Nkya et al 2014 - Insecticide resistance mechanisms associated with different environments in the malaria vector Anopheles gambiae. A case study in Tanzania
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ABSTRACT: Nine Anopheles gambiae populations were sampled in three areas of Tanzania showing contrasting agriculture activity, urbanization and usage of insecticides for vector control. Insecticide resistance levels were measured in larvae and adults through bioassays with deltamethrin, DDT and bendiocarb. A microarray approach was used for identifying transcription level variations associated to different environments and insecticide resistance. the Ifakara strain originating from central Tanzania and susceptible to all insecticides was used as a reference strain.
Project description:Modifications of metabolic pathways are important in insecticide resistance evolution. Mutations leading to changes in expression levels or substrate specificities of cytochrome P450 (P450), glutathione-S-transferase (GST) and esterase genes have been linked to many cases of resistance with the responsible enzyme being shown to utilize the insecticide as a substrate. Many studies show that the substrates of enzymes are capable of inducing the expression of those enzymes. We investigated if this was the case for insecticides and the enzymes responsible for their metabolism. The induction responses for P450s, GSTs and esterases to six different insecticides were investigated using a custom designed microarray in Drosophila melanogaster. Even though these gene families can all contribute to insecticide resistance, their induction responses by insecticides is minimal. The insecticides spinosad, diazinon, nitenpyram, lufenuron and dicyclanil did not induce any P450, GST or esterase gene expression. DDT was the only insecticide tested capable of eliciting an induction response, but only low levels for one GST and one P450. These results are in contrast to the induction responses observed for the natural plant compound caffeine and the barbituate drug phenobarbital, both of which induced a number of P450 and GST genes to high. Our results show that although insects evolve metabolic resistance to insecticides, induction does not usually have a role in survival after insecticide application, and induction studies cannot be used to predict which genes are capable of metabolizing insecticides. This has implications for managing the evolution of metabolic insecticide resistance in natural insect populations. Keywords: induction response after treatment by various compounds
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:A microarray experimental design with dye balancing was adopted to compare the gene expression profiles of the following experimental groups; Field collected Makkah and Jeddah strains unexposed to any insecticide Fully insecticide susceptible New Orleans and Rockefeller laboratory strains. Laboratory Jeddah strain (F5) without exposure to insecticides Laboratory Jeddah strains selected for deltamethrin resistance (F5). For each comparison (field, lab selected or unselected vs susceptible), three biological replicates were used. The two susceptible strains, New Orleans and Rockefeller served as reference.
Project description:Resistance to pyrethroids, the only insecticide approved for bednets, threatens control of the major malaria vector, Anopheles funestus, in Malawi. To improve the management of such resistance countrywide, it is crucial to understand the dynamics and mechanisms driving resistance in the field. In this study the levels of insecticide resistance were determined across the highly endemic densely populated lake and southern agricultural area. Insecticide resistance to pyrethoids was assessed using standardized WHO bioassay methods and resistant mosquitoes were hybridized to susceptible mosquitoes. This microarray analysis revealed the key role of cytochrome P450 genes such as CYP6P9a, CYP6P9b and CYP6M7. However, a significant shift in the over-expression of these CYP450s was detected across a south/north transect, with CYP6M7 more highly over-transcribed in the two northern collection sites and the tandemly duplicated genes, CYP6P9a and CYP6P9b, more greatly over-transcribed in the south.
Project description:Comparison of insecticide resistant mosquitoes (An. arabiensis) with control samples, comparison of resistant samples with susceptible (Dongola) strain and comparison of resistant (Sennar) strain with susceptible (Dongola) strain
Project description:Liver tissue from three-spine stickleback individuals from 3 populations were tested on arrays to determine array suitability for transcriptomics experiments.
Project description:Field resistant Anopheles coluzzii were compared to the lab susceptible Anopheles coluzzii N'Gousso. The samples were collected in 2014 in Burkina Faso and show resistance to pyrethroid insecticides.
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:Mosquitoes host and pass on to humans a variety of disease-causing pathogens such as infectious viruses and other parasitic microorganisms. The emergence and spread of insecticide resistance is threatening the effectiveness of current control measures for common mosquito vector borne diseases, such as malaria, dengue and Zika. Therefore, the emerging resistance to the widely used pyrethroid insecticides is an alarming problem for public health. Among the new approaches implemented for pest control, one of the most promising is RNA interference (RNAi). The aim of this study was to provide a feasible RNAi solution that can be applied on wild pyrethroid resistant mosquito populations in the near future. To achieve this, high dsRNA efficacy at economic quantities is required. It is recognized that the sodium channel transcript variability governs its functional diversity including the emergence of insecticide resistance. Therefore, to maximize the RNAi effect, we tiled a number of overlapping dsRNA constructs that together target about half of the voltage-gated sodium channel (VGSC) transcript variants annotated in this work. This strategy provided a refined dsRNA trigger that increased mortality with a three-fold decrease in dsRNA amounts compared to the primary VGSC dsRNA construct. Thus, we demonstrated the use of RNA interference (RNAi) to increase susceptibility of adult mosquitoes to a widely used pyrethroid insecticide. Small RNA sequences from 5 mosquitoes treated with Random or VGSC dsRNAs were generated using Illumina HiSeq 2500.