ATP-Binding Cassette (ABC) Transporter Genes Involved in Pyrethroid Resistance in the Malaria Vector Anopheles sinensis: Genome-Wide Identification, Characteristics, Phylogenetics, and Expression Profile

Characteristics of Trypsin genes and their roles in insecticide resistance based on omics and functional analyses in the malaria vector Anopheles sinensis

Trypsin is one of the most diverse and widely studied protease hydrolases. However, the diversity and characteristics of the Trypsin superfamily of genes have not been well understood, and their role in insecticide resistance is yet to be investigated. In this study, a total of 342 Trypsin genes were identified and classified into seven families based on homology, characteristic domains and phylogenetics in Anopheles sinensis, and the LY-Domain and CLECT-Domain families are specific to the species. Four Trypsin genes, (Astry2b, Astry43a, Astry90, Astry113c) were identified to be associated with pyrethroid resistance based on transcriptome analyses of three field resistant populations and qRT-PCR validation, and the knock-down of these genes significantly decrease the pyrethroid resistance of Anopheles sinensis based on RNAi. The activity of Astry43a can be reduced by five selected insecticides (indoxacarb, DDT, temephos, imidacloprid and deltamethrin); and however, the Astry43a could not directly metabolize these five insecticides, like the trypsin NYD-Tr did in earlier reports. This study provides the overall information frame of Trypsin genes, and proposes the role of Trypsin genes to insecticide resistance. Further researches are necessary to investigate the metabolism function of these trypsins to insecticides.

Involvement of miR-8510a-3p in response to Cry1Ac protoxin by regulating PxABCG3 in Plutella xylostella

Overuse of insecticides has accelerated the evolution of insecticide resistance and created serious environmental concerns worldwide, thus incentivizing development of alternative methods. Bacillus thuringiensis (Bt) is an insecticidal bacterium that has been developed as a biopesticide to successfully control multiple species of pests. It operates by secreting several insect toxins such as Cry1Ac. However, metabolic resistance based on ATP-binding cassette (ABC) transporters may play a crucial role in the development of metabolic resistance to Bt. Here, we characterized an ABCG gene from the agricultural pest Plutella xylostella (PxABCG3) and found that it was highly expressed in a Cry1Ac-resistant strain, up-regulated after Cry1Ac protoxin treatment. Binding miR-8510a-3p to the coding sequence (CDS) of PxABCG3 was then confirmed by a luciferase reporter assay and RNA immunoprecipitation. miR-8510a-3p agomir delivery markedly reduced PxABCG3 expression in vivo and consequently decreased the tolerance of P. xylostella to Cry1Ac, while reduction of miR-8510a-3p significantly increased PxABCG3 expression, accompanied by an increased tolerance to Cry1Ac. Our results suggest that miR-8510a-3p could potentially be used as a novel molecular target against P. xylostella or other lepidopterans, providing novel insights into developing effective and environmentally friendly pesticides.

Characterization and transcriptional expression of ABCG genes in Bactrocera dorsalis: Insights into their roles in fecundity and insecticidal stress response

The ATP-binding cassette (ABC) transporters are essential for regulating various physiological processes and insecticide resistance across different living organisms. ABCG subfamily genes have diverse functions in insects, but little is known about the function of ABCGs in a serious agricultural pest, Bactrocera dorsalis. In this study, 15 BdABCG genes were identified, and BdABCG6 and BdABCG11 were highly expressed in the pupal and adult stages, especially during the transition period from pupae to adults. Silencing of these two genes resulted in a significant reduction of egg production in B. dorsalis, confirming their importance in reproduction. Analysis of tissue expression patterns showed that most genes, including BdABCG1, 3, 8, and 14, exhibited tissue-specificity, with significantly higher expression levels observed in the intestine, Malpighian tubule, and fat body compared to other tissues. Meanwhile, the induction of malathion and avermectin can significantly upregulate the expression of the above four genes. Furthermore, knockdown of BdABCG3 by RNAi significantly increased the mortality of B. dorsalis upon exposure to avermectin, which suggested that BdABCG3 is involved in the transport or metabolism of avermectin in B. dorsalis. Overall, our work provides valuable insights into the function of BdABCGs involved in the reproduction and detoxification system of B. dorsalis.

Transcriptomic investigation of the molecular mechanisms underlying resistance to the neonicotinoid thiamethoxam and the pyrethroid lambda-cyhalothrin in Euschistus heros (Hemiptera: Pentatomidae)

BACKGROUND

Laboratory-selected resistant strains of Euschistus heros to thiamethoxam (NEO) and lambda-cyhalothrin (PYR) were recently reported in Brazil. However, the mechanisms conferring resistance to these insecticides in E. heros remain unresolved. We utilized comparative transcriptome profiling and single nucleotide polymorphism (SNP) calling of susceptible and resistant strains of E. heros to investigate the molecular mechanism(s) underlying resistance.

RESULTS

The E. heros transcriptome was assembled, generating 91 673 transcripts with a mean length of 720 bp and N50 of 1795 bp. Comparative gene expression analysis between the susceptible (SUS) and NEO strains identified 215 significantly differentially expressed (DE) transcripts. DE transcripts associated with the xenobiotic metabolism were all up-regulated in the NEO strain. The comparative analysis of the SUS and PYR strains identified 204 DE transcripts, including an esterase (esterase FE4), a glutathione-S-transferase, an ABC transporter (ABCC1) and aquaporins that were up-regulated in the PYR strain. We identified 9588 and 15 043 nonsynonymous SNPs in the PYR and NEO strains. One of the SNPs (D70N) detected in the NEO strain occurs in a subunit (α5) of the nAChRs, the target site of neonicotinoid insecticides. Nevertheless, this residue position in α5 is not conserved among insects.

CONCLUSIONS

Neonicotinoid and pyrethroid resistance in laboratory-selected E. heros is associated with a potential metabolic resistance mechanism by the overexpression of proteins commonly involved in the three phases of xenobiotic metabolism. Together these findings provide insight into the potential basis of resistance in E. heros and will inform the development and implementation of resistance management strategies against this important pest. © 2023 Society of Chemical Industry.

