Identification of proteins associated with pyrethroid resistance by iTRAQ-based quantitative proteomic analysis in Culex pipiens pallens

Comparative Proteomics of Resistant and Susceptible Strains of Frankliniella occidentalis to Abamectin

Western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae) is an invasive agricultural pest with developed resistance to abamectin in some strains due to frequent treatment with the pesticide. In this study, we examined differentially expressed proteins (DEPs) between abamectin-resistant (AbaR; under abamectin selective pressure) and susceptible strains (AbaS; without abamectin selective pressure) of F. occidentalis. Proteins were isolated from second instar larvae of both strains and separated via two-dimensional polyacrylamide gel electrophoresis. Nano-flow liquid chromatography-tandem mass spectrometry identified selected protein spot features. From 70 DEPs, 43 spot features were identified: A total of 23 showed an increase in abundance, and 20 were down-regulated in response to abamectin pressure. The enzymatic and structural proteins were classified into the functional groups of macromolecular metabolisms, signaling and cellular processes, immune system, genetic information processing, and exoskeleton-related proteins. The up-regulation of exoskeleton-related proteins may contribute to forming a thicker cuticle, potentially hindering abamectin penetration, which is an interesting finding that needs further investigation. Two novel proteins, triacylglycerol lipase and cuticle protein CPF 2, were only expressed in AbaR. This work provides insights into abamectin resistance mechanisms in F. occidentalis, which will provide important information for developing insecticide resistance management approaches for this pest.

Quantitative proteomics analysis of permethrin and temephos-resistant Ae. aegypti revealed diverse differentially expressed proteins associated with insecticide resistance from Penang Island, Malaysia

Synthetic insecticides are the primary vector control method used globally. However, the widespread use of insecticides is a major cause of insecticide-resistance in mosquitoes. Hence, this study aimed at elucidating permethrin and temephos-resistant protein expression profiles in Ae. aegypti using quantitative proteomics. In this study, we evaluated the susceptibility of Ae. aegypti from Penang Island dengue hotspot and non-hotspot against 0.75% permethrin and 31.25 mg/l temephos using WHO bioassay method. Protein extracts from the mosquitoes were then analysed using LC-ESI-MS/MS for protein identification and quantification via label-free quantitative proteomics (LFQ). Next, Perseus 1.6.14.0 statistical software was used to perform differential protein expression analysis using ANOVA and Student's t-test. The t-test selected proteins with≥2.0-fold change (FC) and ≥2 unique peptides for gene expression validation via qPCR. Finally, STRING software was used for functional ontology enrichment and protein-protein interactions (PPI). The WHO bioassay showed resistance with 28% and 53% mortalities in adult mosquitoes exposed to permethrin from the hotspot and non-hotspot areas. Meanwhile, the susceptibility of Ae. aegypti larvae revealed high resistance to temephos in hotspot and non-hotspot regions with 80% and 91% mortalities. The LFQ analyses revealed 501 and 557 (q-value <0.05) differentially expressed proteins in adults and larvae Ae. aegypti. The t-test showed 114 upregulated and 74 downregulated proteins in adult resistant versus laboratory strains exposed to permethrin. Meanwhile, 13 upregulated and 105 downregulated proteins were observed in larvae resistant versus laboratory strains exposed to temephos. The t-test revealed the upregulation of sodium/potassium-dependent ATPase β2 in adult permethrin resistant strain, H15 domain-containing protein, 60S ribosomal protein, and PB protein in larvae temephos resistant strain. The downregulation of troponin I, enolase phosphatase E1, glucosidase 2β was observed in adult permethrin resistant strain and tubulin β chain in larvae temephos resistant strain. Furthermore, the gene expression by qPCR revealed similar gene expression patterns in the above eight differentially expressed proteins. The PPI of differentially expressed proteins showed a p-value at <1.0 x 10-16 in permethrin and temephos resistant Ae. aegypti. Significantly enriched pathways in differentially expressed proteins revealed metabolic pathways, oxidative phosphorylation, carbon metabolism, biosynthesis of amino acids, glycolysis, and citrate cycle. In conclusion, this study has shown differentially expressed proteins and highlighted upregulated and downregulated proteins associated with insecticide resistance in Ae. aegypti. The validated differentially expressed proteins merit further investigation as a potential protein marker to monitor and predict insecticide resistance in field Ae. aegypti. The LC-MS/MS data were submitted into the MASSIVE database with identifier no: MSV000089259.

A chromosome-level genome assembly of Stenchaetothrips biformis and comparative genomic analysis highlights distinct host adaptations among thrips

Insects have a limited host range due to genomic adaptation. Thysanoptera, commonly known as thrips, occupies distinct feeding habitats, but there is a lack of comparative genomic analyses and limited genomic resources available. In this study, the chromosome-level genome of Stenchaetothrips biformis, an oligophagous pest of rice, is assembled using multiple sequencing technologies, including PacBio, Illumina short-reads, and Hi-C technology. A 338.86 Mb genome is obtained, consisting of 1269 contigs with a contig N50 size of 381 kb and a scaffold N50 size of 18.21 Mb. Thereafter, 17,167 protein-coding genes and 36.25% repetitive elements are annotated. Comparative genomic analyses with two other polyphagous thrips, revealing contracted chemosensory-related and expanded stress response and detoxification gene families in S. biformis, potentially facilitating rice adaptation. In the polyphagous thrips species Frankliniella occidentalis and Thrips palmi, expanded gene families are enriched in metabolism of aromatic and anthocyanin-containing compounds, immunity against viruses, and detoxification enzymes. These expansion gene families play crucial roles not only in adapting to hosts but also in development of pesticide resistance, as evidenced by transcriptome results after insecticides treatment. This study provides a chromosome-level genome assembly and lays the foundation for further studies on thrips evolution and pest management.

