Transcriptome analysis of Spodoptera litura reveals the molecular mechanism to pyrethroids resistance

Beta-cypermethrin-induced stress response and ABC transporter-mediated detoxification in Tetrahymena thermophila

β-Cypermethrin (β-CYP), a synthetic pyrethroid pesticide, is widely used for insect management. However, it also affects non-target organisms and pollutes aquatic ecosystems. Tetrahymena thermophila, a unicellular ciliated protist found in fresh water, is in direct contact with aquatic environments and sensitive to environmental changes. The proliferation of T. thermophila was inhibited and the cellular morphology changed under β-CYP stress. The intracellular ROS level significantly increased, and SOD activity gradually rose with increasing β-CYP concentrations. Under 25 mg/L β-CYP stress, 687 genes were up-regulated, primarily enriched in the organic cyclic compound binding and heterocyclic compound binding pathways. These include 8 ATP-binding cassette transporters (ABC) family genes, 2 cytochrome P450 monooxygenase genes, and 2 glutathione peroxidase related genes. Among of them, ABCG14 knockdown affected cellular proliferation under β-CYP stress. In contrast, overexpression of ABCG14 enhanced cellular tolerance to β-CYP. The results demonstrated that Tetrahymena tolerates high β-CYP concentration stress through various detoxification mechanisms, with ABCG14 playing a crucial role in detoxification of β-CYP.

Effects of surfactin stress on gene expression and pathological changes in Spodoptera litura

Spodoptera litura (S. litura) is a polyphagous pest of the family Lepidoptera, which causes damage and yields losses to many crops. The long-term use of chemical pesticides for control not only seriously threatens environmental health, but also causes S. litura to develop drug resistance. Therefore, there is an urgent need to develop environmentally safe and friendly biogenic pesticides. However, the mechanism of action of the secondary metabolite (surfactin) of Bacillus Vélezensis (B. vélezensis) on lepidopteran pests (S. litura) has not been reported yet. We found that several metabolites and genes in S. litura were affected by surfactin exposure. The expressions of the metabolites (protoporphyrinogen (PPO), gluconolactone (GDL), and L-cysteate) were significantly down-regulated while glutamate and hydroxychloroquine were significantly up-regulated. The expression levels of genes related to drug metabolism and detoxification, include the glutathione s-transferase (GST) gene family and acetaldehyde dehydrogenase (ALDH), and apoptosis-inhibiting genes (seven in absentia homolog 1(SIAH1)) were significantly decreased. In addition, pathological changes occurred in intestinal wall cells, Malpighian tubule cells, and nerve cells of S. litura under surfactin stress. Conclusively, our results suggest that surfactin induces an increase in reactive oxygen species (ROS) and damages S. litura cells. Furthermore, based on the integrated analysis of transcriptomic and metabolomic data, it is hypothesized that surfactin may also trigger neurotoxicity and cardiotoxicity in S. litura while hindering the insect's detoxification processes. This study lays a foundation for further exploration of surfactin as a potential biopesticide.

The effect of lambda-cyhalothrin nanocapsules on the gut microbial communities and immune response of the bee elucidates the potential environmental impact of emerging nanopesticides

Emerging nanopesticides are gradually gaining widespread application in agriculture due to their excellent properties, but their potential risks to pollinating insects are not fully understood. In this study, lambda-cyhalothrin nanocapsules (LC-NCs) were constructed by electrostatic self-assembly method with iron mineralization optimization, and their effects on bee gut microbial communities and host immune-related factors were investigated. Microbiome sequencing revealed that LC-NCs increase the diversity of gut microbial communities and reduce the complexity of network features, disrupting the overall structure of the microbial communities. In addition, LC-NCs also had systemic effects on the immune response of bees, including increased activity of SOD and CAT enzymes and expression of their genes, as well as downregulation of Defensin1. Furthermore, we noticed that the immune system of the host was activated simultaneously with a rise in the abundance of beneficial bacteria in the gut. Our research emphasizes the importance of both the host and gut microbiota of holobiont in revealing the potential risks of LC-NCs to environmental indicators of honey bees, and provides references for exploring the interactions between host-microbiota systems under exogenous stress. At the same time, we hope that more research can focus on the potential impacts of nanopesticides on the ecological environment.

Impact of Sublethal Insecticides Exposure on Vespa magnifica: Insights from Physiological and Transcriptomic Analyses

Insecticides are widely used to boost crop yields, but their effects on non-target insects like Vespa magnifica are still poorly understood. Despite its ecological and economic significance, Vespa magnifica has been largely neglected in risk assessments. This study employed physiological, biochemical, and transcriptomic analyses to investigate the impact of sublethal concentrations of thiamethoxam, avermectin, chlorfenapyr, and β-cypermethrin on Vespa magnifica. Although larval survival rates remained unchanged, both pupation and fledge rates were significantly reduced. Enzymatic assays indicated an upregulation of superoxide dismutase and catalase activity alongside a suppression of peroxidase under insecticide stress. Transcriptomic analysis revealed increased adenosine triphosphate-related processes and mitochondrial electron transport activity, suggesting elevated energy expenditure to counter insecticide exposure, potentially impairing essential functions like flight, hunting, and immune response. The enrichment of pathways such as glycolysis, hypoxia-inducible factor signaling, and cholinergic synaptic metabolism under insecticide stress highlights the complexity of the molecular response with notable effects on learning, memory, and detoxification processes. These findings underscore the broader ecological risks of insecticide exposure to non-target insects and highlight the need for further research into the long-term effects of newer insecticides along with the development of strategies to safeguard beneficial insect populations.

Arecoline inhibits the growth of Spodoptera litura by inducing intestinal metabolic dysfunction

Arecoline (ACL), an active constituent derived from Areca catechu L., exerts various pharmacological effects and serves as a potential plant-based insecticide. However, the effects of ACL on Spodoptera litura, an important and widely distributed agricultural pest, remain unknown. This study aimed to elucidate the mechanism underlying ACL-induced toxicity and its inhibitory effects on larval growth and development through intestinal pathology observations, intestinal transcriptome sequencing, intestinal digestive enzyme activity analysis. The results indicated that ACL exposure leads to pathological alterations in the S. litura midgut. Furthermore, the detection of digestive enzyme activity revealed that ACL inhibits the activities of acetyl CoA carboxylase, lipase, α-amylase, and trypsin. Simultaneously, upregulation of superoxide dismutase activity and downregulation of malondialdehyde levels were observed after ACL exposure. Transcriptome analysis identified 1118 genes that were significantly differentially expressed in the midgut after ACL exposure, potentially related to ACL toxic effects. Notably, ACL treatment downregulated key enzymes involved in lipid metabolism, such as fatty acid binding protein 2-like, pancreatic triacylglycerol lipase-like, pancreatic lipid-related protein 2-like, and fatty acid binding protein 1-like. Taken together, these results suggest that ACL induces midgut damage and impedes larval growth by suppressing digestive enzyme activity in the intestine. These findings can aid in the development of environmentally friendly plant-derived insecticides, utilizing ACL to effectively combat S. litura proliferation.

