Multiple ATP-binding cassette transporters genes are involved in thiamethoxam resistance in Aphis gossypii glover

Application of omics technology in ecotoxicology of arthropod in farmland

Arthropods, abundant in farmland, have unique biological traits that make them valuable for studying the ecotoxicological impacts of pollutants. Recent advancements in multi-omics technologies have enhanced their use in assessing pollution risks and understanding toxicity mechanisms. This article reviews recent developments in applying omics technologies-genomics, transcriptomics, proteomics, metabolomics, and meta-omics-to ecotoxicological research on farmland arthropods. Agricultural arthropods manage genes and proteins, such as metallothioneins, antioxidant enzyme systems, heat shock proteins, cytochrome P450, carboxylesterases, and glutathione S-transferases, for detoxification and antioxidant purposes. They adjust amino acid, sugar, and lipid metabolism to counteract pollutant-induced energy drain and modify gut microbiota to aid in detoxification. This study advocates for enhanced analysis of compound pollution and emerging pollutants using multi-omics, especially meta-omics, to clarify the toxicological mechanisms underlying arthropod responses to these pollutants. Furthermore, it underscores the urgent need for subsequent gene function mining and validation to support biological control strategies and promote sustainable agricultural practices. The findings of this research provide significant insights into the toxicological impacts and mechanisms of pollutants within farmland ecosystems, thereby contributing to the preservation of arthropod diversity.

The miRNA-275 Targeting RpABCG23L is Involved in Pyrethroid Resistance in the Bird Cherry-Oat Aphid, a Serious Agricultural Pest

Rhopalosiphum padi is a global agricultural pest which had developed resistance to different insecticides. The ATP-binding cassette (ABC) transporter plays an important role in insecticide resistance. However, ABC transporters' role and regulatory mechanism in mediating R. padi 's response to pyrethroids are unclear. In this study, we found that RpABCG23L was significantly overexpressed in the pyrethroid-resistant strains of R. padi. Knockdown of RpABCG23L significantly increased the susceptibility of R. padi to lambda-cyhalothrin and bifenthrin. Luciferase reporter gene analysis showed that miR-275 binds to the RpABCG23L coding region and down-regulates its expression. Injection of miR-275 mimics significantly reduced RpABCG23L expression and increased R. padi susceptibility to lambda-cyhalothrin and bifenthrin, while miR-275 inhibitor injection enhanced RpABCG23L expression and increased tolerance to both insecticides. The results provide a theoretical basis for understanding the mechanism of miRNA-mediated pyrethroid resistance, and open up a new way for the development of miRNA-based biopesticides.

Silencing OdfoP-gp1 and OdfoP-gp3 with dsRNA increased the lethality of the nonsteroidal ecdysone agonist RH-5849 against Odontotermes formosanus (Shiraki)

Odontotermes formosanus (Shiraki) is a highly damaging social insect that causes significant economic losses. Insect growth regulators (IGRs) are efficient and environmentally friendly insecticides. 1,2-dibenzoyl-1-tert-butylhydrazine (RH-5849), a nonsteroidal ecdysone agonist of IGR, is highly effective in controlling various insect species. In this study, the toxicity of RH-5849 against O. formosanus was assessed. To investigate whether ATP-binding cassette (ABC) transporter proteins, detoxification enzymes, play crucial roles in the defense of O. formosanus against RH-5849, transcriptome sequencing was conducted in O. formosanus. Through RNA sequencing, 27 ABC transporter protein genes were identified, 23 of which were significantly upregulated after O. formosanus was exposed to RH-5849, especially two P-glycoprotein genes, OdfoP-gp1 and OdfoP-gp3, whose expression levels were the most significantly upregulated, at 5.79 and 5.56, respectively. Furthermore, using dsRNAs to interfere with the expression of OdfoP-gp1 and OdfoP-gp3, we found that the maximum interference efficiency was achieved at 24 h, with efficiencies of 85.30 % and 59.59 %, respectively. Based on these findings, dsRNA was coupled with RH-5849, and the results indicated that the lethality of RH-5849 against O. formosanus significantly increased following dsRNA interference. Overall, the lethality of RH-5849 significantly increased following dsRNA interference, suggesting that ABC transporter proteins, especially P-glycoproteins, play a crucial role in the defense of O. formosanus against RH-5849. This study provides a new strategy for termite control through the combination of dsRNA and IGR.

