STAT5B, Akt and p38 Signaling Activate FTZ-F1 to Regulate the Xenobiotic Tolerance-Related Gene SlCyp9a75b in Spodoptera litura.

Cytochrome P450 monooxygenases in insects have been verified to implicated in insecticide and phytochemical detoxification metabolism. However, the regulation of P450s, which are modulated by signal-regulated transcription factors (TFs), is less well studied in insects. Here, we found that the Malpighian tubule specific P450 gene SlCYP9A75b in Spodoptera litura is induced by xenobiotics. The transgenic Drosophila bioassay and RNAi results indicated that this P450 gene contributes to α-cypermethrin, cyantraniliprole, and nicotine tolerance. In addition, functional analysis revealed that the MAPKs p38, PI3K/Akt, and JAK-STAT activate the transcription factor fushi tarazu factor 1 (FTZ-F1) to regulate CYP9A75b expression. These findings provide mechanistic insights into the contributions of CYP9A genes to xenobiotic detoxification and support the possible involvement of different signaling pathways and TFs in tolerance to xenobiotics in insects.

The Fat Body-Specific GST Gene SlGSTe11 Enhances the Tolerance of Spodoptera litura to Cyantraniliprole and Nicotine.

Spodoptera litura is a significant agricultural pest, and its glutathione S-transferase (GST) plays a crucial role in insecticide resistance. This study aimed to investigate the relationship between the SlGSTe11 gene of S. litura and resistance to cyantraniliprole and nicotine. Transcriptome analysis revealed that SlGSTe11 is highly expressed mainly in fat bodies, with a significant increase in SlGSTe11 gene expression under induction by cyantraniliprole and nicotine. The ectopic expression of the SlGSTe11 gene in transgenic fruit flies resulted in a 5.22-fold increase in the tolerance to cyantraniliprole. Moreover, compared to the UAS-SlGSTe11 line, the Act5C-UAS>SlGSTe11 line laid more eggs and had a lower mortality after nicotine exposure. RNAi-mediated inhibition of SlGSTe11 gene expression led to a significant increase in the mortality of S. litura under cyantraniliprole exposure. In vitro metabolism experiments demonstrated that the recombinant SlGSTe11 protein efficiently metabolizes cyantraniliprole. Molecular docking results indicated that SlGSTe11 has a strong affinity for both cyantraniliprole and nicotine. These findings suggest that SlGSTe11 is involved in the development of resistance to cyantraniliprole and nicotine in S. litura.

Implications of cypermethrin exposure on population dynamics and fitness traits of laboratory-selected resistant and susceptible populations of Spodoptera litura (Fabricius).

The tobacco cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) is an economically important agricultural polyphagous pest worldwide. It has shown high resistance to several insecticides, including cypermethrin, a synthetic pyrethroid that is used in large-scale commercial agricultural applications. The present study investigated the development of selection-induced resistance to cypermethrin and associated fitness costs in S. litura. After continuous exposure to cypermethrin for consecutive fifteen generations, the cypermethrin-selected population (CYP-Sel) of S. litura developed a 21.2-fold resistance. The CYP-Sel strain had a relative fitness of 0.16 when treated with LC50, prolonged larval duration, and development time. Meanwhile, the strain also showed shorter adult duration, lower fecundity, and hatchability compared with the Unsel-Lab population. CYP-Sel population showed a significant disadvantage in intrinsic rate of natural increase (rm), net reproductive rate (Ro), and finite rate of increase (λ) when compared to the Unsel-Lab population. This knowledge could help to design resistance management strategies against this particular pest, along with potential management strategies to overcome the development of resistance.

Exposure to toxic cadmium concentration induce physiological and molecular mechanisms alleviating herbivory infestation in Wedelia.

Cadmium (Cd) toxicity induces significant disruptions in growth and development, plants have developed strategies to alleviate metal toxicity promoting establishment even during herbivores infestation. The study demonstrates that W. trilobata maintains growth and development under the combined stress of Cd exposure and herbivore invasion by Spodoptera litura, in contrast to W. chinensis. Cd toxicity markedly reduce shoot elongation and total fresh biomass, and a significant decrease in the dry weight of the shoot biomass and leaf count by 19%, 18%, 16%, and 19% in W. trilobata compared to controls. An even more pronounced decrease of 35%, 43%, 45% and 43% was found in W. chinensis. Compared to W. chinensis, W. trilobata showed a higher increase in phytohormone production including abscisic acid (ABA), gibberellic acid (GA3), indole-3-acetic acid (IAA) and methyl jasmonic acid (JA-me) under both Cd and herbivory stress as compared with respective controls. In addition, leaf ultra-structure also showed the highest damage to cell membranous structures by Cd-toxicity in W. chinensis. Furthermore, RNA-seq analysis revealed numerous genes viz., EMSY, MCCA, TIRI, BED-type, ABA, JAZ, CAB-6, CPSI, LHCII, CAX, HNM, ABC-Cd-trans and GBLP being differentially expressed between Cd-stress and herbivory groups in both W. trilobata and W. chinensis, with a particular emphasis on genes associated with metal transport and carbohydrate metabolism. Analyses employing the Gene Ontology (GO) system, the Clusters of Orthologous Groups (COG) categorization, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, highlight the functional and evolutionary relationships among the genes of the Phenylpropanoid and Flavonoid biosynthesis pathways and brassinosterod metabolism, associated with plant growth and development under Cd-toxicity and herbivory. W. trilobata opposite of W. chinensis, significantly improve plant growth and mitigates Cd toxicity through modulation of metabolic processes, and regulation of responsible genes, to sustain its growth under Cd and herbivory stress, which can be used in stress improvement in plants for sustainable ecosystem biodiversity and food security.