Uridine diphosphate (UDP)-glycosyltransferases (UGTs) are associated with insecticide resistance in the major malaria vectors Anopheles gambiae s.l. and Anopheles funestus

Malaria remains one of the highest causes of morbidity and mortality, with 249 million cases and over 608,000 deaths in 2022. Insecticides, which target the Anopheles mosquito vector, are the primary method to control malaria. The widespread nature of resistance to the most important insecticide class, the pyrethroids, threatens the control of this disease. To reverse the stall in malaria control there is urgent need for new vector control tools, which necessitates understanding the molecular basis of pyrethroid resistance. In this study we utilised multi-omics data to identify uridine-diphosphate (UDP)-glycosyltransferases (UGTs) potentially involved in resistance across multiple Anopheles species. Phylogenetic analysis identifies sequence similarities between Anopheline UGTs and those involved in agricultural pesticide resistance to pyrethroids, pyrroles and spinosyns. Expression of five UGTs was characterised in An. gambiae and An. coluzzii to determine constitutive over-expression, induction, and tissue specificity. Furthermore, a UGT inhibitor, sulfinpyrazone, restored susceptibility to pyrethroids and DDT in An. gambiae, An. coluzzii, An. arabiensis and An. funestus, the major African malaria vectors. Taken together, this study provides clear association of UGTs with pyrethroid resistance as well as highlighting the potential use of sulfinpyrazone as a novel synergist for vector control.

Effects of Bacillus thuringiensis Treatment on Expression of Detoxification Genes in Chlorantraniliprole-Resistant Plutella xylostella

Detoxification genes are crucial to insect resistance against chemical pesticides, yet their expression may be altered by exposure to biopesticides such as spores and insecticidal proteins of Bacillus thuringiensis (Bt). Increased enzymatic levels of selected detoxification genes, including glutathione S-transferase (GST), cytochrome P450 (CYP450), and carboxylesterase (CarE), were detected in chlorantraniliprole (CAP)-resistant strains of the diamondback moth (DBM, Plutella xylostella) from China when compared to a reference susceptible strain. These CAP-resistant DBM strains displayed distinct expression patterns of GST 1, CYP6B7, and CarE-6 after treatment with CAP and a Bt pesticide (Bt-G033). In particular, the gene expression analysis demonstrated significant upregulation of the CYP6B7 gene in response to the CAP treatment, while the same gene was downregulated following the Bt-G033 treatment. Downregulation of CYP6B7 using RNAi resulted in increased susceptibility to CAP in resistant DBM strains, suggesting a role of this gene in the resistant phenotype. However, pretreatment with a sublethal dose of Bt-G033 inducing the downregulation of CYP6B7 did not significantly increase CAP potency against the resistant DBM strains. These results identify the DBM genes involved in the metabolic resistance to CAP and demonstrate how their expression is affected by exposure to Bt-G033.

SlCarE054 in Spodoptera litura (Lepidoptera: Noctuidae) showed direct metabolic activity to β-cypermethrin with stereoselectivity

Carboxylesterases (CarEs) is an important detoxification enzyme system in phase Ⅰ participating in insecticides resistance. In our previous study, SlCarE054, a CarEs gene from lepidoptera class, was screened out to be upregulated in a pyrethroids and organophosphates resistant population. Its overexpression was verified in two field-collected populations of Spodoptera litura (Lepidoptera: Noctuidae) resistant to pyrethroids and organophosphates by qRT-PCR. Spatiotemporal expression results showed that SlCarE054 was highly expressed in the pupae stage and the digestive tissue midgut. To further explore its role in pyrethroids and organophosphates resistance, its metabolism activity to insecticides was determined by UPLC. Its recombinant protein showed significant metabolism activity to cyhalothrin and fenvalerate, but not to phoxim or chlorpyrifos. The metabolic activity of SlCarE054 to β-cypermethrin showed stereoselectivity, with higher metabolic activity to θ-cypermethrin than the enantiomer α-cypermethrin. The metabolite of β-cypermethrin was identified as 3-phenoxybenzaldehyde. Further modelling and docking analysis indicated that β-cypermethrin, cyhalothrin and fenvalerate could bind with the catalytic triad of the 3D structure of SlCarE054. The interaction of β-cypermethrin with SlCarE054 also showed the lowest binding energy. Our work provides evidence that SlCarE054 play roles in β-cypermethrin resistance in S. litura.

P450 gene CYP6a13 is responsible for cross-resistance of insecticides in field populations of Spodoptera frugiperda

Continuous and long-term use of traditional and new pesticides can result in cross-resistance among pest populations in different fields. Study on the mechanism of cross-resistance and related genes will help resistance management and field pest control. In this study, the pesticide-resistance mechanism in Spodoptera frugiperda (FAW) was studied with field populations in 3 locations of South China. Field FAW populations were highly resistant to traditional insecticides, chlorpyrifos (organophosphate) and deltamethrin (pyrethroid), and had higher levels of cytochrome P450 activity than a non-resistant laboratory strain. Inhibition of P450 activity by piperonyl butoxide significantly increased the sensitivity of resistant FAW in 3 locations to chlorpyrifos, deltamethrin and chlorantraniliprole (amide), a new type of insecticide, suggesting that P450 detoxification is a critical factor for insecticide resistance in field FAW populations. Transcriptomic analysis indicated that 18 P450 genes were upregulated in the field FAW populations collected in 3 regions and in 2 consecutive years, with CYP6a13, the most significantly upregulated one. Knockdown of CYP6a13 messenger RNA by RNA interference resulted in an increased sensitivity to the 3 tested insecticides in the field FAW. Enzyme activity and molecular docking analyses indicated that CYP6a13 enzyme was able to metabolize the 3 tested insecticides and interact with 8 other types of insecticides, confirming that CYP6a13 is a key cross-resistance gene with a wide range of substrates in the field FAW populations across the different regions and can be used as a biomarker and target for management of FAW insecticide resistance in fields.

Determination of internal controls for quantitative gene expression of Spodoptera litura under microbial pesticide stress

Quantitative real-time polymerase chain reaction (qRT-PCR) has become a commonly used method for the quantification of gene expression. However, accurate qRT-PCR analysis requires a valid internal reference for data normalization. To determine the valid reference characterized with low expression variability among Spodoptera litura samples after microbial pesticide treatments, nine housekeeping genes, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), arginine kinase, ubiquitin C, actin-5C (ACT5C), actin, ribosomal protein S13 (RPS13), tubulin, acidic ribosomal protein P0 (RPLP0) and ubiquinol-cytochrome c reductase, were evaluated for their suitability using geNorm, Normfinder, BestKeeper, RefFinder and the comparative delta CT methods in this study. S. litura larvae after direct treatment (larvae were immersed in biopesticides), indirect treatment (larvae were fed with biopesticide immersed artificial diets) and comprehensive treatment (larvae were treated with the first two treatments in sequence), respectively with Metarhizium anisopliae, Empedobacter brevis and Bacillus thuringiensis, were investigated. The results indicated that the best sets of internal references were as follows: RPLP0 and ACT5C for direct treatment conditions; RPLP0 and RPS13 for indirect treatment conditions; RPS13 and GAPDH for comprehensive treatment conditions; RPS13 and RPLP0 for all the samples. These results provide valuable bases for further genetic researches in S. litura.

Comprehensive analysis of the overexpressed cytochrome P450-based insecticide resistance mechanism in Spodoptera litura

Cytochrome P450s play critical roles in the metabolic resistance of insecticides in insects. Previous findings showed that enhanced P450 activity was an important mechanism mediating indoxacarb resistance, and multiple P450 genes were upregulated in indoxacarb resistant strains of Spodoptera litura. However, the functions of these P450 genes in insecticide resistance remain unknown. Here, the P450 inhibitor PBO effectively decreased the resistance of S. litura to indoxacarb. Ten upregulated P450 genes were characterized, all of which were overexpressed in response to indoxacarb induction. Knockdown of nine P450 genes decreased cell viability against indoxacarb, and further silencing of three genes (CYP339A1, CYP340G2, CYP321A19) in larvae enhanced the sensitivity to indoxacarb. Transgenic overexpression of these three genes increased resistance to indoxacarb in Drosophila melanogaster. Moreover, molecular modeling and docking predicted that these three P450 proteins could bind tightly to indoxacarb and N-decarbomethoxylated metabolite (DCJW). Interestingly, these three P450 genes may also mediate cross-resistance to chlorantraniliprole, λ-cyhalothrin and imidacloprid. Additionally, heterologous expression and metabolic assays confirmed that three recombinant P450s could effectively metabolize indoxacarb and DCJW. This study strongly demonstrates that multiple overexpressed mitochondrial and microsomal P450 genes were involved in insecticide resistance in S. litura.