Identification and functional analysis of ABC transporter genes related to deltamethrin resistance in Culex pipiens pallens

BACKGROUND

Pathogens that reproduce or develop in mosquitoes can transmit several diseases, endanger human health, and overwhelm health systems. Synthetic pyrethroids are the most widely used insecticides against adult mosquitoes, but their widespread use has led to resistance. The adenosine triphosphate (ATP)-binding cassette (ABC) transporters are involved in the resistance monitoring of insects, but their role and underlying mechanisms in insecticide resistance have not been fully elucidated. In the present study, we identified ABC transporter genes in Culex pipiens and investigated their role in the development of insecticide resistance.

RESULTS

We identified 63 ABC transporter genes in Cx. pipiens and classified them as per the ABC transporter subfamilies. We also performed phylogenetic analysis. The knockdown rate of the mosquitoes orally fed with the ABC transporter inhibitor verapamil increased after deltamethrin treatment compared with that of the control group. Several genes from the ABCB, ABCC, and ABCG subfamilies were highly expressed in resistant mosquitoes. Immunofluorescence analysis revealed that ABCG6032427 was expressed in the head, chest, abdomen, wings, and legs, and the expression was the highest in the legs. Subsequently, knockdown of ABCG6032427 using RNA interference (RNAi) increased the sensitivity of the mosquitoes to deltamethrin, and scanning and transmission electron microscopy revealed that ABCG6032427 knockdown reduced cuticle thickness and the cuticle became loose and irregular.

CONCLUSIONS

ABCG6032427 may modulate cuticle thickness and structure, thus play an important role in the development of deltamethrin resistance in mosquitoes. Thus, it could be a potential target for deltamethrin resistance management in Cx. pipiens. © 2023 Society of Chemical Industry.

Inhibition Mechanism of Lactiplantibacillus plantarum on the Growth and Biogenic Amine Production in Morganella morganii

Morganella morganii, a spoilage bacterium in fermented foods, produces harmful biogenic amines (BAs). Although Lactiplantibacillus plantarum is widely used to inhibit spoilage bacteria, the inhibition pattern and inhibition mechanism of M. morganii by Lpb. plantarum are not well studied. In this study, we analysed the effects of the addition of Lpb. plantarum cell-free supernatant (CFS) on the growth and BA accumulation of M. morganii and revealed the mechanisms of changes in different BAs by using RNA sequencing transcriptome analysis. The results showed that Lpb. plantarum CFS could significantly inhibit M. morganii BAs in a weak acid environment (pH 6), and the main changes were related to metabolism. Carbohydrate and energy metabolism were significantly down-regulated, indicating that Lpb. plantarum CFS inhibited the growth activity and decreased the BA content of M. morganii. In addition, the change in histamine content is also related to the metabolism of its precursor amino acids, the change in putrescine content may also be related to the decrease in precursor amino acid synthesis and amino acid transporter, and the decrease in cadaverine content may also be related to the decrease in the cadaverine transporter. The results of this study help to inhibit the accumulation of harmful metabolites in fermented foods.

A microRNA, PC-5p-30_205949, regulates triflumezopyrim susceptibility in Laodelphax striatellus (Fallén) by targeting CYP419A1 and ABCG23

MicroRNAs (miRNAs) are known to be important post-transcriptional regulators of gene expression and have been shown to be associated with insecticide resistance in insects. In this research, we show that a miRNA, PC-5p-30_205949, is involved in triflumezopyrim susceptibility via regulating expressive abundance of cytochrome P450 CYP419A1 and ATP-binding cassette transporters ABCG23 in the small brown planthopper (SBPH), Laodelphax striatellus (Fallén). Triflumezopyrim treatment significantly reduced the abundance of PC-5p-30_205949, feeding of agomir-PC-5p-30_205949 significantly increased the sensitivity of SBPH to triflumezopyrim, and its spatiotemporal expression profiles showed that PC-5p-30_205949 were expressed at all developmental stages and were highly expressed in head tissue. By software prediction and dual luciferase reporter assay, the target genes of PC-5p-30_205949 were identified as two detoxification metabolism genes CYP419A1 and ABCG23. The relative expressions of CYP419A1 and ABCG23 were significantly up-regulated after 24 h, 48 h and 72 h with triflumezopyrim exposure. CYP419A1 was highly expressed in the 4th-instar nymphs and male adults, with the highest expression level in fat body. ABCG23 was highly expressed in female adults, and had the highest expression in head. Furthermore, silencing of CYP419A1 and ABCG23 by RNA interference significantly increased the mortality of SBPH to triflumezopyrim, and molecular docking showed that CYP419A1 and ABCG23 could stably bind to triflumezopyrim with binding free energies of -171.5622 and - 103.3402 kcal mol^-1, respectively. These results suggest that SBPH has a strategy to enhance the resistance to triflumezopyrim by attenuating the expression of PC-5P-30_205949, thereby activating the detoxification metabolic pathway by targeting CYP419A1 and ABCG23.

In Vitro and In Vivo Validation of CYP6A14 and CYP6N6 Participation in Deltamethrin Metabolic Resistance in Aedes albopictus

The extensive use of chemical insecticides for public health and agricultural purposes has increased the occurrence and development of insecticide resistance. This study used transcriptome sequencing to screen 10 upregulated metabolic detoxification enzyme genes from Aedes albopictus resistant strains. Of these, CYP6A14 and CYP6N6 were found to be substantially overexpressed in the deltamethrin-induced expression test, indicating their role in deltamethrin resistance in Ae. albopictus. Furthermore, the corresponding 60-kDa recombinant proteins, CYP6A14 and CYP6N6, were successfully expressed using the Escherichia coli expression system. Enzyme activity studies revealed that CYP6A14 (5.84 U/L) and CYP6N6 (6.3 U/L) have cytochrome P450 (CYP450) enzyme activity. In vitro, the metabolic analysis revealed that the recombinant proteins degraded deltamethrin into 1-oleoyl-sn-glycero-3-phosphoethanolamine and 2',2'-dibromo-2'-deoxyguanosine. Subsequently, the CYP450 genes in larvae of Ae. albopictus were silenced by RNA interference technology to study deltamethrin resistance in vivo. The silencing of CYP6A14 and CYP6N6 increased the mortality rate of mosquitoes without affecting their survival time, spawning quantity, hatching rate, and other normal life activities. Altogether, CYP6A14 and CYP6N6 belong to the CYP6 family and mutually increase deltamethrin resistance in Ae. albopictus.