The role of ATP-binding cassette transporters in arthropod pesticide toxicity and resistance

Pesticide resistance in arthropods threatens agricultural productivity and the control of vector-borne diseases. The ATP-binding cassette (ABC) transporters have emerged as important factors in the toxicity of synthetic pesticides, as well as for Bacillus thuringiensis insecticidal Cry protein binding. Depending on the localization of expression, both higher and lower expression of ABCs have been linked with pesticide resistance. The recent development of genetic-based approaches such as RNAi and CRISPR/Cas9 gene editing in nonmodel species, has greatly contributed to unveil their functional importance in pesticide toxicity and resistance. Using these tools, we are now poised to further unravel the molecular genetic mechanisms of gene regulation uncovering more elusive regulatory resistance genes.

Activation of CncC pathway by ROS burst regulates ABC transporter responsible for beta-cypermethrin resistance in Dermanyssus gallinae (Acari:Dermanyssidae)

The drug resistance of poultry red mites to chemical acaricides is a global issue in the control of the mites, which presents an ongoing threat to the poultry industry. Though the increased production of detoxification enzymes has been frequently implicated in resistance development, the overexpression mechanism of acaricide-resistant related genes in mites remains unclear. In the present study, it was observed that the transcription factor Cap 'n' Collar isoform-C (CncC) and its partner small muscle aponeurosis fibromatosis (Maf) were highly expressed in resistant strains compared to sensitive strains under the stress of beta-cypermethrin. When the CncC/Maf pathway genes were down-regulated by RNA interference (RNAi), the expression of the ABC transporter genes was down-regulated, leading to a significant increase in the sensitivity of resistant strains to beta-cypermethrin, suggesting that CncC/Maf played a crucial role in mediating the resistance of D.gallinae to beta-cypermethrin by regulating ABC transporters. Furthermore, it was observed that the content of H2O2 and the activities of peroxidase (POD) and catalase (CAT) enzymes were significantly higher in resistant strains after beta-cypermethrin stress, indicating that beta-cypermethrin activates reactive oxygen species (ROS). In ROS scavenger assays, it was found that the expression of CncC/Maf significantly decreased, along with a decrease in the ABC transporter genes. The present study showed that beta-cypermethrin seemed to trigger the outbreak of ROS, subsequently activated the CncC/Maf pathway, as a result induced the ABC transporter-mediated resistance to the drug, shedding more light on the resistance mechanisms of D.gallinae to pyrethroids.

Structural and functional insights into the ATP-binding cassette transporter family in the corn planthopper, Peregrinus maidis

The corn planthopper, Peregrinus maidis, is an economically important pest of maize and sorghum. Its feeding behaviour and the viruses it transmits can significantly reduce crop yield. The control of P. maidis and its associated viruses relies heavily on insecticides. However, control has proven difficult due to limited direct exposure of P. maidis to insecticides and rapid development of resistance. As such, alternative control methods are needed. In the absence of a genome assembly for this species, we first developed transcriptomic resources. Then, with the goal of finding targets for RNAi-based control, we identified members of the ATP-binding cassette transporter family and targeted specific members via RNAi. PmABCB_160306_3, PmABCE_118332_5 and PmABCF_24241_1, whose orthologs in other insects have proven important in development, were selected for knockdown. We found that RNAi-mediated silencing of PmABCB_160306_3 impeded ovary development; disruption of PmABCE_118332_5 resulted in localized melanization; and knockdown of PmABCE_118332_5 or PmABCF_24241_1 each led to high mortality within five days. Each phenotype is similar to that found when targeting the orthologous gene in other species and it demonstrates their potential for use in RNAi-based P. maidis control. The transcriptomic data and RNAi results presented here will no doubt assist with the development of new control methods for this pest.