Identification of inducible CYP3 and CYP4 genes associated with abamectin tolerance in the fat body and Malpighian tubules of Spodoptera litura

Abamectin, as a broad-spectrum bioinsecticide, has been widely used for the control of Lepidoptera insects, resulting in different levels of resistance to abamectin in Spodoptera litura. Cytochrome P450 monooxygenases (P450s) are known for their important roles in insecticide detoxification. In this study, the expression of SlCYP6B40, SlCYP4L12 and SlCYP9A32 in the fat body, and SlCYP4S9, SlCYP6AB12, SlCYP6AB58, SlCYP9A75a and SlCYP9A75b in Malpighian tubules was found to be significantly upregulated after abamectin exposure. SlCYP6AE44 and SlCYP6AN4 were simultaneously upregulated in these two tissues after abamectin exposure. Ectopically overexpressed SlCYP6AE44, SlCYP9A32 and SlCYP4S9 in transgenic Drosophila conferred tolerance to abamectin. In addition, homology modeling and molecular docking results suggested that SlCYP6AE44, SlCYP9A32 and SlCYP4S9 may be capable of binding with abamectin. These results demonstrate that upregulation of CYP3 and CYP4 genes may contribute to abamectin detoxification in S. litura and provide information for evidence-based insecticide resistance management strategies.

Transcriptome analysis unveils the mechanisms of lipid metabolism response to grayanotoxin I stress in Spodoptera litura

Background

Spodoptera litura (tobacco caterpillar, S. litura) is a pest of great economic importance due to being a polyphagous and world-distributed agricultural pest. However, agricultural practices involving chemical pesticides have caused resistance, resurgence, and residue problems, highlighting the need for new, environmentally friendly methods to control the spread of S. litura.

Aim

This study aimed to investigate the gut poisoning of grayanotoxin I, an active compound found in Pieris japonica, on S. litura, and to explore the underlying mechanisms of these effects.

Methods

S. litura was cultivated in a laboratory setting, and their survival rate, growth and development, and pupation time were recorded after grayanotoxin I treatment. RNA-Seq was utilized to screen for differentially expressed genes (DEGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted to determine the functions of these DEGs. ELISA was employed to analyze the levels of lipase, 3-hydroxyacyl-CoA dehydrogenase (HOAD), and acetyl-CoA carboxylase (ACC). Hematoxylin and Eosin (H & E) staining was used to detect the development of the fat body.

Results

Grayanotoxin I treatment significantly suppressed the survival rate, growth and development, and pupation of S. litura. RNA-Seq analysis revealed 285 DEGs after grayanotoxin I exposure, with over 16 genes related to lipid metabolism. These 285 DEGs were enriched in the categories of cuticle development, larvae longevity, fat digestion and absorption. Grayanotoxin I treatment also inhibited the levels of FFA, lipase, and HOAD in the hemolymph of S. litura.

Conclusion

The results of this study demonstrated that grayanotoxin I inhibited the growth and development of S. litura. The mechanisms might, at least partly, be related to the interference of lipid synthesis, lipolysis, and fat body development. These findings provide valuable insights into a new, environmentally-friendly plant-derived insecticide, grayanotoxin I, to control the spread of S. litura.

DIMBOA-induced gene expression, activity profiles of detoxification enzymes, multi-resistance mechanisms, and increased resistance to indoxacarb in tobacco cutworm, Spodoptera litura (Fabricius)

Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) is one of the most destructive insect pests owned strong resistance to different insecticides. Indoxacarb as a novel oxadiazine insecticide becomes the main pesticide against S. litura. DIMBOA [2,4-dihydroxy-7-methoxy-2 H-1,4-benz-oxazin-3(4 H)-one] is involved in important chemical defense processes in corn plants. However, the insects' adaptation mechanism to insecticides when exposed to defensive allelochemicals in their host plants remains unclear. Here, we assessed multi-resistance, and resistance mechanisms based on S. litura life history traits. After 18 generations of selection, indoxacarb resistance was increased by 61.95-fold (Ind-Sel) and 86.06-fold (Dim-Sel) as compared to the Lab-Sus. Also, DIMBOA-pretreated larvae developed high resistance to beta-cypermethrin, chlorpyrifos, phoxim, chlorantraniliprole, and emamectin benzoate. Meanwhile, indoxacarb (LC50) was applied to detect its impact on thirty-eight detoxification-related genes expression. The transcripts of SlituCOE073, SlituCOE009, SlituCOE074, and SlituCOE111 as well as SlGSTs5, SlGSTu1, and SlGSTe13 were considerably raised in the Ind-Sel strain. Among the twenty-three P450s, CYP6AE68, CYP321B1, CYP6B50, CYP9A39, CYP4L10, and CYP4S9v1 transcripts denoted significantly higher levels in the Ind-Sel strain, suggesting that CarEs, GSTs and P450s genes may be engaged in indoxacarb resistance. These outcomes further highlighted the importance of detoxification enzymes for S. litura gene expression and their role in responses to insecticides and pest management approaches.

Inducible Cytochrome P450s in the Fat Body and Malpighian Tubules of the Polyphagous Pests of Spodoptera litura Confer Xenobiotic Tolerance

Cytochrome P450 plays vital roles in detoxifying xenobiotics. In this study, SlCYP340A and SlCYP340L expression in the Spodoptera litura fat body and SlCYP332A1, SlCYP6AB12, SlCYP6AB58, SlCYP6AB59, and SlCYP6AN4 expression in the Malpighian tubules were significantly upregulated after cyantraniliprole exposure, and SlCYP6AB58 and SlCYP6AB59 expression levels were simultaneously increased in the Malpighian tubules after gossypol treatment. Drosophila ectopically expressing candidate P450 genes showed that SlCYP332A1, SlCYP6AB12, SlCYP6AB59, SlCYP6AN4, and SlCYP340A conferred cyantraniliprole tolerance. The overexpression of SlCYP6AB58 and SlCYP6AB59 in Drosophila increased the number of eggs laid under the gossypol treatment. Moreover, the knockdown of SlCYP332A1, SlCYP6AB12, SlCYP6AB59, SlCYP6AN4, and SlCYP340A increased S. litura mortality under the cyantraniliprole treatment. Homology modeling and molecular docking results suggested that candidate P450 has the potential to bind with cyantraniliprole. These results indicate that the CYP3 and CYP4 genes participate in cyantraniliprole detoxification and that SlCYP6AB59 may be simultaneously involved in the gossypol tolerance of S. litura.