The Transcriptomic Response of the Boll Weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), following Exposure to the Organophosphate Insecticide Malathion

Insecticide tolerance and resistance have evolved countless times in insect systems. Molecular drivers of resistance include mutations in the insecticide target site and/or gene duplication, and increased gene expression of detoxification enzymes. The boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is a pest of commercial cotton and has developed resistance in the field to several insecticides; however, the current organophosphate insecticide, malathion, used by USA eradication programs remains effective despite its long-term use. Here, we present findings from an RNA-seq experiment documenting gene expression post-exposure to field-relevant concentrations of malathion, which was used to provide insight on the boll weevil's continued susceptibility to this insecticide. Additionally, we incorporated a large collection of boll weevil whole-genome resequencing data from nearly 200 individuals collected from three geographically distinct areas to determine SNP allele frequency of the malathion target site, as a proxy for directional selection in response to malathion exposure. No evidence was found in the gene expression data or SNP data consistent with a mechanism of enhanced tolerance or resistance adaptation to malathion in the boll weevil. Although this suggests continued effectiveness of malathion in the field, we identified important temporal and qualitative differences in gene expression between weevils exposed to two different concentrations of malathion. We also identified several tandem isoforms of the detoxifying esterase B1 and glutathione S-transferases, which are putatively associated with organophosphate resistance.

High-Resolution Genetic Mapping Combined with Transcriptome Profiling Reveals That Both Target-Site Resistance and Increased Detoxification Confer Resistance to the Pyrethroid Bifenthrin in the Spider Mite Tetranychus urticae

Pyrethroids are widely applied insecticides in agriculture, but their frequent use has provoked many cases of resistance, in which mutations in the voltage-gated sodium channel (VGSC), the pyrethroid target-site, were shown to play a major role. However, for the spider mite Tetranychus urticae, it has also been shown that increased detoxification contributes to resistance against the pyrethroid bifenthrin. Here, we performed QTL-mapping to identify the genomic loci underlying bifenthrin resistance in T. urticae. Two loci on chromosome 1 were identified, with the VGSC gene being located near the second QTL and harboring the well-known L1024V mutation. In addition, the presence of an L925M mutation in the VGSC of a highly bifenthrin-resistant strain and its loss in its derived, susceptible, inbred line indicated the importance of target-site mutations in bifenthrin resistance. Further, RNAseq experiments revealed that genes encoding detoxification enzymes, including carboxyl/choline esterases (CCEs), cytochrome P450 monooxygenases and UDP-glycosyl transferases (UGTs), were overexpressed in resistant strains. Toxicity bioassays with bifenthrin (ester pyrethroid) and etofenprox (non-ester pyrethroid) also indicated a possible role for CCEs in bifenthrin resistance. A selection of CCEs and UGTs were therefore functionally expressed, and CCEinc18 was shown to metabolize bifenthrin, while teturUGT10 could glycosylate bifenthrin-alcohol. To conclude, our findings suggest that both target-site and metabolic mechanisms underlie bifenthrin resistance in T. urticae, and these might synergize high levels of resistance.

Functional characterization of ABC transporters mediates multiple neonicotinoid resistance in a field population of Aphis gossypii Glover

The ATP-binding cassette (ABC) transporters C and G subfamilies have been reported to be involved in insecticide detoxification, with most studies showing increased gene transcript levels in response to insecticide exposure. Our previous studies have suggested that ABCC and G transporters participate in cyantraniliprole and thiamethoxam resistance of Aphis gossypii. In this study, we focused on the potential roles of the ABCC and G transporters of an A. gossypii field population (SDR) in neonicotinoid detoxification. The results of leaf dip bioassays showed 629.17- and 346.82-fold greater resistance to thiamethoxam and imidacloprid in the SDR strain, respectively, than in the susceptible strain (SS). Verapamil, an ABC inhibitor, was used for synergism bioassays, and the results showed synergistic effects with thiamethoxam, with synergistic ratios (SRs) of 2.07 and 6.68 in the SS and SDR strains, respectively. In addition to thiamethoxam, verapamil increased imidacloprid toxicity by 1.68- and 1.62-fold in the SS and SDR strains respectively. Then, the expression levels of several ABCC and G transporters were analyzed in different treatments. We found that the transcript levels of AgABCG4, AgABCG17, AgABCG26, AgMRP8 and AgMRP12 were higher in the SDR strain than in the SS strain. The mRNA expression of AgABCG4, AgABCG7, AgABCG13, AgABCG17, AgABCG26, AgMRP8 and AgMRP12 in the SDR strain was increased after thiamethoxam and imidacloprid exposure. The results of transgenic Drosophila melanogaster bioassays suggested that overexpression of AgABCG4, AgABCG7, AgABCG13, AgABCG17, AgABCG26, AgMRP8 and AgMRP12 in transgenic flies was sufficient to confer thiamethoxam and imidacloprid resistance, and AgABCG4, AgABCG7, AgABCG13, AgABCG26 and AgMRP12 may be related to α-cypermethrin cross-resistance with weak effects. In addition, the knockdown of AgABCG4, AgABCG13, AgABCG26, AgMRP8 and AgMRP12, and the knockdown of AgABCG7 and AgABCG26 increased thiamethoxam and imidacloprid mortality in the SDR strain, respectively. Our results suggest that changes in the expression levels of ABCC and G transporters may contribute to neonicotinoid detoxification in the SDR strain, and provide a foundation for clarify the potential roles of ABCC and G transporters in insecticide resistance.