Insights into the Effects of Insecticides on Aphids (Hemiptera: Aphididae): Resistance Mechanisms and Molecular Basis

With the passage of time and indiscreet usage of insecticides on crops, aphids are becoming resistant to their effect. The different classes of insecticides, including organophosphates, carbamates, pyrethroids and neonicotinoids, have varied effects on insects. Furthermore, the molecular effects of these insecticides in aphids, including effects on the enzymatic machinery and gene mutation, are resulting in aphid resistance to the insecticides. In this review, we will discuss how aphids are affected by the overuse of pesticides, how resistance appears, and which mechanisms participate in the resistance mechanisms in various aphid species as significant crop pests. Gene expression studies were analyzed using the RNA-Seq technique. The stress-responsive genes were analyzed, and their expression in response to insecticide administration was determined. Putative insecticide resistance-related genes, cytochrome P450, glutathione S-transferase, carboxylesterase CarEs, ABC transporters, cuticle protein genes, and trypsin-related genes were studied. The review concluded that if insecticide-susceptible aphids interact with ample dosages of insecticides with sublethal effects, this will result in the upregulation of genes whose primary role is to detoxify insecticides. In the past decade, certain advancements have been observed regarding insecticide resistance on a molecular basis. Even so, not much is known about how aphids detoxify the insecticides at molecular level. Thus, to attain equilibrium, it is important to observe the manipulation of pest and insect species with the aim of restoring susceptibility to insecticides. For this purpose, this review has included critical insights into insecticide resistance in aphids.

New insights into cypermethrin insecticide resistance mechanisms of Culex pipiens pallens by proteome analysis

BACKGROUND

Due to the development of insecticide resistance in mosquitoes, with worldwide mosquito-borne diseases resurgence in recent years, recent advances in proteome technology have facilitated a proteome-wide analysis of insecticide resistance-associated proteins in mosquitoes. Understanding the complexity of the molecular basis of insecticide resistance mechanisms employed by mosquitoes will help in designing the most effective and sustainable mosquito control methods.

RESULTS

After 30 generations, insecticide-selected strains showed elevated resistance levels to the cypermethrin used for selection. Proteome data allowed the detection of 2892 proteins, of which 2885 differentially expressed proteins (DEPs) achieved quantitative significances in four stages (egg, larvae, pupae, adult) of Culex pipiens pallens cypermethrin-resistant strain as compared to the susceptible strain. Among them, a significant enrichment of proteins, including cuticular proteins, enzymes involved in the detoxification (cytochrome P450, glutathione S-transferases, esterase, ATP-binding cassette) and some biological pathways (oxidative phosphorylation, hippo signalling) that are potentially involved in cypermethrin resistance, was observed. Thirty-one representative DEPs (cytochrome P450, glutathione S-transferase, cuticle protein) during Cx. pipiens pallens developmental stages were confirmed by a parallel reaction monitoring strategy.

CONCLUSIONS

The present study confirmed the power of isobaric tags for relative and absolute quantification for identifying concomitantly quantitative proteome changes associated with cypermethrin in Cx. pipiens pallens. Proteome analysis suggests that proteome modifications can be selected rapidly by cypermethrin, and multiple resistance mechanisms operate simultaneously in cypermethrin-resistance of Cx. pipiens pallens, Our results interpret that an up-regulated expression of proteins and enzymes like cytochrome P450, glutathione S-transferases, esterase etc. has an impact in insecticide resistance. Previously neglected penetration resistance (cuticular proteins) may play an important role in the adaptive response of Cx. pipiens pallens to insecticides. This information may serve as a basis for future work concerning the possible role of these proteins in cypermethrin resistance in mosquito Cx. pipiens pallens. © 2022 Society of Chemical Industry.

Knockdown or inhibition of arginine kinases enhances susceptibility of Tribolium castaneum to deltamethrin

Metabolism of insecticides is an energy-consuming process. As an important component of the intracellular energy buffering system, arginine kinase (AK) plays an important role in insect cellular energy homeostasis and environmental stress response, but the involvement of AKs in the response to chemical stressors (insecticides) remains largely unknown. In this study, using Tribolium castaneum as a model organism, we found that deltamethrin treatment significantly upregulated the expression of TcAK1 and TcAK2 and decreased the whole body ATP content. The knockdown of TcAK1 or TcAK2 significantly enhances the deltamethrin-induced ATP depletion and increase the susceptibility of T. castaneum to deltamethrin. In addition, pretreatment with two AK inhibitors, rutin and quercetin, significantly decreased the lifespan of beetles treated with deltamethrin. These results suggest that AKs might be involved in detoxification of insecticides by regulating cellular energy balance.

Inductions of a CYP6 cluster conferring deltamethrin resistance in colonized and field-collected Culex pipiens pallens

Mosquitoes transmit many damaging vector-borne diseases. Unfortunately, the rise of insecticide resistance has become a major obstacle to mosquito control. A preliminary study showed that a CYP6 cluster is significant for deltamethrin resistance in colonized Culex pipiens pallens. Here, several field strains were collected to explore the association of the cluster in deltamethrin tolerance. We examined the effect of deltamethrin treatment on the cluster expression at a deltamethrin concentration of LC₅₀ in these strains using five time points. As a result, both P450 induction and constitutive overexpression were associated with deltamethrin resistance. Deltamethrin could stimulate different expression sets in the P450 cluster in different strains, predominately correlated with the resistance level of the strain. Our results will offer more insight into working with the characterization of P450s related to insecticide resistance.

Integration of transcriptome and proteome reveals molecular mechanisms underlying stress responses of the cutworm, Spodoptera litura, exposed to different levels of lead (Pb)

Heavy metals are major environmental pollutants that affect organisms across different trophic levels. Herbivorous insects play an important role in the bioaccumulation, and eventually, biomagnification of these metals. Although effects of heavy metal stress on insects have been well-studied, the molecular mechanisms underlying their effects remain poorly understood. Here, we used the RNA-Seq profiling and isobaric tags for relative and absolute quantitation (iTRAQ) approaches to unravel these mechanisms in the polyphagous pest Spodoptera litura exposed to lead (Pb) at two different concentrations (12.5 and 100 mg Pb/kg; PbL and PbH, respectively). Altogether, 1392 and 1630 differentially expressed genes (DEGs) and 58, 114 differentially expressed proteins (DEPs) were identified in larvae exposed to PbL and PbH, respectively. After exposed to PbL, the main up-regulated genes clusters and proteins in S. litura larvae were associated with their metabolic processes, including carbohydrate, protein, and lipid metabolism, but the levels of cytochrome P450 associated with the pathway of xenobiotic biodegradation and metabolism were found to be decreased. In contrast, the main up-regulated genes clusters and proteins in larvae exposed to PbH were enriched in the metabolism of xenobiotic by cytochrome P450, drug metabolism-cytochrome P450, and other drug metabolism enzymes, while the down-regulated genes and proteins were found to be closely related to the lipid (lipase) and protein (serine protease, trypsin) metabolism and growth processes (cuticular protein). These findings indicate that S. litura larvae exposed to PbL could enhance food digestion and absorption to prioritize for growth rather than detoxification, whereas S. litura larvae exposed to PbH reduced food digestion and absorption and channelized the limited energy for detoxification rather than growth. These contrasting results explain the dose-dependent effects of heavy metal stress on insect life-history traits, wherein low levels of heavy metal stress induce stimulation, while high levels of heavy metal stress cause inhibition at the transcriptome and proteome levels.

