Spodoptera frugiperda Sf9 cells as a model system to investigate the role of detoxification gene expression in response to xenobiotics

Cd Exposure Confers Cross-Tolerance of Hyphantria cunea Larvae to β-Cypermethrin through miRNA-Mediated Post-Transcriptional Regulation

Heavy metals are prevalent environmental contaminants in pest habitats. This study investigates the tolerance of Hyphantria cunea larvae to β-cypermethrin under cadmium (Cd) stress. Exposure to Cd markedly enhanced larval tolerance to β-cypermethrin. The P450 enzyme was found to be crucial in triggering this cross-tolerance. Notably, Cd exposure significantly upregulated the expression of HcCYP333A29 and HcCYP6AE184 both before and after β-cypermethrin treatment. Silencing these genes reduced the β-cypermethrin tolerance in Cd-exposed larvae. Furthermore, overexpression of HcCYP333A29 and HcCYP6AE184 significantly improved the tolerance of Sf9 cells and Drosophila to β-cypermethrin. Silencing of HcDicer-1, a key gene in the miRNA synthesis pathway, significantly diminished the β-cypermethrin tolerance in Cd-treated larvae. The miR-2739 controlled overexpression of HcCYP333A29, while miR-2854 controlled HcCYP6AE184 overexpression, both of which were essential for β-cypermethrin cross-tolerance in H. cunea larvae under Cd exposure. Collectively, Cd exposure induces cross-tolerance to β-cypermethrin in H. cunea larvae through miRNA-mediated post-transcriptional regulation.

Divergent Selection Promotes Intraspecific Genomic Differentiation in Spodoptera littoralis With Possible Involvement in Detoxification

The cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae), is a major agricultural pest affecting crops like cotton, maize, tomatoes, and wheat across southern Europe, Africa, the Middle East, and western Asia. Whole genome analyses have revealed adaptive evolution in chemosensation and detoxification genes in S. littoralis. However, the extent of intraspecific diversity influenced by recent adaptive evolutionary forces remains unclear. In this study, we conducted a population genomics analysis using 31 S. littoralis individuals from sub-Saharan Africa, northern Africa, and southern Europe to assess the existence of intraspecific population divergence and identify the underlying evolutionary forces. We show whole genome differentiation between populations based on geographic origin from the analyzed samples. Phylogenetic analyses indicate that sub-Saharan and southern European populations share a common ancestor, distinct from several northern African populations. FST and dXY statistics along the chromosomes reveal loci with restricted gene flow among populations. These loci are associated with population-specific selective sweeps, indicating the role of divergent natural selection in limiting gene flow. Notably, these loci are enriched with detoxification genes, including cytochrome P450, multidrug resistance, and xanthine dehydrogenase genes, all of which are potentially associated with detoxification. These results demonstrate that divergent selection limits gene flow among geographically distinct populations with the possibility of the involvement of detoxification as a key trait. We argue that this genetic heterogeneity can be considered in pest monitoring and management, as strategies tailored to specific populations may not be relevant for others.

Investigating the role of the ROS/CncC-xenobiotics signaling pathway in the response to Fenpropathrin in Cyprinus carpio lymphocytes: Involving lipid peroxidation and Fe2+ metabolism imbalance

Fenpropathrin (FPT) is a synthetic pyrethroid insecticide, the persistence and accumulation in water of which could cause harmful effects on vulnerable groups like aquatic creatures, particularly posing significant risks to fish immune systems. This study aimed to investigate how environmentally relevant FPT concentrations (10-1000 μ/M) affect lipid peroxidation and Fe2+ metabolism in Cyprinus carpio head kidney lymphocytes, and its relationship with oxidative stress and immunotoxicity. Firstly, CCK-8 results demonstrated that FPT caused a significant increase in lymphocyte death. Secondly, lymphocytes exposed to FPT could lead ferroptosis in lymphocytes, accompanied by evidence of the Fe2+ transporter imbalance, lipid peroxidation, Fe2+ accumulation and ferroptosis related protein increment. Thirdly, we found that FPT esposure leads to a decrease in ATP, mitochondrial DNA and NADPH/NADP+ levels, and the mRNA associated with mitochondrial function-related genes (Fis1, Drp1, and OPA1) in lymphocytes. Additionally, FPT induced the increased the levels of inflammatory genes (TNF-α, IFN-γ, and IL-6) in head kidney lymphocytes. Importantly, exposure to FPT induced oxidative stress to produce intracellular ROS, disrupting the function of the CncC signaling pathway and expression disorder of xenobiotics detoxification (CYP 450 family) genes. Notably, Treatment with NAC (a ROS inhibitor, 5 μM) demonstrated that inhibiting ROS alleviated FPT-induced lymphocyte ferroptosis and inflammatory response via the ROS/CncC-xenobiotics signaling pathway. These findings not only introduces a novel approach to investigating the immunotoxicity of FPT but also offers critical insights into mitigating the adverse effects of FPT on aquatic animal health.

