Characterising metabolic resistance in pyrethroid-insensitive pollen beetle (Meligethes aeneus F.) from Poland and Switzerland

Proteogenomic insight into the basis of the insecticide tolerance/resistance of the pollen beetle Brassicogethes (Meligethes) aeneus

The pollen beetle is a major pest of oilseed rape. Although various resistance mechanisms have been identified, such as kdr (mutation in the sodium channel) and metabolic resistance (CYP overexpression), other "hidden" factors also exist. Some studies have stressed the importance of epistasis as a genetic background. The combination of kdr and metabolic resistance appears to be unfavorable under field conditions in the absence of pesticide selection. The regulation of detoxification enzymes can play an important role, but we highlight different detoxification markers compared to those emphasized in other studies. We also stress the importance of studying the role of markers identified as pathogenesis-related protein 5-like (PR5; upregulated by insecticides) and highlight the role of RNA (DEAD-box) helicases (downregulated by insecticides). Thus, we suggest the importance of epigenetic drivers of resistance/tolerance to pesticides. The key results are similar to those of our previous study, in which deltamethrin treatment of the pollen beetle was also investigated by a proteogenomic approach. Indeed, the mechanism leading to resistance of the pollen beetle may be an innate mechanism that the pollen beetle can also employ in natural habitats, but under field conditions (pesticide exposure), this mechanism is used to survive in response to insecticides. SIGNIFICANCE: Pesticide resistance is a serious problem that hampers the successful production of crops. Understanding the mechanisms of insecticide resistance is highly important for successful pest control, especially when considering integrated pest management. Here, using a proteogenomic approach, we identified novel markers for understanding pollen beetle resistance to pesticides. In addition, future studies will reveal the role of these markers in the multiresistance of pollen beetle populations. We highlight that the proteins identified as PR5, which are known to occur in beetles and are similar to those in plants, may be responsible for tolerance to multiple stresses. In addition, our results indicate that the RNA helicases that exhibited changes in expression may be the epigenetic drivers of multiresistance. The nature of these changes remains an open question, and their relevance in different situations (responses to different stresses) in natural habitats in the absence of pesticides can be proposed.

Indoxacarb-loaded fluorescent mesoporous silica nanoparticles for effective control of Plutella xylostella L. with decreased detoxification enzymes activities

BACKGROUND

Plutella xylostella L. is a cosmopolitan lepidopteron insect pest for numerous vegetables and crops. The extensive use of insecticides has resulted in the emergence of resistance in P. xylostella. Thus, development of innovative strategies to overcome the insecticide resistance and control P. xylostella effectively is highly desirable. Inspired by the concept and breakthrough of nanomedical strategies to treat multidrug resistance, nanotechnology may find potential application in overcoming or delaying insecticide resistance.

RESULTS

Carbon dots-embedded fluorescent mesoporous silica nanoparticles (FL-SiO₂ NPs) were successfully developed. Indoxacarb-loaded nanoparticles (IN@FL-SiO₂ NPs) were facilely prepared with loading content of 24%. The release of indoxacarb from IN@FL-SiO₂ NPs was pH sensitive. IN@FL-SiO₂ NPs exhibited better insecticidal activity against P. xylostella than indoxacarb technical under the same doses of active ingredient applied. Moreover, the activities of detoxification enzymes including GST, CarE, and P450 of P. xylostella were suppressed by treatment with IN@FL-SiO₂ NPs. Furthermore, the entry of FL-SiO₂ NPs into the midgut of P. xylostella was confirmed by CLSM observation.

CONCLUSIONS

Although there is no absolute correlation between the enzyme activity and resistance, the change in corresponding enzyme activity can afford valuable information on the resistance situation. IN@FL-SiO₂ NPs treated P. xylostella displayed higher mortality, along with decreased enzymes activities, which indicates that nano-based delivery system of insecticide could be potentially applied in insecticide resistance management. © 2020 Society of Chemical Industry.

Seven-year monitoring of pyrethroid resistance in the pollen beetle (Brassicogethes aeneus F.) during implementation of insect resistance management

BACKGROUND

An increase in the spread of pyrethroid resistance in the pollen beetle has been documented in many European countries. Pyrethroid resistance in the pollen beetle in the Czech Republic has been detected using a topical application bioassay. Resistance monitoring has been carried out during the implementation of insect resistance management.