Transcriptional response and functional analysis of ATP-binding cassette transporters to tannic acid in pea aphid, Acyrthosiphon pisum (Harris)

Although tannins are widely distributed in broad beans and alfalfa, the pea aphid (Acyrthosiphon pisum) can still destroy them. The ATP binding cassette (ABC) transporters participate in the metabolism of plant secondary metabolites and pesticides in insects. However, whether ABC transporter genes play a role in the metabolism of tannins in the pea aphid is unclear. Here, we found that verapamil (an ABC transporter inhibitor) significantly increased the mortality of tannic acid to pea aphid, which indicated that ABC transporter gene was related to the metabolism of tannic acid by pea aphid. Then, we identified 54 putative ABC transporter genes from the genome database of A. pisum. These genes were divided into eight subfamilies, ApABCA to ApABCH, of which subfamily G has the largest number of genes with 19, followed by the subfamily C with 14. RT-qPCR results show that the expression levels of ApABCA2, ApABCC7, ApABCG2, and ApABCG3 were highly expressed in the first instar, while those of ApABCA3, ApABCG6, ApABCG7, ApABCH3, and ApABCH4 were highly expressed in adults. Furthermore, transcription levels of many ABC transporter genes were induced by tannic acid. Especially, ApABCG17 and ApABCH2 were obviously induced after being exposed to tannic acid. Meanwhile, knockdown of ApABCG17 by RNA interference resulted in increased sensitivity of pea aphid to tannic acid. These results suggest that ApABCG17 may be involved in tannic acid metabolism in pea aphid. This study will help us to understand the mechanism of tannic acid metabolism in pea aphid, and provides a basis for further research on the physiological function of ABC transporter genes in pea aphid.

Comparative genomic analysis of ABC transporter genes in Tenebrio molitor and four other tenebrionid beetles (Coleoptera: Tenebrionidea)

ATP-binding cassette (ABC) transporters, one of the largest transmembrane protein families, transport a diverse number of substate across membranes. Details of their diverse physiological functions have not been established. Here, we identified 87 ABC transporter genes in the genomes of Tenebrio molitor along with those from Asbolus verrucosus (104), Hycleus cichorii (65), and Hycleus phaleratus (80). Combining these genes (336 in total) with genes reported in Tribolium castaneum (73), we analyzed the phylogeny of ABC transporter genes in all five Tenebrionids. They are assigned into eight subfamilies (ABCA-H). In comparison to other species, the ABCC subfamily in this group of beetles appears expanded. The expression profiles of the T. molitor genes at different life stages and in various tissues were also investigated using transcriptomic analysis. Most of them display developmental specific expression patterns, suggesting to us their possible roles in development. Most of them are highly expressed in detoxification-related tissues including gut and Malpighian tubule, from which we infer their roles in insecticide resistance. We detected specific or abundant expressions of many ABC transporter genes in various tissues such as salivary gland, ovary, testis, and antenna. This new information helps generate new hypotheses on their biological significance within tissues.

Novel-miR-310 mediated response mechanism to Cry1Ac protoxin in Plutella xylostella (L.)

The diamondback moth (DBM), Plutella xylostella (L.), has evolved resistance to multiple insecticides including Bacillus thuringiensis (Bt). ATP-binding cassette (ABC) transporters are a class of transmembrane protein families, involved in multiple physiological processes and pesticide resistances in insects. However, the role and regulatory mechanism of ABC transporter in mediating the response to Bt Cry1Ac toxin remain unclear. Here, we characterized a MAPK signaling pathway-enriched ABCG subfamily gene PxABCG20 from DBM, and found it was differentially expressed in the Cry1Ac-resistant and Cry1Ac-susceptible strains. RNAi knockdown of PxABCG20 increased the tolerance of DBM to Cry1Ac protoxin. To explore the regulatory mechanism of PxABCG20 expression, we predicted the potential miRNAs targeting PxABCG20 using two target prediction algorithms. Luciferase reporter assay confirmed that novel-miR-310 was able to down-regulate PxABCG20 expression in HEK293T cells. Furthermore, injection of novel-miR-310 agomir markedly inhibited PxABCG20 expression, resulting in increased tolerance to Cry1Ac protoxin in susceptible strain, while injection of novel-miR-310 antagomir markedly induced the expression of PxABCG20, leading to decreased tolerance to Cry1Ac protoxin. Our work provides theoretical basis for exploring novel targets for the DBM response to Cry1Ac toxin and expands the understanding of miRNA role in mediating the susceptibility of insect pest to Cry1Ac toxin.

Identification of two ABCC transporters involved in malathion detoxification in the red flour beetle, Tribolium castaneum

ABC transporters have been suggested to be involved in insecticide detoxification in different insect species mainly based on the indirect observation of transcriptional upregulation of ABC gene expression in response to insecticide exposure. Previous studies performed by us and others in the red flour beetle, Tribolium castaneum, have analyzed the function of TcABCA-C and TcABCG-H genes using RNA interference (RNAi) and demonstrated that specific TcABCA and TcABCC genes are involved in the elimination of the pyrethroid tefluthrin and the benzoylurea diflubenzuron, because gene silencing increased the beetle's susceptibility to the insecticides. In this study, we focused on the potential functions of TcABCA-C genes in detoxification of the pyrethroid cyfluthrin (CF), the organophosphate malathion (MAL) and the diacylhdyazine tebufenozide (TBF). Analysis of transcript levels of selected TcABCA-C genes in response to treatment with these three chemically unrelated insecticides revealed that some genes were particularly upregulated after insecticide treatment. In addition, the ABC inhibitor verapamil synergized significantly the toxicity of MAL but only negligibly CF and TBF toxicities. Finally, silencing of two TcABCC genes by RNAi revealed a significant increase in susceptibility to MAL. In contrast, we did not observe a significant increase in insecticide-induced mortalities when knocking down TcABC genes in larvae treated with CF or TBF, although they were upregulated in response to insecticide treatment. Our results suggest that two pleiotropic ABCC transporters expressed in metabolic and excretory tissues contribute to the elimination of MAL.