Effect of Benzyl Alcohol on Main Defense System Components of Galleria mellonella (Lepidoptera)

Benzyl alcohol (E1519) is an aromatic alcohol used in the pharmaceutical and food industry. It is used to protect food products against microorganisms during storage, as a flavoring in the production of chocolate and confectionery products, as an important ingredient in fragrance, and as a preservative in medical products. However, little is known of its effect on insects. The main aim of this study was to determine the influence of benzyl alcohol on the defense systems of the wax moth Galleria mellonella, i.e., its cuticular lipid composition and critical elements of its immune system. A gas chromatography/mass spectrometry (GC/MS) analysis found benzyl alcohol treatment to elicit significant quantitative and qualitative differences in cuticular free fatty acid (FFA) profiles. Our findings indicate that benzyl alcohol treatment increased the levels of HSP70 and HSP90 and decreased those of HSF1, histamine, and cysteinyl leukotriene. Benzyl alcohol application also increased dismutase level in the hemolymph and lowered those of catalase and 8-OHdG. The treatment also had negative effects on G. mellonella hemocytes and a Sf9 cell line in vitro: 48-h treatment resulted in morphological changes, with the remaining cells being clearly spindle-shaped with numerous granules. The high insecticidal activity of compound and its lack of toxicity towards vertebrates suggest it could be an effective insecticide.

Screening and functional validation of the core detoxification genes conferring broad-spectrum response to insecticides in Spodoptera frugiperda

BACKGROUND

Fall armyworm, Spodoptera frugiperda, a formidable agricultural pest, has developed resistance to various synthetic insecticides. However, how S. frugiperda utilizes its limited energy and resources to deal with various insecticides remains largely unexplored.

RESULTS

We utilized transcriptome sequencing to decipher the broad-spectrum adaptation mechanism of S. frugiperda to eight insecticides with distinct modes-of-action. Analysis of the Venn diagram revealed that 1014 upregulated genes and 778 downregulated genes were present in S. frugiperda treated with at least five different insecticides, compared to the control group. Exposure to various insecticides led to the significant upregulation of eight cytochrome P450 monooxygenases (P450s), four UDP glucosyltransferases (UGTs), two glutathione-S-transferases (GSTs) and two ATP-binding cassette transporters (ABCs). Among them, the sfCYP340AD3 and sfCYP4G74 genes were demonstrated to respond to stress from six different insecticides in S. frugiperda, as evidenced by RNA interference and toxicity bioassays. Furthermore, homology modeling and molecular docking analyses showed that sfCYP340AD3 and sfCYP4G74 possess strong binding affinities to a variety of insecticides.

CONCLUSION

Collectively, these findings showed that S. frugiperda utilizes a battery of core detoxification genes to cope with the exposure of synthetic insecticides. This study also sheds light on the identification of efficient insecticidal targets gene and the development of resistance management strategies in S. frugiperda, thereby facilitating the sustainable control of this serious pest. © 2024 Society of Chemical Industry.

Functional orthologs of honeybee CYP6AQ1 in stingless bees degrade the butenolide insecticide flupyradifurone

