The cytochrome P450 subfamilies CYP392A and CYP392D are key players in acaricide metabolism in Tetranychusurticae.

The spider mite Tetranychus urticae is a major agricultural pest with a global distribution, extremely diverse host range and a remarkable ability to develop resistance to a wide variety of acaricides. P450 mono-oxygenases have been frequently associated with resistance development in this species. In particular enzymes of the CYP392A-subfamily were shown to metabolize a number of key acaricides, including abamectin, amitraz, fenpyroximate and the active metabolite of pyflubumide.

Insights into unique features of Drosophila CYP4G enzymes.

The cytochrome P450 enzymes of the CYP4G subfamily are some of the most intriguing insect P450s in terms of structure and function. In Drosophila, CYP4G1 is highly expressed in the oenocytes and is the last enzyme in the biosynthesis of cuticular hydrocarbons, while CYP4G15 is expressed in the brain and is of unknown function. Both proteins have a CYP4G-specific and characteristic amino acid sequence insertion corresponding to a loop between the G and H helices whose function is unclear.

Contrasting roles of cytochrome P450s in amitraz and chlorfenapyr resistance in the crop pest Tetranychus urticae.

The molecular mechanisms of amitraz and chlorfenapyr resistance remain only poorly understood for major agricultural pests and vectors of human diseases. This study focusses on a multi-resistant field strain of the crop pest Tetranychus urticae, which could be readily selected in the laboratory to high levels of amitraz and chlorfenapyr resistance. Toxicity experiments using tralopyril, the active toxophore of chlorfenapyr, suggested decreased activation as a likely mechanism underlying resistance.

Chlorfenapyr metabolism by mosquito P450s associated with pyrethroid resistance identifies potential activation markers.

Chlorfenapyr is a pro-insecticide increasingly used in combination with pyrethroids such as a-cypermethrin or deltamethrin in insecticide treated bednets (ITNs) to control malaria transmitted by pyrethroid-resistant mosquito populations. Chlorfenapyr requires P450 activation to produce tralopyril and other bioactive metabolites. Pyrethroid resistance is often associated with elevated levels of chemoprotective P450s with broad substrate specificity, which could influence chlorfenapyr activity.

Increased metabolism in combination with the novel cytochrome b target-site mutation L258F confers cross-resistance between the Q inhibitors acequinocyl and bifenazate in Tetranychus urticae.

Acequinocyl and bifenazate are potent acaricides acting at the Q site of complex III of the electron transport chain, but frequent applications of these acaricides have led to the development of resistance in spider mites. Target-site resistance caused by mutations in the conserved cd1- and ef-helices of the Q pocket of cytochrome b has been elucidated as the main resistance mechanism. We therefore monitored Q pocket mutations in European field populations of Tetranychus urticae and uncovered a new mutation, L258F.

Functional characterization of cytochrome P450s associated with pyrethroid resistance in the olive fruit fly Bactrocera oleae.

Resistance to pyrethroid insecticides has evolved in Bactrocera oleae populations in Greece, threatening the efficacy of control interventions based on this insecticide class. Here we report the collection of populations from Crete, with resistance levels reaching up to 132-folds, compared to susceptible laboratory strains and show that pyrethroid resistance is substantially suppressed by the PBO synergist, suggesting the involvement of detoxification enzymes. To identify specific candidate genes implicated in resistance, we performed comparative transcriptomic analysis, between the pyrethroid resistant populations from Crete and the susceptible laboratory strains, using both whole bodies and Malpighian tubules.

High-resolution genetic mapping reveals cis-regulatory and copy number variation in loci associated with cytochrome P450-mediated detoxification in a generalist arthropod pest.

Chemical control strategies are driving the evolution of pesticide resistance in pest populations. Understanding the genetic mechanisms of these evolutionary processes is of crucial importance to develop sustainable resistance management strategies. The acaricide pyflubumide is one of the most recently developed mitochondrial complex II inhibitors with a new mode of action that specifically targets spider mite pests.

Functional characterization of CYP6A51, a cytochrome P450 associated with pyrethroid resistance in the Mediterranean fruit fly Ceratitis capitata.

Overexpression of the cytochrome P450 monooxygenase CYP6A51 has been previously associated with pyrethroid resistance in the Mediterranean fruit fly (medfly) Ceratitis capitata, an important pest species worldwide; however, this association has not been functionally validated. We expressed CYP6A51 gene in Escherichia coli and produced a functional enzyme with preference for the chemiluminescent substrate Luciferin-ME EGE. In vitro metabolism assays revealed that CYP6A51 is capable of metabolizing two insecticides that share the same mode of action, λ-cyhalothrin and deltamethrin, whereas no metabolism or substrate depletion was observed in the presence of spinosad or malathion.

Rapid selection of a pyrethroid metabolic enzyme CYP9K1 by operational malaria control activities.

Since 2004, indoor residual spraying (IRS) and long-lasting insecticide-impregnated bednets (LLINs) have reduced the malaria parasite prevalence in children on Bioko Island, Equatorial Guinea, from 45% to 12%. After target site-based (knockdown resistance; ) pyrethroid resistance was detected in 2004 in (formerly known as the M form of the complex), the carbamate bendiocarb was introduced. Subsequent analysis showed that alone was not operationally significant, so pyrethroid-based IRS was successfully reintroduced in 2012.

Insecticide resistance in Trialeurodes vaporariorum populations and novel diagnostics for kdr mutations.

Background: Neonicotinoids, pyrethroids and ketoenols are currently used for the control of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). In this study, insecticide resistance status and mechanisms were investigated using classical bioassays and molecular techniques.

Results: Dose-response bioassays were performed on 19 Greek populations, among the 35 different whitefly populations used for the whole analysis.

A glutathione-S-transferase (TuGSTd05) associated with acaricide resistance in Tetranychus urticae directly metabolizes the complex II inhibitor cyflumetofen.

Cyflumetofen is a recently introduced acaricide with a novel mode of action, acting as an inhibitor of complex II of mitochondrial electron transport chain. It is activated by hydrolysis and the resulting de-esterified metabolite is a much stronger inhibitor. Cyflumetofen represents a great addition for the control of mite species including Tetranychus urticae, a major agricultural pest, which has the ability to develop resistance to most classes of pesticides rapidly.

Development of a lateral flow test to detect metabolic resistance in Bemisia tabaci mediated by CYP6CM1, a cytochrome P450 with broad spectrum catalytic efficiency.

Cotton whitefly, Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) is a major sucking pest in many agricultural and horticultural cropping systems globally. The frequent use of insecticides of different mode of action classes resulted in populations resisting treatments used to keep numbers under economic damage thresholds.

Molecular analysis of resistance to acaricidal spirocyclic tetronic acids in Tetranychus urticae: CYP392E10 metabolizes spirodiclofen, but not its corresponding enol.

Spirodiclofen is one of the most recently developed acaricides and belongs to the new family of spirocyclic tetronic acids (ketoenols). This new acaricidal family is an important chemical tool in resistance management strategies providing sustainable control of spider mites such as Tetranychus urticae. Spirodiclofen targets lipid biosynthesis mediated by direct inhibition of acetyl coenzyme A carboxylase (ACCase).