Identification and functional study of detoxification-related genes in response to tolfenpyrad stress in Glyphodes pyloalis Walker (Lepidoptera: Pyralidae)

Glyphodes pyloalis Walker (G. pyloalis) is a common destructive mulberry pest. Due to the long-term and frequent use of insecticides, it has developed tolerance to commonly used insecticides. Tolfenpyrad (TFP) is a novel pyrazole heterocyclic insecticide. In order to understand the TFP detoxification mechanism of G. pyloalis larvae, we first estimated the LC30 dose of TFP for 3rd instar G. pyloalis larvae. Next, we identified genes that were differentially expressed in 3rd instar G. pyloalis larvae treated with TFP compared to the control group by transcriptome sequencing. In total, 86,949,569 and 67,442,028 clean reads were obtained from TFP-treated and control G. pyloalis larvae, respectively. A total of 5588 differentially expressed genes (DEGs) were identified in TFP-treated and control G. pyloalis larvae, of which 3084 genes were upregulated and 2504 genes were downregulated. We analyzed the expression of 43 candidate detoxification enzyme genes associated with insecticide tolerance using qPCR. According to the spatiotemporal expression pattern of DEGs, we found that CYP6ABE1, CYP333A36 and GST-epsilon8 were highly expressed in the midgut, while CarEs14 was strongly expressed in haemolymph. Furthermore, we successfully knocked down these genes by RNA interference. After silencing CYP6ABE1 and CYP333A36, bioassay showed that the mortality rate of TFP-treated G. pyloalis larvae was significantly higher compared to the control group. This study provides a theoretical foundation for understanding the sensitivity of G. pyloalis to TFP and establish the basis for the effective and green management of this pest.

RNA interference in cytochrome P450 monooxygenase (CYP) gene results in reduced insecticide resistance in Megalurothrips usitatus Bagnall

Genes of the cytochrome P450 (CYP450) superfamily are known to be involved in the evolution of insecticide resistance. In this study, the transcriptomes of two Megalurothrips usitatus Bagnall (Thysanoptera: Thripidae) strains (resistant and susceptible) were screened for detoxification genes. MusiDN2722 encodes a protein composed of 504 amino acid residues with a relative molecular mass of 57.3 kDa. Multiple sequence alignment and phylogenetic analysis showed that MusiDN2722 is a member of the CYP450 family and has characteristics of the conserved CYP6 domain shared by typical CYP450 family members. RT-qPCR (real-time quantitative polymerase chain reaction) analysis showed that MusiDN2722 was upregulated in the acetamiprid-resistant strain compared with the susceptible strain (p < 0.05), and the relative expression level was significantly higher at 48 h after exposure than at 24 h after exposure. The interference efficiency of the injection method was higher than that of the membrane-feeding method. Silencing of MusiDN2722 through RNA interference significantly increased the sensitivity of M. usitatus to acetamiprid. Overall, this study revealed that MusiDN2722 plays a crucial role in the resistance of M. usitatus to acetamiprid. The findings will not only advance our understanding of the role of P450s in insecticide resistance but also provide a potential target for the sustainable control of destructive pests such as thrips.

Effects of azadirachtin on detoxification-related gene expression in the fat bodies of the fall armyworm, Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda, has become a worldwide pest and threatens world food production. A previous study indicated that azadirachtin, the most effective botanical insecticide for S. frugiperda, inhibits larval growth of the insect. The effect of azadirachtin on the tissues of the larvae, however, remains to be determined. In this study, the effects of azadirachtin on the structure of fat bodies were analyzed. Comparative transcriptomic analysis was conducted between controls and samples treated with 0.1 μg/g azadirachtin for 7 days to explore potential relevant mechanisms. The expression of 5356 genes was significantly affected after azadirachtin treatment, with 3020 up-regulated and 2336 down-regulated. Among them, 137 encode detoxification enzymes, including 53 P450s, 20 GSTs, 27 CarEs, 16 UGTs, and 12 ABC transporters. Our results indicated that azadirachtin could destroy fat body structure and change the mRNA levels of detoxification-related genes. The up-regulated genes encoding detoxification enzymes might be related to detoxifying azadirachtin. Our results elucidate a preliminary mechanism of azadirachtin detoxification in the fat bodies of S. frugiperda larvae.

Decreased cuticular penetration minimizes the impact of the pyrethroid insecticide λ-cyhalothrin on the insect predator Eocanthecona furcellata

The use of broad-spectrum pesticides may reduce the biological control efficacy of predatory arthropods. Hence, the risks of pesticides to predators need to be evaluated. Here, we assessed the effects of a broad spectrum pyrethroid λ-cyhalothrin on a polyphagous predatory insect Eocanthecona furcellata via contact exposure route. The recommended application rate of λ-cyhalothrin was lower than the LR₅₀ and HQ _(in-field) was equal to 0.57, indicating the risk of λ-cyhalothrin to E. furcellata was low. Dried λ-cyhalothrin residue had no effect on the mortality, body weight, protein content of cuticle, or activities of major detoxification enzymes in E. furcellata. Residual of λ-cyhalothrin was only detected in the cuticle and legs of E. furcellata with a decreasing trend as time went by and no λ-cyhalothrin was detected inside the body. Additionally, a comparative transcriptome analysis was conducted to study global changes in gene expression in E. furcellata at different time points following exposure to λ-cyhalothrin-contaminated environment. A total of 57,839 unigenes with an average length of 1044 bp and an N50 of 1820 bp were obtained. In total, 118 and 109 differentially expressed genes (DEGs) at 12 h, and 60 h were identified between two groups. The DEGs were largely enriched in functional categories related to the structural constituent of cuticle. Accordingly, multiple cuticle protein-coding genes were up-regulated at 12 h after pesticide exposure. The present study stressed the importance of evaluating the compatibility between a specific pesticide (λ-cyhalothrin) and E. furcellata via simulating the releasing predators after insecticide application. The data could help optimize the pesticide use, optimizing the ecological services of E. furcellata as a BCA, and expanding its use into more areas of agriculture.

Characterization and expression profiling of G protein-coupled receptors (GPCRs) in Spodoptera litura (Lepidoptera: Noctuidae)

Spodoptera litura is a highly destructive omnivorous pest, and they caused serious damage to various crops. G protein-coupled receptors (GPCRs) mediate dozens of physiological processes including reproduction, development, life span and behaviors, but the information of these receptors has been lacking in S. litura. Here, we methodically identified 122 GPCRs in S. litura and made an assay of their expression patterns in different tissues. Comparing the identified GPCRs with homologous genes of other insects, it is obvious that the subfamily A2 (biogenic amine receptors) and the subfamily A3 (neuropeptide and protein hormone receptors) of S. litura have expanded to a certain extent, which may be related to the omnivorous nature and drought environment resistance of S. litura. Besides, the large Methuselah (Mth)/Methuselah-like (Mthl) subfamily of S. litura may be involved in many physiological functions such as longevity and stress response. Apart from duplicate receptors, the loss of parathyroid hormone receptor (PTHR) and the bride of sevenless (Boss) receptor in the lepidopteran insects may imply a new pattern of wing formation and energy metabolism in lepidopteran insects. In addition, the high expression level of GPCRs in different tissues reflects the functional diversity of GPCRs regulating. Systemic identification and initial characterization of GPCRs in S. litura provide a basis for further studies to reveal the functions of these receptors in regulating physiology and behavior.

Gut transcriptome analysis of P450 genes and cytochrome P450 reductase in three moth species feeding on gymnosperms or angiosperms

Cytochrome P450 enzymes (P450s, CYPs) are a superfamily of heme–thiolate proteins involved in the metabolism of endogenous and exogenous substances in insects. In this study, the identification of putative P450 proteins was done and the elimination of the repeated sequences resulted in 57 proteins from Gastropacha populifolia, 63 proteins from Dendrolimus punctatus, and 53 proteins from Dendrolimus tabulaeformis. The putative P450 proteins were aligned together with seven other insect species based on five conserved domains. A total of ten co-orthologous groups were identified. Interestingly, one co-orthologous gene, CYP4g15 in CYP4 clan, was identified and its 3D structure analysis showed that the highly conserved sites of the predicted motifs were close to the active sites of P450. Furthermore, this study revealed that insect CYP4g15 and two bacteria cytochrome P450 were monophyletic. This suggests that insects CYP4g15 are not only functionally conserved but also an ancient gene originating from different bacteria species.