Biochemical and Molecular Analysis of Field Resistance to Spirodiclofen in Panonychus citri (McGregor)

Spirodiclofen is one of the most widely used acaricides in China. The citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae), is one of the most destructive citrus pests worldwide and has developed a high resistance to spirodiclofen. However, the molecular mechanism of spirodiclofen resistance in P. citri is still unknown. In this study, we identified a field spirodiclofen-resistant strain (DL-SC) that showed 712-fold resistance to spirodiclofen by egg bioassay compared to the susceptible strain. Target-site resistance was not detected as non-synonymous mutations were not found by amplification and sequencing of the ACCase gene of resistant and susceptible strains; in addition, the mRNA expression levels of ACCase were similar in both resistant and susceptible strains. The activity of detoxifying enzymes P450s and CCEs in the resistant strain was significantly higher than in the susceptible strain. The transcriptome expression data showed 19 xenobiotic metabolisms genes that were upregulated. Stage-specific expression profiling revealed that the most prominent upregulated gene, CYP385C10, in transcriptome data was significantly higher in resistant strains in all stages. Furthermore, functional analysis by RNAi indicated that the mortality caused by spirodiclofen was significantly increased by silencing the P450 gene CYP385C10. The current results suggest that overexpression of the P450 gene, CYP385C10, may be involved in spirodiclofen resistance in P. citri.

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.

Functional Inquiry into ATP-Binding Cassette Transporter Genes Contributing to Spirotetramat Resistance in Aphis gossypii Glover

ATP-binding cassette (ABC) transporters regulate the efflux of a broad spectrum of substrates to extracellular transporting, which play an important role in the detoxification process in arthropods. Here, we described a comprehensive approach to explore the involvement of ABC transporters in spirotetramat resistance in cotton aphids. In this study, synergism bioassays showed 17.05% and 35.42% increases in the toxicity to spirotetramat with the ABC inhibitor verapamil in adult and 3rd instar nymph aphids of the SR strain, respectively. In a competitive assay based on the microinjection of a fluorescent ABC transporter substrate, verapamil (a general ABC inhibitor) and spirotetramat significantly inhibited the elimination of Texas Red. Based on transcriptome data of midguts of spirotetramat-susceptible (SS) and -resistant (SR) strains, the expression levels of ABCB4, ABCB5, ABCF2, MRP11, and MRP12 were significantly upregulated in the SR strain midgut compared to that of the SS strain. Gene functional analysis based on ectopic expression and RNA interference (RNAi) proved that ABCB4, ABCB5, ABCF2, MRP11, and MRP12 were involved in the tolerance of cotton aphids to spirotetramat. Moreover, the upregulated ABCF2, ABCB4, and ABCB5 in the midgut of the SR strain contributed more to the resistance of spirotetramat in in vitro functional analysis. In summary, these results demonstrate that candidate ABC transporter genes in the midgut tissue were involved in spirotetramat resistance, which will help reveal the relationship between ABC transporters and the development of spirotetramat resistance in field populations.

miRNA novel_268 targeting NlABCG3 is involved in nitenpyram and clothianidin resistance in Nilaparvata lugens

The brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most destructive pests that seriously threatens the high-quality and safe production of rice. However, due to the unscientific use of chemical insecticides, N. lugens has developed varying levels of resistance to insecticides, including nitenpyram and clothianidin. The ATP-binding cassette (ABC) transporter plays a nonnegligible role in phase III of the detoxification process, which may play an important role in insecticide resistance. In the present study, NlABCG3 was significantly overexpressed in both the NR and CR populations compared with susceptible populations. Silencing NlABCG3 significantly increased the susceptibility of BPH to nitenpyram and clothianidin. In addition, RNAi-mediated knockdown of three key genes in the miRNA biogenesis pathway altered the level of NlABCG3. Subsequently, the luciferase reporter assays demonstrated that novel_268 binds to the NlABCG3 coding region and downregulates its expression. Furthermore, injection of miRNA inhibitors or mimics of novel_268 significantly altered the susceptibility of N. lugens to nitenpyram and clothianidin. These results suggest that miRNA novel_268 targeting NlABCG3 is involved in nitenpyram and clothianidin resistance in N. lugens. These findings may help to enhance our knowledge of the transcriptional regulation of the ABC transporter that mediate insecticide resistance in N. lugens.