Functional analysis of cyantraniliprole tolerance ability mediated by ATP-binding cassette transporters in Aphis gossypii glover

Cyantraniliprole, a second-generation anthranilic diamide insecticide, is widely used to control chewing and sucking pests. ATP-binding cassette transporters (ABCs) are a ubiquitous family of membrane proteins that play important roles in insect detoxification mechanisms. However, the potential effects of ABCs on cyantraniliprole-resistance remain unclear. In the present study, synergism bioassays revealed that verapamil, an ABC inhibitor, increased the toxicity of cyantraniliprole by 2.00- and 12.25-fold in the susceptible and cyantraniliprole-resistant strains of Aphis gossypii. Based on transcriptome data, the expression levels of ABCB4, ABCB5, ABCD1, ABCG4, ABCG7, ABCG13, ABCG16, ABCG17, ABCG26 and MRP12 were upregulated 1.56-, 1.32-, 1.51-, 2.03-, 1.65-, 1.50-, 4.18-, 6.07-, 4.68- and 4.69-fold, respectively, in the cyantraniliprole-resistant strain (CyR) compared to the susceptible strain (SS), as determined using RT-qPCR. Drosophila melanogaster ectopically overexpressing ABCB5, ABCG4, ABCG7, ABCG16, ABCG17, ABCG26 and MRP12 exhibited significantly increased tolerance to cyantraniliprole by 11.71-, 2.39-, 4.85-, 2.06-, 3.75-, 4.20- and 3.50-fold, respectively, with ABCB5 and ABCG family members being the most effective. Furthermore, the suppression of ABCB5, ABCG4, ABCG7, ABCG16, ABCG17, ABCG26 and MRP12 significantly increased the sensitivity of the CyR strain to cyantraniliprole. These results indicate that ABCs may play crucial roles in cyantraniliprole resistance and may provide information for shaping resistance management strategies.

Identification and Validation of ATP-Binding Cassette Transporters Involved in the Detoxification of Abamectin in Rice Stem Borer, Chilo suppressalis

Chilo suppressalis has developed high levels of resistance to abamectin in many areas of China, while the underline resistance mechanisms are largely unclear. ATP-binding cassette (ABC) transporters function in transporting a large diversity of substrates including insecticides and play important roles in the detoxification metabolism of insects. In this study, synergism bioassay revealed that the ABC transporters were involved in the detoxification of C. suppressalis to abamectin. Six ABC transporter genes were upregulated in C. suppressalis after abamectin exposure, among which five genes CsABCC8, CsABCE1, CsABCF1, CsABCF2, and CsABCH1 were induced in the detoxification-related tissues. In addition, the five ABC transporters were recombinantly expressed in Sf9 cells, and the cytotoxicity assay showed that the viabilities of cells expressing CsABCC8 or CsABCH1 were significantly increased when compared with the viabilities of cells expressing EGFP after abamectin, chlorantraniliprole, cyantraniliprole, fipronil, and chlorpyrifos treatment, respectively. Overexpression of CsABCE1 significantly increased the viabilities of cells to abamectin, chlorantraniliprole, deltamethrin, and indoxacarb exposure, respectively. These results suggested that CsABCC8, CsABCE1, and CsABCH1 might participate in the detoxification and transport of abamectin and several other classes of insecticides in C. suppressalis. Our study provides valuable insights into the transport-related detoxification mechanisms in C. suppressalis and other insects.

A near-chromosome level genome assembly of the European hoverfly, Sphaerophoria rueppellii (Diptera: Syrphidae), provides comparative insights into insecticide resistance-related gene family evolution

BACKGROUND

Sphaerophoria rueppellii, a European species of hoverfly, is a highly effective beneficial predator of hemipteran crop pests including aphids, thrips and coleopteran/lepidopteran larvae in integrated pest management (IPM) programmes. It is also a key pollinator of a wide variety of important agricultural crops. No genomic information is currently available for S. rueppellii. Without genomic information for such beneficial predator species, we are unable to perform comparative analyses of insecticide target-sites and genes encoding metabolic enzymes potentially responsible for insecticide resistance, between crop pests and their predators. These metabolic mechanisms include several gene families - cytochrome P450 monooxygenases (P450s), ATP binding cassette transporters (ABCs), glutathione-S-transferases (GSTs), UDP-glycosyltransferases (UGTs) and carboxyl/choline esterases (CCEs).

METHODS AND FINDINGS

In this study, a high-quality near-chromosome level de novo genome assembly (as well as a mitochondrial genome assembly) for S. rueppellii has been generated using a hybrid approach with PacBio long-read and Illumina short-read data, followed by super scaffolding using Hi-C data. The final assembly achieved a scaffold N50 of 87Mb, a total genome size of 537.6Mb and a level of completeness of 96% using a set of 1,658 core insect genes present as full-length genes. The assembly was annotated with 14,249 protein-coding genes. Comparative analysis revealed gene expansions of CYP6Zx P450s, epsilon-class GSTs, dietary CCEs and multiple UGT families (UGT37/302/308/430/431). Conversely, ABCs, delta-class GSTs and non-CYP6Zx P450s showed limited expansion. Differences were seen in the distributions of resistance-associated gene families across subfamilies between S. rueppellii and some hemipteran crop pests. Additionally, S. rueppellii had larger numbers of detoxification genes than other pollinator species.

CONCLUSION AND SIGNIFICANCE

This assembly is the first published genome for a predatory member of the Syrphidae family and will serve as a useful resource for further research into selectivity and potential tolerance of insecticides by beneficial predators. Furthermore, the expansion of some gene families often linked to insecticide resistance and selectivity may be an indicator of the capacity of this predator to detoxify IPM selective insecticides. These findings could be exploited by targeted insecticide screens and functional studies to increase effectiveness of IPM strategies, which aim to increase crop yields by sustainably and effectively controlling pests without impacting beneficial predator populations.

Comprehensive Detoxification Mechanism Assessment of Red Imported Fire Ant (Solenopsis invicta) against Indoxacarb

The red imported fire ant (Solenopsis invicta) is one of the deadliest invasive ant species that threatens the world by disrupting biodiversity, important functions within a natural ecosystem, and community structure. They are responsible for huge economic losses in the infested countries every year. Synthetic insecticides, especially indoxacarb, have been broadly used to control S. invicta for many years. However, the biochemical response of S. invicta to indoxacarb remains largely undiscovered. Here, we used the sublethal doses of indoxacarb on the S. invicta collected from the eight different cities of Southern China. The alteration in the transcriptome profile of S. invicta following sublethal dosages of indoxacarb was characterized using high-throughput RNA-seq technology. We created 2 libraries, with 50.93 million and 47.44 million clean reads for indoxacarb treatment and control, respectively. A total of 2018 unigenes were regulated after insecticide treatment. Results indicated that a total of 158 differentially expressed genes (DEGs) were identified in the indoxacarb-treated group, of which 100 were significantly upregulated and 58 were downregulated, mostly belonging to the detoxification enzymes, such as AChE, CarE, and GSTs. Furthermore, results showed that most of these DEGs were found in several KEGG pathways, including steroid biosynthesis, other drug metabolizing enzymes, glycerolipid metabolism, chemical carcinogenesis, drug-metabolizing cytochrome P450, glutathione metabolism, glycerophospholipid metabolism, glycolysis/gluconeogenesis, and metabolism of xenobiotics. Together, these findings indicated that indoxacarb causes significant alteration in the transcriptome profile and signaling pathways of S. invicta, providing a foundation for further molecular inquiry.

