Project description:In the current study we examined the speed of resistance development in the silverleaf whitefly, Bemisia tabaci, after selection with either a neonicotinoid (thiacloprid) or pyrethroid (alpha-cypermethrin) insecticide alone or in combination with PBO. We used one control sample with no selection, 2 samples for neonicotinoid (thiacloprid) and Pyrethroid treatment and 2 samples for neonicotinoid (thiacloprid) + PBO and Pyrethroid + PBO treatments. The findings of this study demonstrate that PBO used in combination with certain insecticides can suppress the development of resistance in a laboratory setting.
Project description:Neonicotinoid insecticides control crop pests based on their action as agonists at the insect nicotinic acetylcholine receptor which accepts chloropyridinyl- and chlorothiazolyl- analogs almost equally well. In some cases, these compounds have also been reported to enhance plant vigor and (a)biotic stress tolerance, independent of their insecticidal function. However, this mode of action has not been specifically defined. Using Arabidopsis thaliana, we show that the neonicotinoid compounds, imidacloprid (IMI) and clothianidin (CLO), via their 6-chloropyridinyl-3-carboxylic acid and 2-chlorothiazolyl-5-carboxylic acid metabolites, respectively, induce salicylic acid (SA) – associated plant responses. SA is a phytohormone best known for its role in plant defense against pathogens and as an inducer of systemic acquired resistance; however, it can also modulate abiotic stress responses. These neonicotinoids effect a similar global transcriptional response to that of SA including genes involved in (a)biotic stress response. Furthermore, similar to SA, IMI and CLO induce systemic acquired resistance resulting in reduced growth of a powdery mildew pathogen. The action of CLO induces the endogenous synthesis of SA via the SA biosynthetic enzyme ICS1, with ICS1 required for CLO-induced accumulation of SA, expression of the SA marker PR1, and fully enhanced resistance to powdery mildew. In contrast, the action of IMI does not induce endogenous synthesis of SA. Instead, IMI is further bioactivated to 6-chloro-2-hydroxypyridinyl-3-carboxylic acid, which is shown here to be a potent inducer of PR1 and inhibitor of SA-sensitive enzymes. Thus, via different mechanisms, these chloropyridinyl- and chlorothiazolyl- neonicotinoids induce SA responses associated with enhanced stress tolerance. response to neonicotinoid insecticides
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:Neonicotinoid insecticides have been implicated in honey bee declines, with many studies showing that sub-lethal exposure impacts bee behaviors such as foraging, learning and memory. Despite the large number of ecotoxicological studies carried out to date, most focus on a handful of worker phenotypes leading to a ‘streetlight effect’ where the a priori choice of phenotypes to measure may influence the results and conclusions arising from the studies. This bias can be overcome with the use of toxicological transcriptomics, where changes in gene expression can provide a more objective view of how pesticides alter animal physiology. Here, we used RNA sequencing to examine the changes in neurogenomic states of nurse and forager honey bees that were naturally exposed to neonicotinoids in the field and artificially exposed to neonicotinoid in a controlled experiment.