Project description:Insecticide resistance is a worldwide threat for vector control around the world, and Aedes aegypti , the main vector of several arboviruses, is a particular concern. To better understand the mechanisms of resistance, four isofemale strains originally from French Guiana were isolated and analysed using combined approaches. The activity of detoxification enzymes involved in insecticide resistance was assayed, and mutations located at positions 1016 and 1534 of the sodium voltage-gated channel gene, which have been associated with pyrethroid resistance in Aedes aegypti populations in Latin America, were monitored. Resistance to other insecticide families (organophosphates and carbamates) was evaluated. A large-scale proteomic analysis was performed to identify proteins involved in insecticide resistance. Our results revealed a metabolic resistance and resistance associated with a mutation of the sodium voltage-gated channel gene at position 1016. Metabolic resistance was mediated through an increase of esterase activity in most strains but also through the shifts in the abundance of several cytochrome P450 (CYP450s). Overall, resistance to deltamethrin was linked in the isofemale strains to resistance to other class of insecticides, suggesting that cross- and multiple resistance occur through selection of mechanisms of metabolic resistance. These results give some insights into resistance to deltamethrin and into multiple resistance phenomena in populations of Ae. aegypti
Project description:This microarray study aimed at evaluating the impact of mosquito chemical environment on the selection of insecticide resistance mechanisms. Here the mosquito Aedes aegypti was used as a model to perform a laboratory experiment combining mosquito larvae exposure to a sub-lethal dose of xenobiotic and their selection with the insecticide permethrin. After ten generations, bioassays and a transcriptome profiling with the 15K microarray Aedes detox chip plus microarray were performed comparatively on all strains.
Project description:Aedes aegypti (L.) is the primary vector of many emerging arboviruses. Insecticide resistance among mosquito populations is a consequence of the application of insecticides for mosquito control. We used RNA-sequencing to compare transcriptomes between permethrin resistant and susceptible strains of Florida Ae. aegypti in response to Zika virus infection. A total of 2,459 transcripts were expressed at significantly different levels between resistant and susceptible Ae. aegypti. Gene ontology analysis placed these genes into 7 categories of biological processes. The 863 transcripts were expressed at significantly different levels between two strains (up/down regulated) more than 2-fold. Quantitative real-time PCR analysis validated Zika-infected response, and suggested a highly overexpressed P450, with AAEL014617 and AAEL006798 as potential candidates for the molecular mechanism of permethrin resistance in Ae. aegypti. Our findings indicated that most detoxification enzymes and immune system enzymes altered their gene expression between the two strains of Ae. aegypti in response to Zika virus infection. Understanding the interactions of arboviruses with resistant mosquito vectors at the molecular level allows for the possible development of new approaches in mitigating arbovirus transmission. This information sheds light on Zika-induced changes in the insecticide resistance of Ae. aegypti with implications for mosquito control strategies.
Project description:This microarray study aimed at comparing constitutive gene expression levels between an Aedes aegypti insecticide-resistant strain (Imida-R) selected at the larval stage with the neonicotinoid insecticide imidacloprid for 10 generations and the parental strain (Bora-Bora) susceptible to all insecticides. Strains comparison was performed at both larval (4th stage larvae) and adult (3 days-old adults females, non-blood fed) stages.
Project description:This study aimed at comparing gene transcription using microarrays and protein expression using 2D-DIGE between an Aedes aegypti insecticide-resistant strain (LiTOX) selected for 28 generations at the larval stage with field-collected leaf litter containing persistent Bacillus thuringiensis var. israelensis (Bti) toxins and the parental strain (Bora-Bora) susceptible to all insecticides. We focused on the tissue where the mode of action of the insecticide takes place: the midgut of the larvae.
Project description:Aedes aegypti SP strain vs. SMK strain. Aedes aegypti is the major vector of yellow fever and dengue/dengue hemorrhagic fever. Starting with a population collected from Singapore, we established a pyrethroid-resistant A. aegypti strain (SP) and investigated three major possible mechanisms of insecticide resistance. After 10 generations of adult selection, an A. aegypti strain developed 1650-fold resistance to permethrin, which is one of the most widely used pyrethroid insecticides for mosquito control. SP larvae also developed 8790-fold resistance following selection of the adults. Prior to the selections, the frequencies of V1016G and F1534C mutations in domains II and III, respectively, of voltage-sensitive sodium channel genes (Vssc) were 0.44 and 0.56, respectively. In contrast, only G1016 alleles were present after two permethrin selections, indicating that G1016 can contribute more to the insensitivity of Vssc than C1534. In vivo metabolism studies showed that the SP strain excreted permethrin metabolites more rapidly than the susceptible SMK strain. Pretreatment with piperonyl butoxide caused strong inhibition of excretion of permethrin metabolites, suggesting that cytochrome P450 monooxygenases (P450s) play an important role in resistance development. In vitro metabolism studies also indicated an association of P450s with resistance. Microarray analysis showed that multiple P450 genes were over-expressed during the larval and adult stages in the SP strain. Following quantitative real time PCR, we focused on two P450 isoforms, CYP9M6 and CYP6BB2, and confirmed that they were capable of detoxifying permethrin to 4'-HO-permethrin. Over-expression of CYP9M6 was partially due to gene amplification. Association analysis demonstrated that CYP9M6 and CYP6BB2 complementarily conferred permethrin resistance. Two other P450s (CYP9J26 and CYP9J28), which are capable of metabolizing permethrin, were also over-expressed in the SP strain, indicating that at least four P450 isoforms are likely involved in resistance development. Our data show that it is unlikely that reduced cuticle penetration of permethrin contributes to resistance. One-color experiment with two strains (SP, SMK) and 3 developmental stages/genders (larvae, adult males, and adult females), 4 biological replicates each.