Comparative analysis of the detoxification gene inventory of four major Spodoptera pest species in response to xenobiotics

The genus Spodoptera (Lepidoptera: Noctuidae) comprises some of the most polyphagous and destructive agricultural pests worldwide. The success of many species of this genus is due to their striking abilities to adapt to a broad range of host plants. Superfamilies of detoxification genes play a crucial role in the adaption to overcome plant defense mechanisms mediated by numerous secondary metabolites and toxins. Over the past decade, a substantial amount of expression data in Spodoptera larvae was produced for those genes in response to xenobiotics such as plant secondary metabolites, but also insecticide exposure. However, this information is scattered throughout the literature and in most cases does not allow to clearly identify candidate genes involved in host-plant adaptation and insecticide resistance. In the present review, we analyzed and compiled information on close to 600 pairs of inducers (xenobiotics) and induced genes from four main Spodoptera species: S. exigua, S. frugiperda, S. littoralis and S. litura. The cytochrome P450 monooxygenases (P450s; encoded by CYP genes) were the most upregulated detoxification genes across the literature for all four species. Most of the data was provided from studies on S. litura, followed by S. exigua, S. frugiperda and S. littoralis. We examined whether these detoxification genes were reported for larval survival under xenobiotic challenge in forward and reverse genetic studies. We further analyzed whether biochemical assays were carried out showing the ability of corresponding enzymes and transporters to breakdown and excrete xenobiotics, respectively. This revealed a clear disparity between species and the lack of genetic and biochemical information in S. frugiperda. Finally, we discussed the biological importance of detoxification genes for this genus and propose a workflow to study the involvement of these enzymes in an ecological and agricultural context.

Genome-wide analyses of ATP-Binding Cassette (ABC) transporter gene family and its expression profile related to deltamethrin tolerance in non-biting midge Propsilocerus akamusi

Non-biting midges are dominant species in aquatic systems and often used for studying the toxicological researches of insecticides. ATP-binding cassette (ABC) transporters represent the largest known members in detoxification genes but is little known about their function in non-biting midges. Here, we selected Propsilocerus akamusi, widespread in urban streams, to first uncover the gene structure, location, characteristics, and phylogenetics of chironomid ABC transporters at genome-scale. Fifty-seven ABC transporter genes are located on four chromosomes, including eight subfamilies (ABCA-H). The ABCC, ABCG, and ABCH subfamilies experienced the duplication events to different degrees. The study showed that expression of the PaABCG17 gene is uniquely significantly elevated, with deltamethrin concentration increasing (1, 4, and 20 ug/L) both in RNA-seq and qPCR results. Additionally, the ABC transporter members of other six chironomids with assembled genomes are first described and used to investigate the characteristic of those living in the different adverse habitats. The ABC transporter frame for Propsilocerus akamusi and its transcriptomic results lay an important foundation for providing valuable resources for understanding the ABC transporter function in insecticide toxification of this species as well as those of other non-biting midges. The PaABCG17 gene is shown to play an important role in deltamethrin detoxification, and it functions need to be further investigated and might be used in the management of insecticide-resistance in chironomid adults.

Delineating the Role of Aedes aegypti ABC Transporter Gene Family during Mosquito Development and Arboviral Infection via Transcriptome Analyses

Aedes aegypti acts as a vector for several arboviral diseases that impose a major socio-economic burden. Moreover, the absence of a vaccine against these diseases and drug resistance in mosquitoes necessitates the development of new control strategies for vector-borne diseases. ABC transporters that play a vital role in immunity and other cellular processes in different organisms may act as non-canonical immune molecules against arboviruses, however, their role in mosquito immunity remains unexplored. This study comprehensively analyzed various genetic features of putative ABC transporters and classified them into A-H subfamilies based on their evolutionary relationships. Existing RNA-sequencing data analysis indicated higher expression of cytosolic ABC transporter genes (E & F Subfamily) throughout the mosquito development, while members of other subfamilies exhibited tissue and time-specific expression. Furthermore, comparative gene expression analysis from the microarray dataset of mosquito infected with dengue, yellow fever and West Nile viruses revealed 31 commonly expressed ABC transporters suggesting a potentially conserved transcriptomic signature of arboviral infection. Among these, only a few transporters of ABCA, ABCC and ABCF subfamily were upregulated, while most were downregulated. This indicates the possible involvement of ABC transporters in mosquito immunity.

Identification of ABCG transporter genes associated with chlorantraniliprole resistance in Plutella xylostella (L.)

BACKGROUND

Plutella xylostella (L.) is a serious worldwide pest that feeds on cruciferous plants and has evolved resistance to different classes of insecticides used for its control, including chlorantraniliprole. ATP-binding cassette (ABC) transporters, constituting the largest transport family in organisms, are involved in phase III of the detoxification process and may play important roles in insecticide resistance.

RESULTS

A total of 15 ABC transporter transcripts from subfamily G were identified in P. xylostella based on the latest DBM genome. Synergism studies showed that treatment with verapamil, a potent inhibitor of ABC transporters, significantly increased the toxicity of chlorantraniliprole against larvae of two chlorantraniliprole-resistant P. xylostella populations (NIL and BL). ABCG2, ABCG5, ABCG6, ABCG9, ABCG11, ABCG14 and ABCG15 were significantly overexpressed in NIL and BL compared with the susceptible population (SS), and ABCG1, ABCG6, ABCG8, ABCG9, ABCG14 and ABCG15 were significantly upregulated after treatment with the LC₅₀ of chlorantraniliprole in SS. Subsequently, ABCG6, ABCG9 and ABCG14, which were overexpressed in both NIL and BL and could be induced in SS, were chosen for functional study. RNAi-mediated knockdown of each of the three ABCGs significantly increased the sensitivity of larvae to chlorantraniliprole. These results confirmed that overexpression of ABCG6, ABCG9 and ABCG14 may contribute to chlorantraniliprole resistance in P. xylostella.

