chemicals...

GO terms over-represented in genes differentially expressed as compared to the parental susceptible strain

Blast2GO analysis of all predicted peptides annotated as ‘conserved hypothetical protein’ or ‘hypothetical protein’ in Vectorbase against the protein database Swissprot (Blastp, E-value < 10-3, annotation cut-off = 55, GO weight = 5).

Results of cross resistance bioassays showing the number of dead larvae per pool of 20 larvae (18 replicates per strain and per insecticide; bars are for standard errors). Bioassays have been performed on 20 third instar larvae in 50mL tap water (WHO protocol), using a diagnotic dose for each insecticide killing half of the susceptible reference st...

Characteristics of the selected strains

RPKM correlations between cDNA library replicates. Each dot represents one transcript. Only transcripts showing more than 0.5 RPKM are shown.

List of genes with differential SNPs between LiTOX_N and LiTOX_S; non-synonymous changes are indicated.

Genes significantly differentially expressed in at least one selected strain (log2 fold ratio indicated when FDR≤0.01; ns: FDR>0.01; -Inf: no read detected in the selected strain)

List of supercontigs and genes affected by differential SNPs and their effects. The total number of SNPs affecting these genes is also shown.

GO terms enrichment analysis. Analysis was performed on transcripts significantly differentially expressed in each LiTOX phenotype as compared to the susceptible strain. GO terms associated with each transcript were extracted from Vectorbase. GO terms showing adjusted P values <0.05 were considered significantly enriched.

List of genes differently expressed between resistant and susceptible Bora-Bora strains classified according to their category.

Sequencing and mapping statistics.

Background: Despite the intensive use of Bacillus thuringiensis israelensis (Bti) toxins for mosquito control, little is known about the long term effect of exposure to this cocktail of toxins on target mosquito populations. In contrast to the many cases of resistance to Bacillus thuringiensis Cry toxins observed in other insects, there is no evid...

Background Despite numerous studies suggesting that amphibians are highly sensitive to cumulative anthropogenic stresses, the role pollutants play in the decline of amphibian populations remains unclear. Amongst the most common aquatic contaminants, polycyclic aromatic hydrocarbons (PAHs) have been shown to induce several adverse effects on amphibi...

Organochlorine pesticides (OCPs) are widespread environmental pollutants; two of them are highly persistent: lindane (γHCH) and chlordecone (CLD). Maize plants cope with high levels of OCP-environmental pollution, however little is known about cellular mechanisms involved in plant response to such OCP-exposures. This research was aimed at understan...

Mosquito control programmes using chemical insecticides are increasingly threatened by the development of resistance. Such resistance can be the consequence of changes in proteins targeted by insecticides (target site mediated resistance), increased insecticide biodegradation (metabolic resistance), altered transport, sequestration or other mechani...

The resistance of mosquitoes to chemical insecticides is threatening vector control programmes worldwide. Cytochrome P450 monooxygenases (CYPs) are known to play a major role in insecticide resistance allowing resistant insects to metabolize insecticides at a higher rate. Among them, members of the mosquito CYP6Z subfamily like Aedes aegypti CYP6Z8...

Bacillus thuringiensis subsp. israelensis is a bioinsecticide increasingly used worldwide for mosquito control. Despite its apparent low level of persistence in the field due to the rapid loss of its insecticidal activity, an increasing number of studies suggested that the recycling of B. thuringiensis subsp. israelensis can occur under specific, u...

Fate of Bti in the field: from the unknown to the unexpected

Mosquitoes are vectors of several major human diseases and their control is mainly based on the use of chemical insecticides. Resistance of mosquitoes to organochlorines, organophosphates, carbamates and pyrethroids led to a regain of interest for the use of neonicotinoid insecticides in vector control. The present study investigated the molecular...

Bacillus thuringiensis subsp. israelensis is a bacterium producing crystals containing Cry and Cyt proteins, which are toxic for mosquito larvae. Nothing is known about the interaction between crystal toxins and decaying leaf litter, which is a major component of several mosquito breeding sites and represents an important food source. In the presen...

Dengue is an important mosquito borne viral disease in Martinique Island (French West Indies). The viruses responsible for dengue are transmitted by Aedes aegypti, an indoor day-biting mosquito. The most effective proven method for disease prevention has been by vector control by various chemical or biological means. Unfortunately insecticide resis...

Variables used for PCA analyses. (XLS)

Detailed PCA analysis. (XLS)

The control of mosquitoes transmitting infectious diseases relies mainly on the use of chemical insecticides. However, the emergence of insecticide resistance threatens mosquito control programs. Until now, most research efforts have been focused on elucidating resistance mechanisms caused by insecticide treatments. Less attention has been paid to...

A general consensus that an increased logK(ow) led to an increase in xenobiotic uptake and bioaccumulation is accepted. In this study we compared the toxicokinetics of two chemically different xenobiotics, i.e. benzo[a]pyrene and fipronil in female green frogs. Surprisingly, the uptake rates and the bioconcentration factors (BCF) of the two contami...

Immunoglobulin (Ig) genes naturally acquire frequent premature termination codons during the error-prone V(D)J recombination process. Although B cell differentiation is linked to the expression of productive Ig alleles, the transcriptional status of nonfunctionally recombined alleles remains unclear. Here, we tracked transcription and posttranscrip...

Background: The yellow fever mosquito Aedes aegypti is a major vector of dengue and hemorrhagic fevers, causing up to 100 million dengue infections every year. As there is still no medicine and efficient vaccine available, vector control largely based on insecticide treatments remains the only method to reduce dengue virus transmission. Unfortunate...

The control of mosquitoes transmitting infectious diseases relies mainly on the use of chemical insecticides. However, resistance to most chemical insecticides threatens mosquito control programs. In this context, the spraying of toxins produced by the bacteria Bacillus thuringiensis subsp. israelensis (Bti) in larval habitats represents an alterna...

Method of extracting toxins Cry4Aa, Cry4Ba, Cry11Aa and Cyt1Aa of Bacillus thuringiensis var. israelensis from vegetable matter comprising the grinding of the vegetable matter, the addition of an extraction buffer, the sonication of the vegetable matter, the incubation of the vegetable matter and the recovery of the supernatant comprising the toxin...

Aclonifen is a diphenylether herbicide in which one ring is unsubstituted and the other is NH2-1, Cl-2, NO2-6 substituted. This substitution, especially NH2-1, is a particular feature in the diphenylether herbicidal family. In contrast with other herbicides of the same family (acifluorfen, oxyfluorfen, bifenox) this compound is not only acting thro...

Aclonifen is a diphenylether herbicide in which one ring is unsubstituted and the other is NH 2-1, Cl-2, NO 2-6 substituted. This substitution, especially NH 2-1, is a particular feature in the diphenylether herbi-cidal family. In contrast with other herbicides of the same family (acifluorfen, oxyfluorfen, bifenox) this compound is not only acting...