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.

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.

A scaffold-level genome assembly of a minute pirate bug, Orius laevigatus (Hemiptera: Anthocoridae), and a comparative analysis of insecticide resistance-related gene families with hemipteran crop pests

BACKGROUND

Orius laevigatus, a minute pirate bug, is a highly effective beneficial predator of crop pests including aphids, spider mites and thrips in integrated pest management (IPM) programmes. No genomic information is currently available for O. laevigatus, as is the case for the majority of beneficial predators which feed on crop pests. In contrast, genomic information for crop pests is far more readily available. The lack of publicly available genomes for beneficial predators to date has limited our ability to perform comparative analyses of genes encoding potential insecticide resistance mechanisms between crop pests and their predators. These mechanisms include several gene/protein families including cytochrome P450s (P450s), ATP binding cassette transporters (ABCs), glutathione S-transferases (GSTs), UDP-glucosyltransferases (UGTs) and carboxyl/cholinesterases (CCEs).

METHODS AND FINDINGS

In this study, a high-quality scaffold level de novo genome assembly for O. laevigatus has been generated using a hybrid approach with PacBio long-read and Illumina short-read data. The final assembly achieved a scaffold N50 of 125,649 bp and a total genome size of 150.98 Mb. The genome assembly achieved a level of completeness of 93.6% using a set of 1658 core insect genes present as full-length genes. Genome annotation identified 15,102 protein-coding genes - 87% of which were assigned a putative function. Comparative analyses revealed gene expansions of sigma class GSTs and CYP3 P450s. Conversely the UGT gene family showed limited expansion. Differences were seen in the distributions of resistance-associated gene families at the subfamily level between O. laevigatus and some of its targeted crop pests. A target site mutation in ryanodine receptors (I4790M, PxRyR) which has strong links to diamide resistance in crop pests and had previously only been identified in lepidopteran species was found to also be present in hemipteran species, including O. laevigatus.

CONCLUSION AND SIGNIFICANCE

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

Identification and Functional Analysis of Differentially Expressed Genes in Myzus persicae (Hemiptera: Aphididae) in Response to Trans-anethole

Plant essential oils, with high bioactivity and biodegradability, provide promising alternatives to synthetic pesticides for pest control. Trans-anethole is the major component of essential oil from star anise, Illicium verum Hook. The compound has a strong contact toxicity against the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), which is a major insect pest of many vegetables and crops. However, little information is known about how M. persicae responds to trans-anethole at the molecular level. We conducted a comparative transcriptome analysis of M. persicae in response to a LD50 dose of trans-anethole. A total of 559 differentially expressed genes were detected in the treated individuals, with 318 genes up-regulated, and 241 genes down-regulated. Gene ontology (GO) analysis revealed that these genes were classified into different biological processes and pathways. We also found that genes encoding ATP-binding cassette (ABC) transporters, DnaJ, and cuticle proteins were dramatically up-regulated in response to trans-anethole. To study the function of these genes, we performed RNA interference (RNAi) analysis. Knockdown of an ABC transporter gene (ABCG4) and a DnaJ gene (DnaJC1) resulted in a significantly increased mortality rate in M. persicae following trans-anethole exposure, indicating the involvement of these two genes in the toxicity response to trans-anethole. The findings provide new insights into the mechanisms of M. persicae in coping with plant essential oils.