Evaluation of Total Female and Male Aedes aegypti Proteomes Reveals Significant Predictive Protein-Protein Interactions, Functional Ontologies, and Differentially Abundant Proteins

Simple Summary

Aedes aegypti is a significant vector for flavivirus diseases. Only the female mosquito transmits pathogens, while the male plays a vital role in mating and species continuity. In this study, female and male Ae. aegypti proteins were analysed using a mass analyser. Then, we identified proteins for the examination of protein-protein interactions, functional enrichment, and differential protein abundance analysis. This study identified 422 and 682 proteins exclusive to male and female Ae. aegypti, respectively, with 608 proteins found in both sexes. The most significant protein-protein interaction clusters and functional enrichments were observed in the biological process, molecular function, and cellular component for the proteins of both sexes. The abundance of the proteins differed, with one protein showing an increase (elongation factor 1 α, EF1α) and two showing reductions (actin family) in females versus males. The study highlights the protein differences in male and female Ae. aegypti, and future research could further investigate their roles in mosquito–viral interactions for blocking disease transmission.

Abstract

Aedes aegypti is a significant vector for many tropical and subtropical flavivirus diseases. Only the female mosquito transmits pathogens, while the male plays a vital role in mating and species continuity. This study explored the total proteomes of females and males based on the physiological and genetic differences of female and male mosquitoes. Protein extracts from mosquitoes were analysed using LC–ESI–MS/MS for protein identification, protein interaction network analysis, functional ontology enrichment, and differential protein abundance analyses. Protein identification revealed 422 and 682 proteins exclusive to males and females, respectively, with 608 common proteins found in both sexes. The most significant PPIs (<1.0 × 10⁻¹⁶) were for common proteins, followed by proteins exclusive to females (<1.0 × 10⁻¹⁶) and males (1.58 × 10⁻¹²). Significant functional enrichments were observed in the biological process, molecular function, and cellular component for the male and female proteins. The abundance of the proteins differed, with one protein showing an increase (elongation factor 1 α, EF1α) and two showing reductions (actin family) in females versus males. Overall, the study verified the total proteomes differences between male and female Ae. aegypti based on protein identification and interactions, functional ontologies, and differentially abundant proteins. Some of the identified proteins merit further investigation to elucidate their roles in blocking viral transmission.

Comparative proteomics reveals mechanisms that underlie insecticide resistance in Culex pipiens pallens Coquillett

Mosquito control based on chemical insecticides is considered as an important element of the current global strategies for the control of mosquito-borne diseases. Unfortunately, the development of insecticide resistance of important vector mosquito species jeopardizes the effectiveness of insecticide-based mosquito control. In contrast to target site resistance, other mechanisms are far from being fully understood. Global protein profiles among cypermethrin-resistant, propoxur-resistant, dimethyl-dichloro-vinyl-phosphate-resistant and susceptible strain of Culex pipiens pallens were obtained and proteomic differences were evaluated by using isobaric tags for relative and absolute quantification labeling coupled with liquid chromatography/tandem mass spectrometric analysis. A susceptible strain of Culex pipiens pallens showed elevated resistance levels after 25 generations of insecticide selection, through iTRAQ data analysis detected 2,502 proteins, of which 1,513 were differentially expressed in insecticide-selected strains compared to the susceptible strain. Finally, midgut differential protein expression profiles were analyzed, and 62 proteins were selected for verification of differential expression using iTRAQ and parallel reaction monitoring strategy, respectively. iTRAQ profiles of adaptation selection to three insecticide strains combined with midgut profiles revealed that multiple insecticide resistance mechanisms operate simultaneously in resistant insects of Culex pipiens pallens. Significant molecular resources were developed for Culex pipiens pallens, potential candidates were involved in metabolic resistance and reducing penetration or sequestering insecticide. Future research that is targeted towards RNA interference of the identified metabolic targets, such as cuticular proteins, cytochrome P450s, glutathione S-transferases and ribosomal proteins proteins and biological pathways (drug metabolism—cytochrome P450, metabolism of xenobiotics by cytochrome P450, oxidative phosphorylation, ribosome) could lay the foundation for a better understanding of the genetic basis of insecticide resistance in Culex pipiens pallens.

Global protein profiles were compared among a susceptible strain of Cx. pipiens pallens and strains that were cypermethrin-resistant, propoxur-resistant, and dimethyl-dichloro-vinyl-phosphate-resistant after 25 generations of selection by distinct chemical insecticide families, multiple mechanisms were found to operate simultaneously in resistant mosquitoes of Cx. pipiens pallens, including mechanisms to lower penetration of or sequester the insecticide or to increase biodegradation of the insecticide via subtle alterations in either the cuticular protein levels or the activities of detoxification enzymes (P450s and glutathione S-transferases).

From Global to Local-New Insights into Features of Pyrethroid Detoxification in Vector Mosquitoes

The threat of mosquito-borne diseases continues to be a problem for public health in subtropical and tropical regions of the world; in response, there has been increased use of adulticidal insecticides, such as pyrethroids, in human habitation areas over the last thirty years. As a result, the prevalence of pyrethroid-resistant genetic markers in natural mosquito populations has increased at an alarming rate. This review details recent advances in the understanding of specific mechanisms associated with pyrethroid resistance, with emphasis on features of insecticide detoxification and the interdependence of multiple cellular pathways. Together, these advances add important context to the understanding of the processes that are selected in resistant mosquitoes. Specifically, before pyrethroids bind to their targets on motoneurons, they must first permeate the outer cuticle and diffuse to inner tissues. Resistant mosquitoes have evolved detoxification mechanisms that rely on cytochrome P450s (CYP), esterases, carboxyesterases, and other oxidation/reduction (redox) components to effectively detoxify pyrethroids to nontoxic breakdown products that are then excreted. Enhanced resistance mechanisms have evolved to include alteration of gene copy number, transcriptional and post-transcriptional regulation of gene expression, as well as changes to cellular signaling mechanisms. Here, we outline the variety of ways in which detoxification has been selected in various mosquito populations, as well as key gene categories involved. Pathways associated with potential new genes of interest are proposed. Consideration of multiple cellular pathways could provide opportunities for development of new insecticides.