Flupyradifurone (FPF), a novel butenolide insecticide binding to nicotinic acetylcholine receptors (nAChRs), has been shown to be less acutely toxic to western honey bees (Apis mellifera) than other insecticides such as neonicotinoids sharing the same target-site. A previous study revealed that this is due to enhanced oxidative metabolism of FPF, mediated by three cytochrome P450 monooxygenases (P450s), including CYP6AQ1. Therefore, we followed a toxicogenomics approach and investigated the potential role of functional CYP6AQ1 orthologs in FPF metabolism from eight different bee species, including stingless bees (Tribe: Meliponini). We conducted a phylogenetic analysis on four stingless bee species, including Frieseomelitta varia, Heterotrigona itama, Melipona quadrifasciata and Tetragonula carbonaria to identify CYP6AQ1-like functional orthologs. Three non-Meliponini, but tropical bee species, i.e., Ammobates syriacus, Euglossa dilemma and Megalopta genalis were analyzed as well. We identified candidate P450s in all (neo)tropical species with greater than 61% and 67% predicted protein sequence identities when compared to A. mellifera CYP6AQ1 and Bombus terrestris CYP6AQ26, respectively. Heterologous expression in High Five insect cells of these functional orthologs revealed a common coumarin substrate profile and a preference for the O-debenzylation of bulkier substrates. Competition assays using the fluorescent probe substrate 7-benzyloxymethoxy-4-trifluoromethylcoumarin (BOMFC) with these enzymes indicated inhibition of BOMFC metabolism by increasing concentrations of FPF. Furthermore, UPLC-MS/MS analysis revealed the capacity of all CYP6AQ1-like orthologs to metabolize FPF by hydroxylation in vitro at various levels, indicating a conserved FPF detoxification potential in different (neo)tropical bee species including Meliponini. This research, employing a toxicogenomics approach, provides important insights into the potential of stingless and other tropical bee species to detoxify FPF, and highlights the significance of investigating the detoxification mechanisms of insecticides in non-Apis bee species by molecular tools to inform risk assessment and conservation efforts.

Investigating the role of the ROS/CncC signaling pathway in the response to xenobiotics in Spodoptera frugiperda using Sf9 cells

Spodoptera frugiperda (fall armyworm, FAW) is an invasive polyphagous lepidopteran pest that has developed sophisticated resistance mechanisms involving detoxification enzymes to eliminate toxic compounds it encounters in its diet including insecticides. Although its inventory of detoxification enzymes is known, the mechanisms that enable an adapted response depending on the toxic compound remain largely unexplored. Sf9 cells were used to investigate the role of the transcription factors, Cap n' collar isoform C (CncC) and musculoaponeurotic fibrosarcoma (Maf) in the regulation of the detoxification response. We overexpressed CncC, Maf or both genes, and knocked out (KO) CncC or its repressor Kelch-like ECH associated protein 1 (Keap1). Joint overexpression of CncC and Maf is required to confer increased tolerance to indole 3-carbinol (I3C), a plant secondary metabolite, and to methoprene, an insecticide. Both molecules induce reactive oxygen species (ROS) pulses in the different cell lines. The use of an antioxidant reversed ROS pulses and restored the tolerance to I3C and methoprene. The activity of detoxification enzymes varied according to the cell line. Suppression of Keap1 significantly increased the activity of cytochrome P450s, carboxylesterases and glutathione S-transferases. RNAseq experiments showed that CncC mainly regulates the expression of detoxification genes but is also at the crossroads of several signaling pathways (reproduction and immunity) maintaining homeostasis. We present new data in Sf9 cell lines suggesting that the CncC:Maf pathway plays a central role in FAW response to natural and synthetic xenobiotics. This knowledge helps to better understand detoxification gene expression and may help to design next-generation pest insect control measures.

Identification and characterization of candidate detoxification genes in Pharsalia antennata Gahan (Coleoptera: Cerambycidae)

The wood-boring beetles, including the majority of Cerambycidae, have developed the ability to metabolize a variety of toxic compounds derived from host plants and the surrounding environment. However, detoxification mechanisms underlying the evolutionary adaptation of a cerambycid beetle Pharsalia antennata to hosts and habitats are largely unexplored. Here, we characterized three key gene families in relation to detoxification (cytochrome P450 monooxygenases: P450s, carboxylesterases: COEs and glutathione-S-transferases: GSTs), by combinations of transcriptomics, gene identification, phylogenetics and expression profiles. Illumina sequencing generated 668,701,566 filtered reads in 12 tissues of P. antennata, summing to 100.28 gigabases data. From the transcriptome, 215 genes encoding 106 P450s, 77 COEs and 32 GSTs were identified, of which 107 relatives were differentially expressed genes. Of the identified 215 genes, a number of relatives showed the orthology to those in Anoplophora glabripennis, revealing 1:1 relationships in 94 phylogenetic clades. In the trees, P. antennata detoxification genes mainly clustered into one or two subfamilies, including 64 P450s in the CYP3 clan, 33 COEs in clade A, and 20 GSTs in Delta and Epsilon subclasses. Combining transcriptomic data and PCR approaches, the numbers of detoxification genes expressed in abdomens, antennae and legs were 188, 148 and 141, respectively. Notably, some genes exhibited significantly sex-biased levels in antennae or legs of both sexes. The findings provide valuable reference resources for further exploring xenobiotics metabolism and odorant detection in P. antennata.