RESULTS

The susceptibilities of nine pollen beetle populations to four pyrethroids in 2009 - 2015 in the Czech Republic are presented in this paper. The highest resistance ratio (RR) values [based on the lethal dose for 50% of the population (LD₅₀ )] obtained for deltamethrin, lambda-cyhalothrin, tau-fluvalinate and etofenprox were 500, 299, 108 and 66.9, respectively. Pollen beetle mortality after application of deltamethrin or lambda-cyhalothrin gradually decreased from 2009 to 2013. High cross-resistance between lambda-cyhalothrin and deltamethrin and low cross-resistance between lambda-cyhalothrin and etofenprox were demonstrated. A kdr mutation known to cause resistance in the pollen beetle was not detected.

CONCLUSION

A high level of resistance was recorded in most of the nine populations of the pollen beetle in 2013. In the following 2 years, a decrease in resistance associated with a population density decrease of the pollen beetle was observed in all nine populations as a result of insect resistance management based on pyrethroid reduction in winter oilseed rape. © 2017 Society of Chemical Industry.

Beyond the survival and death of the deltamethrin-threatened pollen beetle Meligethes aeneus: An in-depth proteomic study employing a transcriptome database

Insecticide resistance is an increasingly global problem that hampers pest control. We sought the mechanism responsible for survival following pyrethroid treatment and the factors connected to paralysis/death of the pollen beetle Meligethes aeneus through a proteome-level analysis using nanoLC coupled with Orbitrap Fusion™ Tribrid™ mass spectrometry. A tolerant field population of beetles was treated with deltamethrin, and the ensuing proteome changes were observed in the survivors (resistant), dead (paralyzed) and control-treated beetles. The protein database consisted of the translated transcriptome, and the resulting changes were manually annotated via BLASTP. We identified a number of high-abundance changes in which there were several dominant proteins, e.g., the electron carrier cytochrome b5, ribosomal proteins 60S RPL28, 40S RPS23 and RPS26, eIF4E-transporter, anoxia up-regulated protein, 2 isoforms of vitellogenin and pathogenesis-related protein 5. Deltamethrin detoxification was influenced by different cytochromes P450, which were likely boosted by increased cytochrome b5, but glutathione-S-transferase ε and UDP-glucuronosyltransferases also contributed. Moreover, we observed changes in proteins related to RNA interference, RNA binding and epigenetic modifications. The high changes in ribosomal proteins and associated factors suggest specific control of translation. Overall, we showed modulation of expression processes by epigenetic markers, alternative splicing and translation. Future functional studies will benefit.

BIOLOGICAL SIGNIFICANCE

Insects develop pesticide resistance, which has become one of the key issues in plant protection. This growing resistance increases the demand for pesticide applications and the development of new substances. Knowledge in the field regarding the resistance mechanism and its responses to pesticide treatment provides us the opportunity to propose a solution for this issue. Although the pollen beetle Meligethes aeneus was effectively controlled with pyrethroids for many years, there have been reports of increasing resistance. We show protein changes including production of isoforms in response to deltamethrin at the protein level. These results illustrate the insect's survival state as a resistant beetle and in its paralyzed state (evaluated as dead) relative to resistant individuals.

The use of substituted alkynyl phenoxy derivatives of piperonyl butoxide to control insecticide-resistant pests

BACKGROUND

Derivatives of piperonyl butoxide with alkynyl side chains were tested in vitro and in vivo against pyrethroid-resistant Meligethes aeneus and imidacloprid-resistant Myzus persicae.

RESULTS

Synergists with the alkynyl side chain were more effective inhibitors of P450 activity in vitro than piperonyl butoxide, and demonstrated high levels of synergism in vivo, with up to 290-fold synergism of imidacloprid against imidacloprid-resistant M. persicae.

CONCLUSIONS

These 'second-generation' synergists could overcome metabolic resistance in many pest species and possibly enable reduced rates of insecticide application in some cases. © 2016 Society of Chemical Industry.

A survey of pyrethroid-resistant populations of Meligethes aeneus F. in Poland indicates the incidence of numerous substitutions in the pyrethroid target site of voltage-sensitive sodium channels in individual beetles

The pollen beetle (Meligethes aeneus F.) is the most devastating pest of oilseed rape (Brassica napus) and is controlled by pyrethroid insecticides. However, resistance to pyrethroids in Europe is becoming widespread and predominant. Pyrethroids target the voltage-sensitive sodium channel (VSSC), and mutations in VSSC may be responsible for pyrethroid insensitivity. Here, we analysed individual beetles that were resistant to esfenvalerate, a pyrethroid, from 14 populations that were collected from oilseed rape fields in Poland. We screened the VSSC domains that were presumed to directly interact with pyrethroids. We identified 18 heterozygous nucleic acid substitutions, amongst which six caused an amino acid change: N912S, G926S, I936V, R957G, F1538L and E1553G. Our analysis of the three-dimensional structure of these domains in VSSC revealed that some of these changes may slightly influence the protein structure and hence the docking efficiency of esfenvalerate. Therefore, these mutations may impact the susceptibility of the sodium channel to the action of this insecticide.