CRISPR/Cas9-Mediated Knockout Reveals the Involvement of CYP304F1 in β-Cypermethrin and Chlorpyrifos Resistance in Spodoptera litura

Functions of insect CYP2 clan P450s in insecticide resistance are relatively less reported. In Spodoptera litura, a gene from the CYP2 clan (CYP304F1) was validated to be up-regulated significantly in a pyrethroid- and organophosphate-resistant population (QJ) than a susceptible population by RNA-Seq and qRT-PCR. Spatial-temporal expression indicated the high expression of CYP304F1 in the fourth, fifth, and sixth instar larvae and the metabolism-related tissue fat body and malpighian tubules. CYP304F1 was knocked out by CRISPR/Cas9, and a homozygous population (QJ-CYP304F1) with a G-base deletion at exon 2 was obtained after selection. Bioassay results showed that the LD₅₀ values to β-cypermethrin and chlorpyrifos in the QJ-CYP304F1 population decreased significantly, and the resistance ratio was both 1.81-fold in the QJ population compared with that in the QJ-CYP304F1 population. The toxicity of fenvalerate, cyhalothrin, or phoxim showed no significant change. These results suggested that CYP304F1 is involved in β-cypermethrin and chlorpyrifos resistance in S. litura.

Acylsugar protection of Nicotiana benthamiana confers mortality and transgenerational fitness costs in Spodoptera litura

Acylsugars are secondary metabolites that are produced in the trichomes of some solanaceous species and can help control several herbivorous insect pests. Previously, knockout mutations (asat2 mutants) were shown to significantly reduce the acylsugar content of Nicotiana benthamiana, and significantly improve the fitness of six generalist insect herbivores. The current study compared the significant mortality and fitness costs in Spodoptera litura conferred by acylsugar protection of N. benthamiana (wild-type plants) compared to S. litura strains reared in acylsugar-deficient plants with depleted acylsugar biosynthesis. Acylsugar protection prolonged the developmental duration and decreased viability in the larval stages. Further, the fecundity of females and the hatching rate of eggs significantly decreased under acylsugar protection. For F₁ offspring, acylsugar protection still exerted significant negative effects on larval survival rate and fecundity per female. The net reproductive rate and relative fitness of the S. litura strain were strongly affected by acylsugar. Altogether, these results indicate that acylsugar could contribute to plant protection due to toxicity to pests, diffused availability, and low environmental persistence. This could represent a complementary and alternative strategy to control populations of insect pests.

Metabolism and antioxidant activity of SlGSTD1 in Spodoptera litura as a detoxification enzyme to pyrethroids

Glutathione S-transferase (GSTs) are members of multifunction enzymes in organisms and mostly known for their roles in insecticide resistance by conjugation. Spodoptera litura (Fabricius) is a voracious agricultural pest widely distributed in the world with high resistance to various insecticides. The function of GSTs in the delta group of S. litura is still lacking. Significantly up-regulation of SlGSTd1 was reported in four pyrethroids-resistant populations and a chlorpyrifos-selected population. To further explore its role in pyrethroids and organophosphates resistance, the metabolism and peroxidase activity of SlGSTD1 were studied by heterologous expression, RNAi, and disk diffusion assay. The results showed that K_m and V_max for 1-chloro-2,4-dinitrobenzene (CDNB) conjugating activity of SlGSTD1were 1.68 ± 0.11 mmol L⁻¹ and 76.0 ± 2.7 nmol mg⁻¹ min⁻¹, respectively. Cyhalothrin, beta-cypermethrin, and chlorpyrifos had an obvious inhibitory effect on SlGSTD1 activity, especially for fenvalerate, when using CDNB as substrate. Fenvalerate and cyhalothrin can be metabolized by SlGSTD1 in E. coli and in vitro. Also, silencing of SlGSTd1 significantly increased the toxicity of fenvalerate and cyhalothrin, but had no significant effect on the mortality of larvae treated by beta-cypermethrin or chlorpyrifos. SlGSTD1 possesses peroxidase activity using cumene hydroperoxide as a stress inducer. The comprehensive results indicate that SlGSTD1 is involved in fenvalerate and cyhalothrin resistance of S. litura by detoxication and antioxidant capacity.

Characterization of Insecticide Response-Associated Transcripts in the Colorado Potato Beetle: Relevance of Selected Cytochrome P450s and Clothianidin

Simple Summary

The Colorado potato beetle is an insect pest that can significantly harm potato crops. Various approaches are available to mitigate its damages including the use of insecticides. Unfortunately, its ability to develop resistance towards these compounds is substantial, and understanding the basis of this process is of utmost importance to design strategies to limit the impact of this insect. This work thus aims at quantifying the expression of key transcripts coding for proteins associated with insecticide resistance in Colorado potato beetles exposed to four insecticides. Significant variations were observed, notably in insects exposed to the insecticide clothianidin. Interestingly, subsequent reduction of endogenous levels of selected targets modulated by clothianidin was associated with increased insect susceptibility to this neonicotinoid. These results further highlight molecular players with potential relevance for insecticide resistance, and introduce novel targets that underlie clothianidin resistance in the Colorado potato beetle.

Abstract

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) is known for its capacity to cause significant damages to potato crops worldwide. Multiple approaches have been considered to limit its spread including the use of a diverse arsenal of insecticides. Unfortunately, this insect frequently develops resistance towards these compounds. Investigating the molecular bases underlying the response of L. decemlineata against insecticides is of strong interest to ultimately devise novel and targeted approaches aimed at this pest. This work aimed to characterize, via qRT-PCR, the expression status of targets with relevance to insecticide response, including ones coding for cytochrome P450s, glutathione s-transferases, and cuticular proteins, in L. decemlineata exposed to four insecticides; chlorantraniliprole, clothianidin, imidacloprid, and spinosad. Modulation of levels associated with transcripts coding for selected cytochrome P450s was reported in insects treated with three of the four insecticides studied. Clothianidin treatment yielded the most variations in transcript levels, leading to significant changes in transcripts coding for CYP4c1, CYP4g15, CYP6a13, CYP9e2, GST, and GST-1-Like. Injection of dsRNA targeting CYP4c1 and CYP9e2 was associated with a substantial decrease in expression levels and was, in the case of the latter target, linked to a greater susceptibility of L. decemlineata towards this neonicotinoid, supporting a potential role for this target in clothianidin response. Overall, this data further highlights the differential expression of transcripts with potential relevance in insecticide response, as well as generating specific targets that warrant investigation as novel dsRNA-based approaches are developed against this insect pest.

Transcriptomics and metagenomics of common cutworm (Spodoptera litura) and fall armyworm (Spodoptera frugiperda) demonstrate differences in detoxification and development

BACKGROUND

Spodoptera litura is an important polyphagous pest that causes significant damage to the agricultural sector. We performed RNA-seq of 15 S. litura individuals from larval (fifth and sixth instar larvae), chrysalis, and adult developmental stages. We also compared the S. litura transcriptome data with Spodoptera frugiperda across the same developmental stages, which was sequenced in our previous study.