Evaluation of female Aedes aegypti proteome via LC-ESI-MS/MS using two protein extraction methods

Background

Proteomic analyses have broadened the horizons of vector control measures by identifying proteins associated with different biological and physiological processes and give further insight into the mosquitoes’ biology, mechanism of insecticide resistance and pathogens-mosquitoes interaction. Female Ae. aegypti ingests human blood to acquire the requisite nutrients to make eggs. During blood ingestion, female mosquitoes transmit different pathogens. Therefore, this study aimed to determine the best protein extraction method for mass spectrometry analysis which will allow a better proteome profiling for female mosquitoes.

Methods

In this present study, two protein extractions methods were performed to analyze female Ae. aegyti proteome, via TCA acetone precipitation extraction method and a commercial protein extraction reagent CytoBuster^TM. Then, protein identification was performed by LC-ESI-MS/MS and followed by functional protein annotation analysis.

Results

The CytoBuster^TM reagent gave the highest protein yield with a mean of 475.90 µg compared to TCA acetone precipitation extraction showed 283.15 µg mean of protein. LC-ESI-MS/MS identified 1,290 and 890 proteins from the CytoBuster^TM reagent and TCA acetone precipitation, respectively. When comparing the protein class categories in both methods, there were three additional categories for proteins identified using CytoBuster^TM reagent. The proteins were related to scaffold/adaptor protein (PC00226), protein binding activity modulator (PC00095) and intercellular signal molecule (PC00207). In conclusion, the CytoBuster^TM protein extraction reagent showed a better performance for the extraction of proteins in term of the protein yield, proteome coverage and extraction speed.

De Novo Transcriptomic Analyses Revealed Some Detoxification Genes and Related Pathways Responsive to Noposion Yihaogong® 5% EC (Lambda-Cyhalothrin 5%) Exposure in Spodoptera frugiperda Third-Instar Larvae

Simple Summary

Insect pest resistance to synthetic insecticides is a major problem that limits efficient management and thus decreases productivity for farmers and increases the use of harmful materials that pollute the environment and endanger humans and beneficial organisms. A major approach for resistance management is understanding how insect pest field populations develop resistance at molecular levels. To provide a comprehensive insight into the resistance mechanisms of Spodoptera frugiperda larvae to lambda-cyhalothrin 5%, we investigated the molecular basis of resistance mechanism in field collected population of fall armyworm (Spodoptera frugiperda) to lambda-cyhalothrin 5% insecticide, a pyrethroid insecticide by using de novo transcriptomics analysis. We found that resistance to lambda-cyhalothrin 5% can be metabolic by increasing the levels of detoxifying enzymes such as P450, GST and UGT and related genes to insecticide resistance in the field population. The obtained transcriptome information provides large gene resources available for further studying the resistance development of Spodoptera frugiperda to pesticides. The DGE data provide comprehensive insights into the gene expression profiles of fall armyworm (Spodoptera frugiperda) to lambda-cyhalothrin 5% and will facilitate the study of the role of each gene in lambda-cyhalothrin resistance development.

Abstract

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a polyphagous, invasive insect pest which causes significant losses in important crops wherever it has spread. The use of pesticides in agriculture is a key tool in the management of many important crop pests, including S. frugiperda, but continued use of insecticides has selected for various types of resistance, including enzyme systems that provide enhanced mechanisms of detoxification. In the present study, we analyzed the de novo transcriptome of S. frugiperda larvae exposed to Noposion Yihaogong^® 5% emulsifiable concentrate (EC) insecticide focusing on detoxification genes and related pathways. Results showed that a total of 1819 differentially expressed genes (DEGs) were identified in larvae after being treated with Noposion Yihaogong^® 5% EC insecticide, of which 863 were up- and 956 down-regulated. Majority of these differentially expressed genes were identified in numerous Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including metabolism of xenobiotics and drug metabolism. Furthermore, many of S. frugiperda genes involved in detoxification pathways influenced by lambda-cyhalothrin stress support their predicted role by further co-expression network analysis. Our RT-qPCR results were consistent with the DEG’s data of transcriptome analysis. The comprehensive transcriptome sequence resource attained through this study enriches the genomic platform of S. frugiperda, and the identified DEGs may enable greater molecular underpinnings behind the insecticide-resistance mechanism caused by lambda-cyhalothrin.

Proteomic Analyses Detect Higher Expression of C-Type Lectins in Imidacloprid-Resistant Colorado Potato Beetle Leptinotarsa decemlineata Say

Simple Summary

Surveillance and determining the mechanisms of pesticide resistance are key components of resistance management. Mechanisms can be investigated using biochemical, genomic, proteomic and other modern analytical techniques. In the present study, proteomic analyses of Colorado potato beetle (CPB), one of the most adaptable insect pests to both plant toxins and synthetic insecticides, were applied to identify protein differences in insecticide-susceptible and resistant strains. Proteins identified in abdominal and midgut tissues based on separating by 2-dimensional (2-D) gels and mass spectrometry were associated with insect innate immunity. A database search found that the highest match was a C-type lectin (CTL), which is a component in the insect’s innate immune system. The 2-D gel spot identified as a CTL was greater in the insecticide-resistant CPB strain, but the CTL spot size was increased by exposure to imidacloprid in the susceptible strain. This is a novel finding, which suggests that CTLs and insect immunity may respond to certain toxins as well as to pathogens. There may also be a potential application for pest management if insect immunity is targeted.

Abstract

The Colorado potato beetle (CPB) is one of the most adaptable insect pests to both plant toxins and synthetic insecticides. Resistance in CPB is reported for over 50 classes of insecticides, and mechanisms of insecticide-resistance include enhanced detoxification enzymes, ABC transporters and target site mutations. Adaptation to insecticides is also associated with changes in behaviour, energy metabolism and other physiological processes seemingly unrelated to resistance but partially explained through genomic analyses. In the present study, in place of genomics, we applied 2-dimensional (2-D) gel and mass spectrometry to investigate protein differences in abdominal and midgut tissue of insecticide-susceptible (S) and -resistant (R) CPB. The proteomic analyses measured constitutive differences in several proteins, but the highest match was identified as a C-type lectin (CTL), a component of innate immunity in insects. The constitutive expression of the CTL was greater in the multi-resistant (LI) strain, and the same spot was measured in both midgut and abdominal tissue. Exposure to the neonicotinoid insecticide, imidacloprid, increased the CTL spot found in the midgut but not in the abdominal tissue of the laboratory (Lab) strain. No increase in protein levels in the midgut tissue was observed in the LI or a field strain (NB) tolerant to neonicotinoids. With the exception of biopesticides, such as Bacillus thuringiensis (Bt), no previous studies have documented differences in the immune response by CTLs in insects exposed to synthetic insecticides or the fitness costs associated with expression levels of immune-related genes in insecticide-resistant strains. This study demonstrates again how CPB has been successful at adapting to insecticides, plant defenses as well as pathogens.