A de novo transcriptome of European pollen beetle populations and its analysis, with special reference to insecticide action and resistance

The pollen beetle Meligethes aeneus is the most important coleopteran pest in European oilseed rape cultivation, annually infesting millions of hectares and responsible for substantial yield losses if not kept under economic damage thresholds. This species is primarily controlled with insecticides but has recently developed high levels of resistance to the pyrethroid class. The aim of the present study was to provide a transcriptomic resource to investigate mechanisms of resistance. cDNA was sequenced on both Roche (Indianapolis, IN, USA) and Illumina (LGC Genomics, Berlin, Germany) platforms, resulting in a total of ∼53 m reads which assembled into 43 396 expressed sequence tags (ESTs). Manual annotation revealed good coverage of genes encoding insecticide target sites and detoxification enzymes. A total of 77 nonredundant cytochrome P450 genes were identified. Mapping of Illumina RNAseq sequences (from susceptible and pyrethroid-resistant strains) against the reference transcriptome identified a cytochrome P450 (CYP6BQ23) as highly overexpressed in pyrethroid resistance strains. Single-nucleotide polymorphism analysis confirmed the presence of a target-site resistance mutation (L1014F) in the voltage-gated sodium channel of one resistant strain. Our results provide new insights into the important genes associated with pyrethroid resistance in M. aeneus. Furthermore, a comprehensive EST resource is provided for future studies on insecticide modes of action and resistance mechanisms in pollen beetle.

Molecular and functional characterization of CYP6BQ23, a cytochrome P450 conferring resistance to pyrethroids in European populations of pollen beetle, Meligethes aeneus

The pollen beetle (Meligethes aeneus F.) is widespread throughout much of Europe where it is a major coleopteran pest of oilseed rape (Brassica napus). The reliance on synthetic insecticides for control, particularly the pyrethroid class, has led to the development of populations with high levels of resistance. Resistance to pyrethroids is now widespread throughout Europe and is thought to be mediated by enhanced detoxification by cytochrome P450ś and/or mutation of the pyrethroid target-site, the voltage-gated sodium channel. However, in the case of cytochrome P450 mediated detoxification, the specific enzyme(s) involved has (have) not yet been identified. In this study a degenerate PCR approach was used to identify ten partial P450 gene sequences from pollen beetle. Quantitative PCR was then used to examine the level of expression of these genes in a range of pollen beetle populations that showed differing levels of resistance to pyrethroids in bioassays. The study revealed a single P450 gene, CYP6BQ23, which is significantly and highly overexpressed (up to ∼900-fold) in adults and larvae of pyrethroid resistant strains compared to susceptible strains. CYP6BQ23 overexpression is significantly correlated with both the level of resistance and with the rate of deltamethrin metabolism in microsomal preparations of these populations. Functional recombinant expression of full length CYP6BQ23 along with cytochrome P450 reductase in an insect (Sf9) cell line showed that it is able to efficiently metabolise deltamethrin to 4-hydroxy deltamethrin. Furthermore we demonstrated by detection of 4-hydroxy tau-fluvalinate using ESI-TOF MS/MS that functionally expressed CYP6BQ23 also metabolizes tau-fluvalinate. A protein model was generated and subsequent docking simulations revealed the predicted substrate-binding mode of both deltamethrin and tau-fluvalinate to CYP6BQ23. Taken together these results strongly suggest that the overexpression of CYP6BQ23 is the primary mechanism conferring pyrethroid resistance in pollen beetle populations throughout much of Europe.