Comparative transcriptome analysis of thiamethoxam susceptible and resistant Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae), using RNA-sequencing

Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), transmits the causal pathogen of huanglongbing and is a global pest of citrus. D. citri populations exhibit resistance to multiple insecticide modes of action in areas where these chemicals have been overused. We performed genome-wide transcriptional analysis for two field populations of D. citri (Wauchula and Lake Alfred, Florida, USA) that exhibit 1300-fold resistance to the neonicotinoid insecticide, thiamethoxam, and compared it to that of susceptible psyllids collected from the same area and without imposed selection. The Lake Alfred population responded to insecticide resistance by up-regulation of 240 genes and down-regulation of 148 others. The Wauchula population exhibited similar patterns to the Lake Alfred population with up-regulation of 253 genes and down-regulation of 115 others. Gene Ontology annotation associated with cellular processes, cell, and catalytic activity were assigned to differentially expressed genes (DEGs). The DEGs from Lake Alfred and Wauchula populations were mapped to Kyoto Encyclopedia of Gene and Genomes pathways and implicated enrichment of metabolic pathways, oxidative phosphorylation, extracellular matrix-receptor interaction, terpenoid backbone biosynthesis, and insect hormone biosynthesis in the resistant populations. Up-regulation of 60s ribosomal proteins, UDP-gluscoyltransferases, cytochrome c oxidases, and CYP and ABC transporters among thiamethoxam-resistant D. citri implicates a broad array of novel and conventionally understood resistance mechanisms.

Identification and the potential roles of long non-coding RNAs in regulating acetyl-CoA carboxylase ACC transcription in spirotetramat-resistant Aphis gossypii

Long non-coding RNAs (lncRNAs) represent the largest class of non-coding transcripts. They act a pivotal part in various insect developmental processes and stress responses. However, the investigation of lncRNA functions in insecticide resistant remains at an early phase. Herein, we conducted whole-transcriptome RNA sequencing for two cotton aphid (Aphis gossypii Glover) strains, i.e., insecticide-susceptible (SS) and spirotetramat-resistant (SR). We discovered 6059 lncRNAs in the RNA-Seq data, and 874 lncRNAs showed differential expression. In addition, 5 lncRNAs among 874 lncRNAs were predicted as targets of acetyl-CoA carboxylase (ACC). Reverse transcription real-time quantitative PCR (RT-qPCR) combined with RNA interference (RNAi) confirmed that selected ACC lncRNA was related to the expression of ACC. Moreover, we also identified two transcription factors, i.e., C/EBP and C/EBPzeta, that regulate the transcription level of ACC lncRNA. These results provide a good basis for the study of cotton aphid lncRNA functions in insecticide resistance development.

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.

Overexpression of ATP-binding cassette transporters associated with sulfoxaflor resistance in Aphis gossypii glover

BACKGROUND

Sulfoxaflor is a new insecticide for controlling against Aphis gossypii in the field. ATP-binding cassette (ABC) transporters belong to a large superfamily of proteins and play an important role in the detoxification process. However, the potential role of ABC transporters in sulfoxaflor resistance in A. gossypii is unknown.

RESULTS

In this study, an ABC transporter inhibitor, verapamil, dramatically increased the toxicity of sulfoxaflor in the resistant population with a synergistic ratio of 8.55. However, verapamil did not synergize sulfoxaflor toxicity in the susceptible population. The contents of ABC transporters were significantly increased in the Sul-R population. Based on RT-qPCR analysis, 10 of 23 ABC transcripts, ABCA1, ABCA2, ABCB1, ABCB5, ABCD1, ABCG7, ABCG16, ABCG26, ABCG27, and MRP7, were up-regulated in the Sul-R population compared to the Sus population. Meanwhile, inductive effects of ABCA1, ABCD1, ABCG7 and ABCG26 by sulfoxaflor were found in A. gossypii. Furthermore, knockdown of ABCA1 and ABCD1 using RNAi significantly increased the sulfoxaflor sensitivity in Sul-R aphids.

CONCLUSION

These results suggested that ABC transporters, especially the ABCA1 and ABCD1 genes, might be related with sulfoxaflor resistance in A. gossypii. This study will promote further work to validate the functional roles of these ABCs in sulfoxaflor resistance and might be helpful for the management of sulfoxaflor-resistant A. gossypii.

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.