Chironomus riparius Proteome Responses to Spinosad Exposure

The potential of proteome responses as early-warning indicators of insecticide exposure was evaluated using the non-biting midge Chironomus riparius (Meigen) as the model organism. Chironomus riparius larvae were exposed to environmentally relevant concentrations of the neurotoxic pesticide spinosad to uncover molecular events that may provide insights on the long-term individual and population level consequences. The iTRAQ labeling method was performed to quantify protein abundance changes between exposed and non-exposed organisms. Data analysis revealed a general dose-dependent decrease in the abundance of globin proteins as a result of spinosad exposure. Additionally, the downregulation of actin and a larval cuticle protein was also observed after spinosad exposure, which may be related to previously determined C. riparius life-history traits impairment and biochemical responses. Present results suggest that protein profile changes can be used as early warning biomarkers of pesticide exposure and may provide a better mechanistic interpretation of the toxic response of organisms, aiding in the assessment of the ecological effects of environmental contamination. This work also contributes to the understanding of the sublethal effects of insecticides in invertebrates and their molecular targets.

Transcriptome Analysis and Identification of Insecticide Tolerance-Related Genes after Exposure to Insecticide in Sitobion avenae

Aphids cause serious losses to the production of wheat. The grain aphid, Sitobion avenae, which is the dominant species of aphid in all wheat regions of China, is resistant to a variety of insecticides, including imidacloprid and chlorpyrifos. However, the resistance and mechanism of insecticide tolerance of S. avenae are still unclear. Therefore, this study employed transcriptome analysis to compare the expression patterns of stress response genes under imidacloprid and chlorpyrifos treatment for 15 min, 3 h, and 36 h of exposure. S. avenae adult transcriptome was assembled and characterized first, after which samples treated with insecticides for different lengths of time were compared with control samples, which revealed 60–2267 differentially expressed unigenes (DEUs). Among these DEUs, 31–790 unigenes were classified into 66–786 categories of gene ontology (GO) functional groups, and 24–760 DEUs could be mapped into 54–268 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Finally, 11 insecticide-tolerance-related unigenes were chosen to confirm the relative expression by quantitative real-time polymerase chain reaction (qRT-PCR) in each treatment. Most of the results between qRT-PCR and RNA sequencing (RNA-Seq) are well-established. The results presented herein will facilitate molecular research investigating insecticide resistance in S. avenae, as well as in other wheat aphids.

Using targeted next-generation sequencing to characterize genetic differences associated with insecticide resistance in Culex quinquefasciatus populations from the southern U.S

Resistance to insecticides can hamper the control of mosquitoes such as Culex quinquefasciatus, known to vector arboviruses such as West Nile virus and others. The strong selective pressure exerted on a mosquito population by the use of insecticides can result in heritable genetic changes associated with resistance. We sought to characterize genetic differences between insecticide resistant and susceptible Culex quinquefasciatus mosquitoes using targeted DNA sequencing. To that end, we developed a panel of 122 genes known or hypothesized to be involved in insecticide resistance, and used an Ion Torrent PGM sequencer to sequence 125 unrelated individuals from seven populations in the southern U.S. whose resistance phenotypes to permethrin and malathion were known from previous CDC bottle bioassay testing. Data analysis consisted of discovering SNPs (Single Nucleotide Polymorphism) and genes with evidence of copy number variants (CNVs) statistically associated with resistance. Ten of the seventeen genes found to be present in higher copy numbers were experimentally validated with real-time PCR. Of those, six, including the gene with the knock-down resistance (kdr) mutation, showed evidence of a ≥ 1.5 fold increase compared to control DNA. The SNP analysis revealed 228 unique SNPs that had significant p-values for both a Fisher’s Exact Test and the Cochran-Armitage Test for Trend. We calculated the population frequency for each of the 64 nonsynonymous SNPs in this group. Several genes not previously well characterized represent potential candidates for diagnostic assays when further validation is conducted.

Caste- and pesticide-specific effects of neonicotinoid pesticide exposure on gene expression in bumblebees

Social bees are important insect pollinators of wildflowers and agricultural crops, making their reported declines a global concern. A major factor implicated in these declines is the widespread use of neonicotinoid pesticides. Indeed, recent research has demonstrated that exposure to low doses of these neurotoxic pesticides impairs bee behaviours important for colony function and survival. However, our understanding of the molecular-genetic pathways that lead to such effects is limited, as is our knowledge of how effects may differ between colony members. To understand what genes and pathways are affected by exposure of bumblebee workers and queens to neonicotinoid pesticides, we implemented a transcriptome-wide gene expression study. We chronically exposed Bombus terrestriscolonies to either clothianidin or imidacloprid at field-realistic concentrations while controlling for factors including colony social environment and worker age. We reveal that genes involved in important biological processes including mitochondrial function are differentially expressed in response to neonicotinoid exposure. Additionally, clothianidin exposure had stronger effects on gene expression amplitude and alternative splicing than imidacloprid. Finally, exposure affected workers more strongly than queens. Our work demonstrates how RNA-Seq transcriptome profiling can provide detailed novel insight on the mechanisms mediating pesticide toxicity to a key insect pollinator.

3,4-Dihydroxyphenylacetaldehyde synthase and cuticle formation in insects

Cuticle is the most important structure that protects mosquitoes and other insect species from adverse environmental conditions and infections of microorganism. The physiology and biochemistry of insect cuticle formation have been studied for many years and our understanding of cuticle formation and hardening has increased considerably. This is especially true for flexible cuticle. The recent discovery of a novel enzyme that catalyzes the production of 3,4-dihydroxyphenylacetaldehyde (DOPAL) in insects provides intriguing insights concerning the flexible cuticle formation in insects. For convenience, the enzyme that catalyzes the production DOPAL from l-dopa is named DOPAL synthase. In this mini-review, we summarize the biochemical pathways of cuticle formation and hardening in general and discuss DOPAL synthase-mediated protein crosslinking in insect flexible cuticle in particular.