RNA-sequencing analysis reveals abundant developmental stage-specific and immunity-related genes in the pollen beetle Meligethes aeneus

The pollen beetle (Meligethes aeneus) is a major pest of oilseed rape (Brassica napus) and other cruciferous crops in Europe. Pesticide-resistant pollen beetle populations are emerging, increasing the economic impact of this species. We isolated total RNA from the larval and adult stages, the latter either naïve or immunized by injection with bacteria and yeast. High-throughput RNA sequencing (RNA-Seq) was carried out to establish a comprehensive transcriptome catalogue and to screen for developmental stage-specific and immunity-related transcripts. We assembled the transcriptome de novo by combining sequence tags from all developmental stages and treatments. Gene expression data based on normalized read counts revealed several functional gene categories that were differentially expressed between larvae and adults, particularly genes associated with digestion and detoxification that were induced in larvae, and genes associated with reproduction and environmental signalling that were induced in adults. We also identified many genes associated with microbe recognition, immunity-related signalling and defence effectors, such as antimicrobial peptides (AMPs) and lysozymes. Digital gene expression analysis revealed significant differences in the profile of AMPs expressed in larvae, naïve adults and immune-challenged adults, providing insight into the steady-state differences between developmental stages and the complex transcriptional remodelling that occurs following the induction of immunity. Our data provide insight into the adaptive mechanisms used by phytophagous insects and could lead to the development of more effective control strategies for insect pests.

Preliminary studies on the susceptibility level of Ceutorchynhus assimilis (Coleoptera: Curculionidae) to acetamiprid and chlorpyrifos in Poland and resistance mechanisms of the pest to acetamiprid

The cabbage seed weevil, Ceutorchynhus assimilis (Paykull) (Coleoptera: Curculionidae) is a pest that more and more often causes large financial losses for rapeseed cultivators in Poland and other European countries. One of the reasons of these problems is the resistance of the pest to certain active substances of insecticides. The aim of the study was to assess the susceptibility level of the pest to chlorpyrifos, an organophosphate substance, and acetamiprid, a neonicotinoid, and to determine its enzymatic mechanisms of susceptibility to acetamiprid using synergists, i.e., blockers of particular enzyme groups. The presented research is the first to discuss the mechanisms of the resistance of the cabbage seed weevil to acetamiprid. The achieved results showed medium, high, or very high resistance of the cabbage seed weevil to acetamiprid and its lack of resistance to chlorpyrifos. The research on the mechanisms of the resistance of the pest to acetamiprid revealed the participation of hydrolytic enzymes blocked by S,S,S-tributylphosphorotrithioate and glutathione transferases blocked by diethyl malonate in the metabolism of acetamiprid. The results did not show the participation of oxidative enzymes and esterases blocked by piperonyl butoxide in the detoxification of acetamiprid.

The effect of a piperonyl butoxide/tau-fluvalinate mixture on pollen beetle (Meligethes aeneus) and honey bees (Apis mellifera)

BACKGROUND

Previous work has characterised pyrethroid resistance in pollen beetle (Meligethes aeneus F.) as principally an oxidative mechanism. Piperonyl butoxide (PBO) can synergise this resistance in the field, but its effects on the honey bee are thought to be unacceptable.

RESULTS

A field trial in Poland was conducted to show that a mixture of PBO and tau-fluvalinate at the registered rate gave increased and longer-lasting control of resistant pollen beetle. Four days after spraying with tau-fluvalinate, only 20% of pollen beetles were controlled, compared with 70% if the tau-fluvalinate/PBO mixture was used. No detriment to honey bee health was observed using the same mixture.

CONCLUSIONS

PBO, if used in conjunction with a pyrethroid of relatively low bee toxicity, can successfully overcome pyrethroid resistance in pollen beetle without incurring an increased loss of honey bees, even if they are present at the time of spraying.

Overexpression of a cytochrome P450 monooxygenase, CYP6ER1, is associated with resistance to imidacloprid in the brown planthopper, Nilaparvata lugens

The brown planthopper, Nilaparvata lugens, is an economically significant pest of rice throughout Asia and has evolved resistance to many insecticides including the neonicotinoid imidacloprid. The resistance of field populations of N. lugens to imidacloprid has been attributed to enhanced detoxification by cytochrome P450 monooxygenases (P450s), although, to date, the causative P450(s) has (have) not been identified. In the present study, biochemical assays using the model substrate 7-ethoxycoumarin showed enhanced P450 activity in several resistant N. lugens field strains when compared with a susceptible reference strain. Thirty three cDNA sequences encoding tentative unique P450s were identified from two recent sequencing projects and by degenerate PCR. The mRNA expression level of 32 of these was examined in susceptible, moderately resistant and highly resistant N. lugens strains using quantitative real-time PCR. A single P450 gene (CYP6ER1) was highly overexpressed in all resistant strains (up to 40-fold) and the level of expression observed in the different N. lugens strains was significantly correlated with the resistance phenotype. These results provide strong evidence for a role of CYP6ER1 in the resistance of N. lugens to imidacloprid.