CONCLUSION

Overexpression of some genes in the ABCG subfamily is involved in P. xylostella resistance to chlorantraniliprole. These results may help to establish a foundation for further studies investigating the role played by ABC transporters in chlorantraniliprole resistance in P. xylostella or other insect pests. © 2021 Society of Chemical Industry.

Functional analysis of ABCG and ABCH transporters from the red flour beetle, Tribolium castaneum

BACKGROUND

ATP-binding cassette transporter (ABC transporter) subfamilies ABCA-C and ABCG-H have been implicated in insecticide detoxification, mostly based on findings of elevated gene expression in response to insecticide treatment. We previously characterized TcABCA-C genes from the model beetle and pest Tribolium castaneum and demonstrated that TcABCA and TcABCC genes are involved in the elimination of diflubenzuron, because RNA interference (RNAi)-mediated gene silencing increased susceptibility. In this study, we focused on the potential functions of TcABCG and TcABCH genes in insecticide detoxification.

RESULTS

When we silenced the expression of TcABCG-H genes using RNAi, we noticed a previously unreported developmental RNAi phenotype for TcABCG-4F, which is characterized by 50% mortality and ecdysial arrest during adult moult. When we knocked down the Drosophila brown orthologue TcABCG-XC, we did not obtain apparent eye colour phenotypes but did observe a loss of riboflavin uptake by Malpighian tubules. Next, we determined the expression profiles of all TcABCG-H genes in different tissues and developmental stages and analysed transcript levels in response to treatment with four chemically unrelated insecticides. We found that some genes were specifically upregulated after insecticide treatment. However, when we determined insecticide-induced mortalities in larvae that were treated by double-stranded RNA injection to silence those TcABCG-H genes that were upregulated, we did not observe a significant increase in susceptibility to insecticides.

CONCLUSION

Our findings suggest that the observed insecticide-dependent induction of TcABCG-H gene expression reflects an unspecific stress response, and hence underlines the significance of functional studies on insecticide detoxification. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Identification and Expression Characterization of ATP-Binding Cassette (ABC) Transporter Genes in Melon Fly

Simple Summary

The melon fly, Zeugodacus cucurbitae, is an important agricultural pest. At present, chemical pesticide treatment is the main method for field control, but this promotes pesticide resistance by Z. cucurbitae, because of its frequent use. ABC transporters are involved in detoxification metabolism, but few studies have yet considered their expression in melon fly. In this study, we identified the ABC transporters genes at a genome-wide level in melon fly, and analysed their spatiotemporal expression patterns, as well as changes in expression after insecticides treatments. A total of 49 ABC transporters were identified, and their expression levels varied at different developmental stages and between tissues. After three insecticides treatment, ZcABCB7 and ZcABCC2 were up-regulated. After β-cypermethrin induction, tissues were dissected at 12, 24 and 48 h, and the expression levels of a number of ABC genes were highly expressed within the fat body. From these results, we conclude that ZcABCB7 and ZcABCC2 may be involved in detoxification metabolism, and that the fat body is the main tissue that plays this role.

Abstract

The ATP-binding cassette (ABC) transporter is a protein superfamily that transports specific substrate molecules across lipid membranes in all living species. In insects, ABC transporter is one of the major transmembrane protein families involved in the development of xenobiotic resistance. Here, we report 49 ABC transporter genes divided into eight subfamilies (ABCA-ABCH), including seven ABCAs, seven ABCBs, 10 ABCCs, two ABCDs, one ABCE, three ABCFs, 16 ABCGs, and three ABCHs according to phylogenetic analysis in Zeugodacus cucurbitae, a highly destructive insect pest of cucurbitaceous and other related crops. The expressions level of 49 ABC transporters throughout various developmental stages and within different tissues were evaluated by quantitative transcriptomic analysis, and their expressions in response to three different insecticides were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). These ABC transporter genes were widely expressed at developmental stages but most highly expressed in tissues of the midgut, fat body and Malpighian tube. When challenged by exposure to three insecticides, abamectin, β-cypermethrin, and dinotefuran, the expressions of ZcABCB7 and ZcABCC2 were significantly up-regulated. ZcABCB1, ZcABCB6, ZcABCB7, ZcABCC2, ZcABCC3, ZcABCC4, ZcABCC5, and ZcABCC7 were significantly up-regulated in the fat body at 24 h after β-cypermethrin exposure. These data suggest that ZcABCB7 and ZcABCC2 might play key roles in xenobiotic metabolism in Z. cucurbitae. Collectively, these data provide a foundation for further analysis of ABCs in Z. cucurbitae.

Ursolic acid reduces Adriamycin resistance of human ovarian cancer cells through promoting the HuR translocation from cytoplasm to nucleus

Ursolic acid (UA) has been shown to suppress various tumor progression, however, its roles in Adriamycin resistance of human ovarian cancer (OC) cells are still unclear. This work aims to investigate the effects of UA on the Adriamycin resistance of human OC cells. Here, we constructed Adriamycin-resistant OC SKOV3-Adr cells and found that UA attenuated Adriamycin resistance in SKOV3-Adr cells. Additionally, UA enhanced Adriamycin sensitivity in the parental SKOV3 and another OC cell line A2780 cells. Mechanistic studies showed that HuR mRNA level was similar between SKOV3 and SKOV3-Adr cells, but the cytoplasmic expression of HuR protein was increased in SKOV3-Adr cells compared with that in SKOV3 cells, and subsequently enhancing the mRNA stability of multidrug resistance gene 1 (MDR1). Moreover, UA had no effects on HuR expression, but promoted the cytoplasm-nucleus translocation of HuR protein, decreased MDR1 mRNA stability and thus reduced MDR1 expression. Furthermore, overexpression of MDR1 rescued the effects of UA on Adriamycin resistance and sensitivity. This work reveals a novel HuR/MDR1 axis responsible for UA-mediated attenuation on Adriamycin resistance in OC cells.