Differential proteomic analysis reveals sequential heat stress-responsive regulatory network in radish (Raphanus sativus L.) taproot

Differential abundance protein species (DAPS) involved in reducing damage and enhancing thermotolerance in radish were firstly identified. Proteomic analysis and omics association analysis revealed a HS-responsive regulatory network in radish. Heat stress (HS) is a major destructive factor influencing radish production and supply in summer, for radish is a cool season vegetable crop being susceptible to high temperature. In this study, the proteome changes of radish taproots under 40 °C treatment at 0 h (Control), 12 h (Heat12) and 24 h (Heat24) were analyzed using iTRAQ (Isobaric Tag for Relative and Absolute Quantification) approach. In total, 2258 DAPS representing 1542 differentially accumulated uniprotein species which respond to HS were identified. A total of 604, 910 and 744 DAPS was detected in comparison of Control vs. Heat12, Control vs. Heat24, and Heat12 vs. Heat24, respectively. Gene ontology and pathway analysis showed that annexin, ubiquitin-conjugating enzyme, ATP synthase, heat shock protein (HSP) and other stress-related proteins were predominately enriched in signal transduction, stress and defense pathways, photosynthesis and energy metabolic pathways, working cooperatively to reduce stress-induced damage in radish. Based on iTRAQ combined with the transcriptomics analysis, a schematic model of a sequential HS-responsive regulatory network was proposed. The initial sensing of HS occurred at the plasma membrane, and then key components of stress signal transduction triggered heat-responsive genes in the plant protective metabolism to re-establish homeostasis and enhance thermotolerance. These results provide new insights into characteristics of HS-responsive DAPS and facilitate dissecting the molecular mechanisms underlying heat tolerance in radish and other root crops.

Pyrethroid Resistance in the Major Malaria Vector Anopheles funestus is Exacerbated by Overexpression and Overactivity of the P450 CYP6AA1 Across Africa

Resistance to pyrethroids (the ingredients in bed net insecticides) in the major malaria vector Anopheles funestus is threatening recent gains in the fight against malaria. Here, we established the role of an over-expressed P450, A. funestus CYP6AA1 in insecticides resistance. Transcription profiling of CYP6AA1 across Africa using microarray and quantitative reverse transcription polymerase chain reaction (qRT-PCR) revealed that it is significantly more over-expressed in southern African populations compared to West (Benin) and East African (Uganda). Heterologous expression in Escherichia coli coupled with metabolism assays demonstrated that CYP6AA1 metabolises type I (permethrin) and type II (deltamethrin) pyrethroids, as well as bendiocarb (a carbamate). Transgenic Drosophila melanogaster flies over-expressing CYP6AA1 were significantly more resistant to pyrethroid insecticides, permethrin and deltamethrin compared with control flies not expressing the gene, validating the role of this gene in pyrethroid resistance. In silico modelling and docking simulations predicted the intermolecular receptor-ligand interactions which allow this P450 to metabolise the pyrethroids and bendiocarb. Validation of CYP6AA1 as a pyrethroid resistance gene makes it possible to monitor the spread of resistance in the field where this P450 is over-expressed. Its potential cross-resistance role makes it necessary to monitor the gene closely to inform control programs on molecular basis of multiple resistance in the field.

Culex pipiens pallens cuticular protein CPLCG5 participates in pyrethroid resistance by forming a rigid matrix

Background

Chemical insecticides have hugely reduced the prevalence of vector-borne diseases around the world, but resistance threatens their continued effectiveness. Despite its importance, cuticle resistance is an under-studied area, and exploring the detailed molecular basis of resistance is critical for implementing suitable resistance management strategies.

Methods

We performed western blotting of cuticular protein CPLCG5 in deltamethrin-susceptible (DS) and laboratory-produced deltamethrin-resistant (DR) strains of Culex pipiens pallens. Immunofluorescence assays using a polyclonal antibody to locate cuticular CPLCG5 in mosquitoes. EM immunohistochemical analysis of the femur segment was used to compare the cuticle in control and CPLCG5-deficient siRNA experimental groups.

Results

The gene CPLCG5 encodes a cuticle protein that plays an important role in pyrethroid resistance. Based on a prior study, we found that expression of CPLCG5 was higher in the resistant (DR) strain than the susceptible (DS) strain. CPLCG5 transcripts were abundant in white pupae and 1-day-old adults, but expression was dramatically decreased in 3-day-old adults, then remained stable thereafter. Western blotting revealed that the CPLCG5 protein was ~2.2-fold higher in the legs of the DR strain than the DS strain. Immunofluorescence assays revealed CPLCG5 expression in the head, thorax, abdomen, wing, and leg, and expression most abundant in the leg and wing. EM immunohistochemical analysis suggested that the exocuticle thickness of the femur was significantly thinner in the CPLCG5-deficient siCPLCG5 strain (0.717 ± 0.110 μm) than the siNC strain (0.946 ± 0.126 μm). Depletion of CPLCG5 by RNA interference resulted in unorganised laminae and a thinner cuticle.

Conclusions

The results suggest CPLCG5 participates in pyrethroid resistance by forming a rigid matrix and increasing the thickness of the cuticle.

Electronic supplementary material

The online version of this article (doi: 10.1186/s13071-017-2567-9) contains supplementary material, which is available to authorized users.

BdorOBP2 plays an indispensable role in the perception of methyl eugenol by mature males of Bactrocera dorsalis (Hendel)

Bactrocera dorsalis (Hendel) is a fruit-eating pest that causes substantial economic damage to the fresh produce industry in tropical and sub-tropical countries. Methyl eugenol (ME) is a powerful attractant for mature males of B. dorsalis, and has been widely used for detecting, luring and eradicating B. dorsalis populations worldwide. However, the molecular mechanism underlying the olfactory perception of ME remains largely unknown. Here, we analyzed the differential proteomics profiling of the antennae between ME-responsive and ME-non-responsive males by using isobaric tags for relative and absolute quantitation (iTRAQ). In total, 4622 proteins were identified, of which 277 proteins were significant differentially expressed, with 192 up-regulated and 85 down-regulated in responsive male antennae. Quantitative real-time PCR (qRT-PCR) analysis confirmed the authenticity and accuracy of the proteomic analysis. Based on the iTRAQ and qRT-PCR results, we found that the odorant-binding protein 2 (BdorOBP2) was abundantly expressed in responsive male antennae. Moreover, BdorOBP2 was significantly up-regulated by ME in male antennae. Mature males showed significantly greater taxis toward ME than did mature females. Silencing BdorOBP2 reduced mature males' responsiveness to ME. These results indicate that BdorOBP2 may play an essential role in the molecular mechanism underlying B. dorsalis olfactory perception of ME.