RESULTS

A total of 101,885 differentially expressed transcripts (DETs) were identified in S. litura. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that S. litura may undergo active xenobiotic and detoxifying metabolism during its larval and adult stages, which may explain difficulties with current population control measures. We also found that DETs of single-copy orthologous genes between S. litura and S. frugiperda were involved in basic metabolism and development. However, energy and metabolic processes genes had a higher expression in S. litura, whereas nervous and olfactory function genes had a higher expression in S. frugiperda. Metagenomics analysis in larval S. litura and S. frugiperda revealed that microbiota participate in the detoxification and metabolism processes, but the relative abundance of detoxification-related microbiota was more abundant in S. frugiperda. Transcriptome results also confirmed the detoxification-related pathway of S. frugiperda was more abundant than in S. litura.

CONCLUSIONS

Significant changes at transcriptional level were identified during the different development stages of S. litura. Importantly, we also identified detoxification associated genes and gut microbiota between S. litura and S. frugiperda at different developmental stages, which will be valuable in revealing possible mechanisms of detoxification and development in these two lepidopterans.

Transcriptome and Metabonomics Analysis Revealed the Molecular Mechanism of Differential Metabolite Production of Dendrobium nobile Under Different Epiphytic Patterns

The cultivation medium of Dendrobium nobile has an effect on the contents of its main medicinal components, but the specific mechanism is still unclear. In this study, the callus, seedlings, rhizomes, and leaves of D. nobile were sequenced for the PacBio SMRT. The 2-year-old stems were selected for the Illumina sequencing and metabolome sequencing to analyze the genetic mechanism of metabolic differences under different epiphytic patterns. As a result, a total of 387 differential genes were obtained, corresponding to 66 differential metabolites. Different epiphytic patterns can induce a series of metabolic changes at the metabolome and transcriptome levels of D. nobile, including flavonoid metabolism, purine metabolism, terpenoid backbone biosynthesis, amino acid metabolism, and alpha-linolenic acid metabolic, and related regulatory genes include ALDH2B7, ADC, EPSPS-1, SHKA, DHAPS-1, GES, ACS1, SAHH, ACS2, CHLP, LOX2, LOX2.3, and CYP74B2. The results showed that the genetic mechanism of D. nobile under various epiphytic patterns was different. In theory, the content of metabolites under the epiphytic patterns of Danxia stone is higher, which is more suitable for field cultivation.

Contribution of multiple overexpressed carboxylesterase genes to indoxacarb resistance in Spodoptera litura

BACKGROUND

As an important family of detoxification enzymes, carboxylesterases (CarEs) have important roles in the development of insecticide resistance in almost all agricultural pests. Previous studies have suggested that enhancement of CarE activity is an important mechanism mediating indoxacarb resistance in Spodoptera litura, and several CarE genes have been found to be overexpressed in indoxacarb-resistant strains. However, the functions of these CarE genes in indoxacarb resistance needs to be further investigated.

RESULTS

The synergist triphenyl phosphate effectively reduced the resistance of S. litura to indoxacarb, suggesting an involvement of CarEs in indoxacarb resistance. Among seven identified S. litura CarE genes (hereafter SlituCOE), six were overexpressed in two indoxacarb-resistant strains, but there were no significant differences in gene copy number. Knockdown of SlituCOE009 and SlituCOE050 enhanced indoxacarb sensitivity in both susceptible and resistant strains, whereas knockdown of SlituCOE090, SlituCOE093 and SlituCOE074 enhanced indoxacarb sensitivity in only the resistant strain. Knockdown of the sixth gene, SlituCOE073, did not have any effect. Furthermore, simultaneous knockdown of the five SlituCOE genes had a greater effect on increasing indoxacarb sensitivity than silencing them individually. By contrast, overexpression of the five SlituCOE genes individually in Drosophila melanogaster significantly decreased the toxicity of indoxacarb to transgenic fruit flies. Furthermore, modeling and docking analysis indicated that the catalytic pockets of SlituCOE009 and SlituCOE074 were ideally shaped for indoxacarb and N-decarbomethoxylated metabolite (DCJW), but the binding affinity for DCJW was stronger than for indoxacarb.

CONCLUSION

This study reveals that multiple overexpressed CarE genes are involved in indoxacarb resistance in S. litura.

Resistance Monitoring for Six Insecticides in Vegetable Field-Collected Populations of Spodoptera litura from China

The common cutworm, Spodoptera litura (Fabricius), is a notorious and damaging insect pest of horticultural crops in China, the management of which largely relies on chemical agents that are limited by the development of chemical resistance in target populations. As such, resistance monitoring of S. litura populations is a necessary part of management strategies of insecticide resistance. In the current work, we monitored resistance to six insecticides in field-collected populations of S. litura sampled from eleven provinces across China in 2021. The results show that S. litura populations developed significant resistance against chlorantraniliprole, cyantraniliprole, metaflumizone, and pyridalyl and low levels of resistance to chromafenozide. However, S. litura populations were susceptible or exhibited minimal resistance to tetraniliprole. Possible cross-resistances between chlorantraniliprole, cyantraniliprole, metaflumizone, pyridalyl, and chromafenozide were found by pairwise correlation, which also revealed that tetraniliprole lacked cross-resistance with all insecticides tested. Our results suggest suspending the use of chemical agents against which S. litura displayed significant field-evolved resistance, such as chlorantraniliprole, metaflumizone, and pyridalyl, in favor of pesticides against which S. litura was susceptible or exhibited minimal resistance, such as tetraniliprole and chromafenozide, which may help slow the development of insecticide resistance, and in which field management programs aimed at controlling S. litura in China would benefit from the integration of such survey-informed insecticide application strategies. Moreover, the baseline susceptibility confirmed for the six tested insecticides can contribute to design strategies of resistance management for S. litura.

Toxicity of Ribavirin to Spodoptera litura by Inhibiting the Juvenile Hormone

Ribavirin is an antiviral drug showing high and delayed toxicity to the destructive agricultural pest Spodoptera litura. Larvae fed with artificial diets containing ribavirin could not molt successfully and showed abnormal phenotypes, including cuticle melanization and heavy wrinkle of the newly formed procuticle. RNA-Seq analysis suggested that ribavirin has great negative influence on cuticle. Quantitative real-time-polymerase chain reaction results indicated that ribavirin treatment decreased the expression of key genes in juvenile hormone (JH) biosynthesis (CYP15C1 and JH acid methyltransferase) and most cuticle protein genes, whereas the genes in melanin biosynthesis and bursicon genes were upregulated by ribavirin treatment. These results coincided with the decreased titer of JH I, JH II, and JH III determined by enzyme-linked immunosorbent assay, the much thinner procuticle layer exhibited by histopathological examination, and the cuticle melanization after ribavirin treatment. These results provided a valuable theoretical basis for the creation of green insecticides targeting JH and the development of new insecticide derivatives from 1,2,4-triazole.

Neuroligin 3 from common cutworm enhances the GABA-induced current of recombinant SlRDL1 channel

BACKGROUND

Neuroligin (NLG) protein is a nerve cell adhesion molecule and plays a key role in the precision apposition of presynaptic domains on inhibitory and excitatory synapses. Existing studies mainly focused on the function of NLG3 against the excitatory channel. However, the interaction between insect NLG3 and ionotropic GABA receptor, which is the main inhibitory channel, remains unclear. In this study, the Nlg3 of common cutworm (CCW), Spodoptera litura Fabricius, one important agricultural Lepidopteron, is selected to explore its function in the inhibitory channel.