Transcriptional Response of ATP-Binding Cassette (ABC) Transporters to Insecticide in the Brown Planthopper, Nilaparvata lugens (Stål)

The ATP-binding cassette (ABC) transporter superfamily is one of the largest groups of proteins and plays a non-negligible role in phase III of the detoxification process, which is highly involved in the response of insects to environmental stress (plant secondary metabolites and insecticides). In the present study, in Nilaparvata lugens, we identified 32 ABC transporters, which are grouped into eight subfamilies (ABCA–H) based on phylogenetic analysis. The temporal and spatial expression profiles suggested that the nymphal stages (1st–5th) and adult males showed similarity, which was different from eggs and adult females, and NlABCA1, NlABCA2, NlABCB6, NlABCD2, NlABCG4, NlABCG12, NlABCG15, and NlABCH1 were highly expressed in the midgut and Malpighian tubules. In addition, ABCG12, which belongs to the ABC transporter G subfamily, was significantly upregulated after exposure to sulfoxaflor, nitenpyram, clothianidin, etofenprox, chlorpyrifos, and isoprocarb. Moreover, verapamil significantly increased the sensitivity of N. lugens to nitenpyram, clothianidin, etofenprox, chlorpyrifos, and isoprocarb. These results provide a basis for further research on ABC transporters involved in detoxification in N. lugens, and for a more comprehensive understanding of the response of N. lugens to environmental stress.

Transcriptional plasticity of different ABC transporter genes from Tribolium castaneum contributes to diflubenzuron resistance

The development of insecticide resistance challenges the sustainability of pest control and several studies have shown that ABC transporters contribute to this process. ABC transporters are known to transport a large range of chemically diverse molecules across cellular membranes, and therefore the identification of ABC transporters involved in insecticide resistance is difficult. Here, we describe a comprehensive strategy for the identification of whole sets of ABC transporters involved in insecticide resistance using the pest beetle, Tribolium castaneum (Tc) as a model. We analyzed the expression of ABCA to ABCC genes in different tissues and developmental stages using larvae that were sensitive or resistant to diflubenzuron (DFB). The mRNA levels of several ABC genes expressed in excretory or metabolic tissues such as midgut, Malpighian tubules or fat body were markedly upregulated in response to DFB. Next, we monitored mortality in the presence of the ABC inhibitor verapamil, and found that it causes sensitization to DFB. We furthermore established a competitive assay for the elimination of DFB, based on Texas Red (TR) fluorescence. We monitored TR elimination in larvae that were treated with DFB or different ABC inhibitors, and combinations of them. TR elimination was decreased significantly in the presence of DFB, verapamil and the ABCC inhibitor MK-571. The effect was synergized when DFB and verapamil were both present suggesting that the transport of TR and DFB involves overlapping sets of ABC transporters. Finally, we silenced the expression of DFB-responding ABC genes by RNA interference and then followed the survival rates after DFB exposure. Mortality increased particularly when specific ABCA and ABCC genes were silenced. Taken together, we were able to show that different ABC transporters expressed in metabolic and excretory tissues contribute to the elimination of DFB. Up- or down-regulation of gene expression occurs within a few days already at very low DFB concentrations. These results suggests that transcriptional plasticity of several ABC genes allows adaptation of the efflux capacity in different tissues to eliminate insecticides and/or their metabolites.

Prognostic significance and molecular mechanisms of adenosine triphosphate-binding cassette subfamily C members in gastric cancer

Gastric cancer (GC) is one of the major leading causes of tumor-related deaths worldwide. Adenosine triphosphate-binding cassette subfamily C (ABCC) consists of 13 members, ABCC1 to 13, which were examined for their associations with GC.The online Kaplan-Meier Plotter database was used to determine the prognostic significance of ABCC subfamily members in GC. Stratified analyses were performed using gender, disease stage, degree of tumor differentiation, expression of human epidermal growth factor receptor 2 (HER2), and Lauren classification. Molecular mechanisms were examined using the database for annotation, visualization, and integrated discovery database.ABCC1, ABCC3, ABCC7, ABCC8, ABCC9, and ABCC10 expression showed prognostic significance in the whole population and in male and female subpopulations (all P ≤ .05). Furthermore, high expression of most ABCC family members always suggested a poor prognosis, except for ABCC7 (P > .05). Stratified analyses revealed that ABCC1, ABCC3, ABCC7, ABCC8, ABCC9, and ABCC10 expression showed prognostic significance for the whole population, as well as male and female populations. ABCC2 and ABCC9 were significantly correlated with all disease stages, while ABCC2 and ABCC6 were significantly correlated with all Lauren classifications. Expression of ABCC1, ABCC3, ABCC5, ABCC7, ABCC8, ABCC9, and ABCC10 was significantly correlated with either negative or positive of HER2 status (all P ≤ .05). Enrichment analysis indicated that these genes were involved in ATPase activity, transmembrane transport, or were ABC transporters (all P ≤ .05).ABCC1, ABCC3, ABCC7, ABCC8, ABCC9, and ABCC10 may be potential prognosis biomarkers for GC, acting as ABC transporters and via ATPase activity.

Effects of Insecticide Stress on Expression of NlABCG Transporter Gene in the Brown Planthopper, Nilaparvata lugens

The brown planthopper (BPH), Nilaparvata lugens, is an important pest of rice that severely affects production. Insecticides are an important means of controlling BPH, but their long-term use has led to resistance. To provide insight into BPH responses to insecticide stress, we determined the expression levels of BPH ABCG transporter genes under treatment with thiamethoxam, abamectin, and cyantraniliprole at LC₁₀, LC₂₅, LC₅₀, and LC₉₀. We cloned 13 BPH ABCG transporters, named NlABCG1 to NlABCG13. Conservative domain analysis showed that all 13 transporters have one nucleotide binding domain and one transmembrane domain, typical of semi-molecular transporters. Real-time quantitative PCR showed that thiamethoxam, abamectin, and cyantraniliprole stress increased the expression of some NlABCG transporters gene in BPH. However, after treatment with thiamethoxam at LC₂₅ and abamectin at LC₁₀, there was no significant upregulation of NlABCG. These results indicate that the expression of NlABCG varies in response to stress from different insecticides. These findings provide baseline information for further understanding of the molecular mechanisms of insecticide resistance in BPH.