Using Next-Generation Sequencing to Detect Differential Expression Genes in Bradysia odoriphaga after Exposure to Insecticides

Bradysia odoriphaga (Diptera: Sciaridae) is the most important pest of Chinese chive. Insecticides are used widely and frequently to control B. odoriphaga in China. However, the performance of the insecticides chlorpyrifos and clothianidin in controlling the Chinese chive maggot is quite different. Using next generation sequencing technology, different expression unigenes (DEUs) in B. odoriphaga were detected after treatment with chlorpyrifos and clothianidin for 6 and 48 h in comparison with control. The number of DEUs ranged between 703 and 1161 after insecticide treatment. In these DEUs, 370–863 unigenes can be classified into 41–46 categories of gene ontology (GO), and 354–658 DEUs can be mapped into 987–1623 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The expressions of DEUs related to insecticide-metabolism-related genes were analyzed. The cytochrome P450-like unigene group was the largest group in DEUs. Most glutathione S-transferase-like unigenes were down-regulated and most sodium channel-like unigenes were up-regulated after insecticide treatment. Finally, 14 insecticide-metabolism-related unigenes were chosen to confirm the relative expression in each treatment by quantitative Real Time Polymerase Chain Reaction (qRT-PCR). The results of qRT-PCR and RNA Sequencing (RNA-Seq) are fairly well-established. Our results demonstrate that a next-generation sequencing tool facilitates the identification of insecticide-metabolism-related genes and the illustration of the insecticide mechanisms of chlorpyrifos and clothianidin.

Comparative proteomic analysis of autotetraploid and diploid Paulownia tomentosa reveals proteins associated with superior photosynthetic characteristics and stress adaptability in autotetraploid Paulownia

To enlarge the germplasm resource of Paulownia plants, we used colchicine to induce autotetraploid Paulownia tomentosa, as reported previously. Compared with its diploid progenitor, autotetraploid P. tomentosa exhibits better photosynthetic characteristics and higher stress resistance. However, the underlying mechanism for its predominant characteristics has not been determined at the proteome level. In this study, isobaric tag for relative and absolute quantitation coupled with liquid chromatography-tandem mass spectrometry was employed to compare proteomic changes between autotetraploid and diploid P. tomentosa. A total of 1427 proteins were identified in our study, of which 130 proteins were differentially expressed between autotetraploid and diploid P. tomentosa. Functional analysis of differentially expressed proteins revealed that photosynthesis-related proteins and stress-responsive proteins were significantly enriched among the differentially expressed proteins, suggesting they may be responsible for the photosynthetic characteristics and stress adaptability of autotetraploid P. tomentosa. The correlation analysis between transcriptome and proteome data revealed that only 15 (11.5%) of the differentially expressed proteins had corresponding differentially expressed unigenes between diploid and autotetraploid P. tomentosa. These results indicated that there was a limited correlation between the differentially expressed proteins and the previously reported differentially expressed unigenes. This work provides new clues to better understand the superior traits in autotetraploid P. tomentosa and lays a theoretical foundation for developing Paulownia breeding strategies in the future.

Transcriptome Sequencing Analysis and Functional Identification of Sex Differentiation Genes from the Mosquito Parasitic Nematode, Romanomermis wuchangensis

Mosquito-transmitted diseases like malaria and dengue fever are global problem and an estimated 50–100 million of dengue or dengue hemorrhagic fever cases are reported worldwide every year. The mermithid nematode Romanomermis wuchangensis has been successfully used as an ecosystem-friendly biocontrol agent for mosquito prevention in laboratory studies. However, this nematode can not undergo sex differentiation in vitro culture, which has seriously affected their application of biocontrol in the field. In this study, based on transcriptome sequencing analysis of R. wuchangensis, Rwucmab-3, Rwuclaf-1 and Rwuctra-2 were cloned and used to investigate molecular regulatory function of sex differentiation. qRT-PCR results demonstrated that the expression level of Rwucmab-3 between male and female displayed obvious difference on the 3^rd day of parasitic stage, which was earlier than Rwuclaf-1 and Rwuctra-2, highlighting sex differentiation process may start on the 3^rd day of parasitic stage. Besides, FITC was used as a marker to test dsRNA uptake efficiency of R. wuchangensis, which fluorescence intensity increased with FITC concentration after 16 h incubation, indicating this nematode can successfully ingest soaking solution via its cuticle. RNAi results revealed the sex ratio of R. wuchangensis from RNAi treated groups soaked in dsRNA of Rwucmab-3 was significantly higher than gfp dsRNA treated groups and control groups, highlighting RNAi of Rwumab-3 may hinder the development of male nematodes. These results suggest that Rwucmab-3 mainly involves in the initiation of sex differentiation and the development of male sexual dimorphism. Rwuclaf-1 and Rwuctra-2 may play vital role in nematode reproductive and developmental system. In conclusion, transcript sequences presented in this study could provide more bioinformatics resources for future studies on gene cloning and other molecular regulatory mechanism in R. wuchangensis. Moreover, identification and functional analysis of sex differentiation genes may clarify the sex differentiation mechanism of R. wuchangensis, which are helpful to solve the uncompleted sex differentiation problem in vitro culture and the potential large-scale field application controlling the larvae of C. quinquefasciatus, A. aegypti and A. albopictus.

Differential protein expression in the midgut of Culex quinquefasciatus mosquitoes induced by the insecticide temephos

Mosquitoes are vectors for pathogens of malaria, lymphatic filariasis, dengue, chikungunya, yellow fever and Japanese encephalitis. Culex quinquefasciatus Say, 1823 (Diptera: Culicidae) is a known vector of lymphatic filariasis. Its control in Brazil has been managed using the organophosphate temephos. Studies examining the proteins of Cx. quinquefasciatus that are differentially expressed in response to temephos further understanding of the modes of action of the insecticide and may potentially identify resistance factors in the mosquito. In the present study, a comparative proteomic analysis, using 2-dimensional electrophoresis coupled with matrix-assisted laser desorption/ionization (MALDI) time of flight (TOF)/TOF mass spectrometry, and bioinformatics analyses were performed to identify midgut proteins in Cx. quinquefasciatus larvae that were differentially expressed in response to exposure to temephos relative to those in untreated controls. A total of 91 protein spots were differentially expressed; 40 were upregulated and 51 were downregulated by temephos. A total of 22 proteins, predominantly upregulated, were identified as known to play a role in the immune response, whereas the downregulated proteins were involved in energy and protein catabolism. This is the first proteome study of the midgut of Cx. quinquefasciatus and it provides insights into the molecular mechanisms of insecticide-induced responses in the mosquito.