RESULTS

The SlNlg3 was obtained and the SlNLG3 contains the characteristic features including transmembrane domain, PDZ-binding motif and type-B carboxylesterases signature 2 motif. The SlNlg3 messenger RNA (mRNA) was most abundant in midgut, and exhibited multiple expression patterns in different developmental stages and tissues or body parts. Compared with the single injection of SlRDL1, the median effective concentration value of GABA in activating currents was smaller in Xenopus laevis oocytes co-injected with SlRDL1 and SlNlg3. In addition, SlNlg3 could enhance the GABA-induced current of homomeric SlRDL1 channel from -391.86 ± 15.41 to -2152.51 ± 30.09 nA. DsSlNlg3 depressed the expression level of SlNlg3 mRNA more than 64.29% at 6 h. After exposure to median lethal dose of fluralaner, the mortality of CCW injected with dsSlNlg3 was significantly decreased by 13.34% and 30.00% at 24 and 48 h, respectively, compared to injection of dsEGFP.

CONCLUSION

NLG3 should have physiological function on ionotropic GABA receptor in vitro, which provided a favorable foundation for further research on the physiological function of Nlg gene in Lepidopteron. © 2021 Society of Chemical Industry.

The role of Glutathione-S-transferases in phoxim and chlorfenapyr tolerance in a major mulberry pest, Glyphodes pyloalis walker (Lepidoptera: Pyralidae)

Glyphodes pyloalis Walker is a destructive pest on mulberry trees and poses a significant threat to the sericultural industry in China. Phoxim and chlorfenapyr are two commonly used insecticides in mulberry fields. Glutathione-S-transferases (GSTs) comprise a multifunctional protein superfamily that plays important roles in the detoxification of insecticides and xenobiotic compounds in insects. However, whether GSTs participate in the tolerance of phoxim and chlorfenapyr in G. pyloalis is still unknown. To better understand the mechanism of insecticide tolerance in G. pyloalis, the enzymatic activity of GSTs was evaluated under phoxim and chlorfenapyr exposure, respectively. GST enzyme activity was significantly increased after 12, 36 and 48 h of phoxim treatment and 12, 24, 36 and 48 h of chlorfenapyr treatment. Subsequently, eighteen GST genes were identified from the larvae transcriptome of G. pyloalis. Among these, ten GpGSTs had GSH-binding sites and fifteen GpGSTs had variable hydrophobic substrate-binding sites. The expression levels of Delta-GpGST and Epsilon-GpGST genes were significantly influenced by phoxim and chlorfenapyr treatment, and by the time post insecticide application. Furthermore, after silencing GpGST-E4, the mortality rate of G. pyloalis larvae was increased when they were exposed to chlorfenapyr, but it did not significantly alter when the larvae were exposed to phoxim. Our results indicated the vital roles of GpGSTs in the tolerance of insecticides and this action depends on the categories of insecticides. The present study provides a theoretical basis for elucidating insecticide susceptibility and promotes functional research on GST genes in G. pyloalis.

SlGSTE9 participates in the stability of chlorpyrifos resistance in Spodoptera litura

BACKGROUND

Spodoptera litura is an important agricultural pest and has developed serious resistance to multiple insecticides. The resistance level to several insecticides is reported to be unstable, but the mechanism is less reported.

RESULTS

Chlorpyrifos and phoxim resistance level in a field-collected population of S. litura declined continuously from the first to the tenth generation and remained stable at the 11th and 12th generations without insecticide exposure. Synergist experiment showed that diethyl maleate and piperonyl butoxide significantly increased mortality to chlorpyrifos and phoxim in the first and sixth generations, but not in the 12th generation. The expression of 31 identified glutathione S-transferase (GST) genes in the third-instar larvae of S. litura in the first, sixth and 12th generations was determined, and eight genes were seen to decrease significantly in the sixth and 12th generations compared with the first generation. SlGSTe9 was selected for further functional study as it had higher abundance and significantly higher expression in the chlorpyrifos-resistant population than in the susceptible population. The recombinant protein of SlGSTE9 showed metabolism activity to chlorpyrifos in vitro and in Escherichia coli, but not to phoxim. Silencing of SlGSTe9 increased the cumulative mortality to chlorpyrifos significantly. SlGSTE9 also showed antioxidant activity to cumene hydroperoxide.

CONCLUSION

Our results suggest that SlGSTe9 is directly involved in chlorpyrifos resistance stability, but not in phoxim. SlGSTE9 may also participate in insecticides resistance by relieving the oxidase stress induced by insecticides. © 2021 Society of Chemical Industry.

Protective effects of agrimonolide on hypoxia-induced H9c2 cell injury by maintaining mitochondrial homeostasis

Cardiomyocyte death caused by hypoxia is one of the main causes of myocardial infarction or heart failure, and mitochondria play an important role in this process. Agrimonolide (AM) is a monomeric component extracted from Agrimonia pilosa L. and has antioxidant, antitumor, and anti-inflammatory effects. This study aimed to investigate the role and mechanism of AM in improving hypoxia-induced H9c2 cell damage. The results showed that low AM concentrations promote H9c2 cell proliferation and increase cellular ATP content. Transcriptome sequencing showed that AM induces differential expression of genes in H9c2 cells. Gene ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed that these genes were concentrated in mitochondrial function. Subsequent experiments confirmed that AM regulates hypoxia-induced cell cycle arrest. AM inhibited the rate of apoptosis by regulating the expression of apoptosis-related proteins, reducing the level of cleaved Caspase 3 and Bax, and increasing the level of Bcl2, thereby protecting H9c2 cells from hypoxia-induced apoptosis. AM restored the mitochondrial membrane potential, inhibited the generation of ROS, maintained the normal shape of the mitochondria, improved the level of the mitochondrial functional proteins OPA1, MFN1, MFN2, Tom20, and increased the level of ATP. In conclusion, AM protects H9c2 cells from hypoxia-induced cell damage.

Functional analysis of CYP6AE68, a cytochrome P450 gene associated with indoxacarb resistance in Spodoptera litura (Lepidoptera: Noctuidae)

Spodoptera litura (Fabricius) is a widely distributed, highly polyphagous pest that can cause severe damage to a variety of economically important crops. Various populations have developed resistance to different classes of insecticides. In this study, we report on two indoxacarb-resistant S. litura populations, namely Ind-R (resistance ratio = 18.37-fold) derived from an indoxacarb-susceptible (Ind-S) population and a population caught from a field (resistance ratio = 46.72-fold). A synergist experiment showed that piperonyl butoxide (PBO) combined with indoxacarb produced higher synergistic effects (synergist ratio = 5.29) in the Ind-R population as compared to Ind-S (synergist ratio = 3.08). Elevated enzyme activity of cytochrome P450 monooxygenases (P450s) was observed for Ind-R (2.15-fold) and the Field-caught population (4.03-fold) as compared to Ind-S, while only minor differences were noticed in the activities of esterases and glutathione S-transferases. Furthermore, expression levels of P450 genes of S. litura were determined by quantitative reverse transcription PCR to explore differences among the three populations. The results showed that the mRNA levels of CYP6AE68, a novel P450 gene belonging to the CYP6 family, were constitutively overexpressed in Ind-R (32.79-fold) and in the Field-caught population (68.11-fold). CYP6AE68 expression in S. litura was further analyzed for different developmental stages and in different tissues. Finally, we report that RNA interference-mediated silencing of CYP6AE68 increased the mortality of fourth-instar larvae exposed to indoxacarb at the LC₅₀ dose level (increase by 33.89%, 29.44% and 22.78% for Ind-S, Ind-R and the Field-caught population, respectively). In conclusion, the findings of this study indicate that expression levels of CYP6AE68 in S. litura larvae are associated with indoxacarb resistance and that CYP6AE68 may play a significant role in detoxification of indoxacarb.

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.