Identification of protease m1 zinc metalloprotease conferring resistance to deltamethrin by characterization of an AFLP marker in Culex pipiens pallens

BACKGROUND

Continuous and excessive application of deltamethrin (DM) has resulted in the rapid development of insecticide resistance in Culex pipiens pallens. The quantitative trait loci (QTL) responsible for resistance to DM had previously been detected in Cx. pipiens pallens. But locating the QTLs on the chromosomes remained difficult. An available approach is to first characterize DNA molecular markers linked with the phenotype, and then identify candidate genes.

METHODS

In this study, the amplified fragment length polymorphism (AFLP) marker L3A8.177 associated with the QTL, was characterized. We searched for potential candidate genes in the flank region of L3A8.177 in the genome sequence of the closely related Cx. pipiens quinquefasciatus and conducted mRNA expression analysis of the candidate gene via quantitative real-time PCR. Then the relationship between DM resistance and the candidate gene was identified using RNAi and American CDC Bottle Bioassay in vivo. We also cloned the ORF sequences of the candidate gene from both susceptible and resistant mosquitoes.

RESULTS

The genes CYP6CP1 and protease m1 zinc metalloprotease were in the flank region of L3A8.177 and had significantly different expression levels between susceptible and resistant strains. Protease m1 zinc metalloprotease was significantly up-regulated in the susceptible strains compared with the resistant and remained over-expressed in the susceptible field-collected strains. For deduced amino acid sequences of protease m1 zinc metalloprotease, there was no difference between susceptible and resistant mosquitoes. Knockdown of protease m1 zinc metalloprotease not only decreased the sensitivity of mosquitoes to DM in the susceptible strain but also increased the expression of CYP6CP1, suggesting the role of protease m1 zinc metalloprotease in resistance may be involved in the regulation of the P450 gene expression.

CONCLUSION

Our study represents an example of candidate genes derived from the AFLP marker associated with the QTL and provides the first evidence that protease m1 zinc metalloprotease may play a role in the regulation of DM resistance in Cx. pipiens pallens.

Identification of QTLs Conferring Resistance to Deltamethrin in Culex pipiens pallens

Culex pipiens pallens is the most abundant Culex mosquito species in northern China and is an important vector of bancroftian filariasis and West Nile virus. Deltamethrin is an insecticide that is widely used for mosquito control, however resistance to this and other insecticides has become a major challenge in the control of vector-borne diseases that appear to be inherited quantitatively. Furthermore, the genetic basis of insecticide resistance remains poorly understood. In this study, quantitative trait loci (QTL) mapping of resistance to deltamethrin was conducted in F₂ intercross segregation populations using bulked segregation analysis (BSA) and amplified fragment length polymorphism markers (AFLP) in Culex pipiens pallens. A genetic linkage map covering 381 cM was constructed and a total of seven QTL responsible for resistance to deltamethrin were detected by composite interval mapping (CIM), which explained 95% of the phenotypic variance. The major QTL in linkage group 2 accounted for 62% of the variance and is worthy of further study. 12 AFLP markers in the map were cloned and the genomic locations of these marker sequences were determined by applying the Basic Local Alignment Search Tool (BLAST) tool to the genome sequence of the closely related Culex quinquefasciatus. Our results suggest that resistance to deltamethrin is a quantitative trait under the control of a major QTL in Culex pipiens pallens. Cloning of related AFLP markers confirm the potential utility for anchoring the genetic map to the physical map. The results provide insight into the genetic architecture of the trait.

Proteomic analysis of endoplasmic reticulum stress responses in rice seeds

The defects in storage proteins secretion in the endosperm of transgenic rice seeds often leads to endoplasmic reticulum (ER) stress, which produces floury and shrunken seeds, but the mechanism of this response remains unclear. We used an iTRAQ-based proteomics analysis of ER-stressed rice seeds due to the endosperm-specific suppression of OsSar1 to identify changes in the protein levels in response to ER stress. ER stress changed the expression of 405 proteins in rice seed by >2.0- fold compared with the wild-type control. Of these proteins, 140 were upregulated and 265 were downregulated. The upregulated proteins were mainly involved in protein modification, transport and degradation, and the downregulated proteins were mainly involved in metabolism and stress/defense responses. A KOBAS analysis revealed that protein-processing in the ER and degradation-related proteasome were the predominant upregulated pathways in the rice endosperm in response to ER stress. Trans-Golgi protein transport was also involved in the ER stress response. Combined with bioinformatic and molecular biology analyses, our proteomic data will facilitate our understanding of the systemic responses to ER stress in rice seeds.

The cuticle proteins: a putative role for deltamethrin resistance in Culex pipiens pallens

Insecticide resistance has been a major public health challenge. It is impendent to study the mechanism on insecticide resistance. In our previous study, 14 differentially accumulated insect cuticle proteins (ICPs) based on insecticide resistance proteomes and transcriptomes were found in the deltamethrin-resistant (DR) and -susceptible (DS) strains of Culex pipiens pallens. To investigate if these ICPs are associated with deltamethrin resistance, different transcriptional levels of the 14 ICPs were detected in the DS and DR strains from laboratory and field populations by using quantitative real-time polymerase chain reaction (qRT-PCR). The expression levels of the 14 ICPs were also measured after short-term exposure of the DS strain to deltamethrin. The full-length complementary DNA (cDNA) of CpCPLCG5 gene, which encodes one of the 14 ICPs, was cloned from Cx. pipiens pallens. Homology analysis and phylogenetic analysis were carried out with some other insects. Furthermore, small interfering RNA (siRNA) was used to knockdown the expression level of CpCPLCG5 gene for characterizing its contribution to deltamethrin resistance. The results showed that the expression level of CpCPLCG5 gene was higher in DR strain than in DS strain both in laboratory and field populations while the other 13 ICPs were downregulated. The full-length cDNA of CpCPLCG5 gene was 732 bp, with the ORF of 390 bp and deduced 129 amino acids (GenBank/KF723314,2013). Knockdown of CpCPLCG5 gene increased the susceptibility of the DR strain while the expression level of the other 13 ICPs elevated. Our findings indicate that the cuticle proteins are associated with deltamethrin resistance in Cx. pipiens pallens.