Gene selection for studying frugivore-plant interactions: a review and an example using Queensland fruit fly in tomato

Fruit production is negatively affected by a wide range of frugivorous insects, among them tephritid fruit flies are one of the most important. As a replacement for pesticide-based controls, enhancing natural fruit resistance through biotechnology approaches is a poorly researched but promising alternative. The use of quantitative reverse transcription PCR (RT-qPCR) is an approach to studying gene expression which has been widely used in studying plant resistance to pathogens and non-frugivorous insect herbivores, and offers a starting point for fruit fly studies. In this paper, we develop a gene selection pipe-line for known induced-defense genes in tomato fruit, Solanum lycopersicum, and putative detoxification genes in Queensland fruit fly, Bactrocera tryoni, as a basis for future RT-qPCR research. The pipeline started with a literature review on plant/herbivore and plant/pathogen molecular interactions. With respect to the fly, this was then followed by the identification of gene families known to be associated with insect resistance to toxins, and then individual genes through reference to annotated B. tryoni transcriptomes and gene identity matching with related species. In contrast for tomato, a much better studied species, individual defense genes could be identified directly through literature research. For B. tryoni, gene selection was then further refined through gene expression studies. Ultimately 28 putative detoxification genes from cytochrome P450 (P450), carboxylesterase (CarE), glutathione S-transferases (GST), and ATP binding cassette transporters (ABC) gene families were identified for B. tryoni, and 15 induced defense genes from receptor-like kinase (RLK), D-mannose/L-galactose, mitogen-activated protein kinase (MAPK), lipoxygenase (LOX), gamma-aminobutyric acid (GABA) pathways and polyphenol oxidase (PPO), proteinase inhibitors (PI) and resistance (R) gene families were identified from tomato fruit. The developed gene selection process for B. tryoni can be applied to other herbivorous and frugivorous insect pests so long as the minimum necessary genomic information, an annotated transcriptome, is available.

Transcriptional response of detoxifying enzyme genes in Bombyx mori under chlorfenapyr exposure

The silkworm, Bombyx mori (B. mori) is an important economic insect which ingests mulberry leaves and products the silk in industry. Chlorfenapyr is a new halogenated pyrrole insecticide which has been promoted for the control of mulberry insect pests in China. However, the detoxification mechanism of the silkworm to chlorfenapyr has not been investigated yet. In the present study, we first estimated the LC₃₀ dose of chlorfenapyr for 3rd instar B. mori larvae, and then, in order to characterise the chlorfenapyr detoxification mechanism, the transcriptomes of chlorfenapyr-treated and untreated 3rd instar B. mori larvae were compared using RNA-sequencing. In total, 146, 533, 126 and 148, 957, 676 clean reads were obtained from insecticide-treated and control silkworm larvae, respectively, and these reads generated 10, 954 genes. The transcriptional profile of silkworm larvae was significantly influenced by chlorfenapyr treatment. A total of 1196 differentially expressed genes (DEGs) were identified in insecticide-treated and control B. mori larvae, in which 644 genes were upregulated and 552 genes were downregulated. Results showed that multiple DEGs were enriched in detoxication-related gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Eleven detoxifying enzyme genes which differentially expressed were screened, and their expression patterns were validated by qRT-PCR. Furthermore, we successfully knocked down all differentially upregulated detoxifying enzyme genes, and a bioassay showed that the mortality of chlorfenapyr-treated silkworm larvae was significantly higher after silencing these genes than in groups injected with dsGFP. The present study reveals the molecular basis of silkworm detoxification to chlorfenapyr exposure, and provides new insights into the management of insecticide damage in the silkworm.

Resistance in the Genus Spodoptera: Key Insect Detoxification Genes

The genus Spodoptera (Lepidoptera: Noctuidae) includes species that are among the most important crop pests in the world. These polyphagous species are able to feed on many plants, including corn, rice and cotton. In addition to their ability to adapt to toxic compounds produced by plants, they have developed resistance to the chemical insecticides used for their control. One of the main mechanisms developed by insects to become resistant involves detoxification enzymes. In this review, we illustrate some examples of the role of major families of detoxification enzymes such as cytochromes P450, carboxyl/cholinesterases, glutathione S-transferases (GST) and transporters such as ATP-binding cassette (ABC) transporters in insecticide resistance. We compare available data for four species, Spodoptera exigua, S. frugiperda, S. littoralis and S. litura. Molecular mechanisms underlying the involvement of these genes in resistance will be described, including the duplication of the CYP9A cluster, over-expression of GST epsilon or point mutations in acetylcholinesterase and ABCC2. This review is not intended to be exhaustive but to highlight the key roles of certain genes.

Functional Analysis of SlGSTE12 in Pyrethroid and Organophosphate Resistance in Spodoptera litura

Glutathione S-transferase genes in the epsilon group were reported to function in insecticide resistance. SlGSTE12 was validated to be overexpressed in pyrethroid- and organophosphate-resistant populations of Spodoptera litura compared to a susceptible population. A functional study of heterologously expressed SlGSTE12 showed that K_m and V_max for 1-chloro-2,4-dinitrobenzene (CDNB) conjugating activity were 0.70 ± 0.18 mmol L^-1 and 90.6 ± 9.4 nmol mg^-1 min^-1, respectively. β-Cypermethrin and cyhalothrin showed much weaker inhibition of SlGSTE12 activity to CDNB conjugation than fenvalerate, chlorpyrifos, and phoxim. Ultrahigh-performance liquid chromatography analysis showed that SlGSTE12 had significant metabolism activity to fenvalerate and phoxim both in vitro and in Escherichia coli, especially to chlorpyrifos, and slight metabolism activity toward cyhalothrin only in vitro. Silencing of SlGSTE12 by RNAi increased the mortality to fenvalerate, cyhalothrin, and chlorpyrifos significantly. SlGSTE12 also had a significant antioxidant ability against cumene hydroperoxide. Our study suggested that SlGSTE12 could metabolize phoxim, fenvalerate, cyhalothrin, and especially chlorpyrifos. SlGSTE12 might also participate in pyrethroid and organophosphate resistance by antioxidant activity.

Evaluation of Sensitivity to Phoxim and Cypermethrin in an Endoparasitoid, Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae), and Its Parasitization Efficiency Under Insecticide Stress

Insecticides can have consequences for beneficial arthropods. Insect parasitoids can contact insecticides through direct exposure spray droplets or residues on crop foliage. Here, we focus on better understand the response of Meteorus pulchricornis (Wesmael), a parasitoid wasp of lepidopteran pests, and its detoxification mechanisms on stress caused by phoxim and cypermethrin. Hence, we determined the dose-mortality curves and estimating the sublethal concentrations (LC30 and LC50). Then, we applied the sublethal concentrations against adult parasitoids to assess its survival, parasitism efficacy, and also developmental and morphometric parameters of their offspring. Simultaneously, we check the activities of glutathione S-transferase (GST), acetylcholinesterase (AChE), and peroxidase (POD) after sublethal exposure of both insecticides, which has measured until 48 h after treatment. Overall, phoxim and cypermethrin exhibited acute lethal activity toward the parasitoid with LC50 values 4.608 and 8.570 mg/liter, respectively. Also, we detect that LC30 was able to trigger the enzymatic activity of GST, AChE, and POD, suggesting a potential detoxification mechanism. However, even when subjected to sublethal exposure, our results indicate strong negatives effects, in particular for phoxim, which has affected the parasitism efficacy and also the developmental and morphometric parameters of M. pulchricornis offspring. Therefore, it can be concluded that both phoxim and cypermethrin have negative impacts on M. pulchricornis and we suggest cautioning their use and the need for semifield and field assessments to confirm such an impact.