Insecticidal potential and risk assessment of diamide pesticides against Spodoptera frugiperda in maize crops.

The effectiveness, tolerance, and safety of pesticides must be established before their scientific or rational. This study evaluates the field control efficacy of broflanilide, tetraniliprole, and chlorantraniliprole in combating Spodoptera frugiperda in maize crops, as well as the resistance of S. frugiperda to these three diamide pesticides after exposure. By assessing field control efficiency, toxicity, effects on development and reproduction, and detoxification enzyme activity of these diamide pesticides on S. frugiperda, highlights broflanilide's significant insecticidal potential. A highly sensitive and efficient method using QuEChERS/HPLCMS/MS was developed to simultaneously detect residues of these three pesticides on maize. Initial concentrations of broflanilide, tetraniliprole, and chlorantraniliprole ranged from 2.13 to 4.02 mg/kg, with their respective half-lives varying between 1.23 and 1.51 days. Following foliar application, by the time of harvest, the terminal residue concentrations of these pesticides were all under 0.01 mg/kg. Chronic dietary intake risk assessments and cumulative chronic dietary exposure for three pesticides indicated that the general population's terminal residue concentration was within acceptable limits. Not only does this research provide valuable insights into field control efficiency, insecticidal effects, resistance, residues, and risk assessment results of broflanilide, tetraniliprole, and chlorantraniliprole on maize, but additionally, it also paves the way for setting suitable Maximum Residue Limits (MRLs) values based on pre-harvest interval values, rational dosage, and application frequency.

Jasmonic Acid and Salicylic Acid improved resistance against Spodoptera frugiperda Infestation in maize by modulating growth and regulating redox homeostasis.

Exploring host plant resistance and elevating plant defense mechanisms through the application of exogenous elicitors stands as a promising strategy for integrated pest management. The fall armyworm, a pernicious menace to grain crops in tropical and subtropical regions, stands as a formidable threat due to its capacity for devastation and a wide-ranging spectrum of host plants. There is no literature regarding artificially induced resistance in maize against fall armyworm (Spodoptera frugiperda) by exogenous application of phytohormones. The present investigation was performed to evaluate the role of jasmonic acid (JA) and salicylic acid (SA) on two maize hybrids namely FH-1046 and YH-1898 against fall armyworm. Results showed that plant height, biomass and lengths, fresh and dry weight of root shoot which decreased with armyworm infestation improved with phytohormonal application. JA treatment resulted in a higher increase in all attributes as compared to SA treatment. Improvement in relative water contents, photosynthetic pigments and pronounced levels of phenol and proline accumulation were observed in infested plants after JA treatment. Infested plants recovered from oxidative stress as JA application activated and increased the antioxidant enzyme activity of superoxide dismutase, peroxidase and polyphenol oxidase activity in both FH-1046 and YH-1898 . The oxidative stress reduction in infested plants after JA treatment was also evident from a fair decrease in MDA and H2O2 in both varieties. The SA and JA mediated genes expression was studied and it was found that in FH1046 maize cultivar, JA dependent genes, particularly marker genes PR1 and Lox5 were highly expressed along with TPS10 and BBT12. Whereas SPI, WRKY28, ICS and PAL were shown to be activated upon SA application. Evidently, both JA and SA elicited a robust defensive response within the maize plants against the voracious S. frugiperda, which in consequence exerted a discernible influence over the pest's developmental trajectory and physiological dynamics. A decrease in detoxification enzyme activity of the insects was observed after feeding on treated plants. Moreover, it was recorded that the survival and weight gain of FAW feeding on phytohormone treated maize plants also decelerated. In conclusion, FH-1046 was found to be more tolerant than YH-1898 against fall armyworm infestation and 1 mM JA was more effective than 1 mM SA for alleviation of fall armyworm stress. Therefore, it was inferred that phytohormones regulated redox homeostasis to circumvent oxidative damage and mediate essential metabolic events in maize under stress. To our current understanding, this study is the very first presentation of induced resistance in maize against S. frugiperda with the phytohormonal application (JA and SA).

High nitrogen application in maize enhances insecticide tolerance of the polyphagous herbivore Spodoptera litura by induction of detoxification enzymes and intensification of cuticle.

Nitrogen (N) is one of the most intensively used fertilizers in cropping system and could exert a variety of bottom-up effects on the ecological fitness of herbivores. However, the effects of increased N inputs on insect pesticide tolerance have not been comprehensively understood. Bioassays showed that high N (HN) applied to maize plants significantly increased larval tolerance of Spodoptera litura to multiple insecticides. Activities of detoxification enzymes were significantly higher in the larvae fed on maize plants supplied with HN. RNA-seq analysis showed that numerous GST and cuticle-related genes were induced in the larvae fed on HN maize. RT-qPCR analysis further confirmed four GST genes and larval-specific cuticle gene LCP167. Furthermore, when injected with dsRNA specific to GSTe1, GSTs5, and LCP167, the mortality of larvae treated with methomyl was about 3-fold higher than that of dsGFP-injected larvae. Electron microscope observation showed that cuticle of the larvae fed on HN maize was thicker than the medium level of N. These findings suggest that increased application of N fertilizer enhances insecticide tolerance of lepidopteran pests via induction of detoxification enzymes and intensification of cuticle. Thus, overuse of N fertilizer may increase pest insecticide tolerance and usage of chemical insecticides.

A novel spider venom peptide from the predatory mite Neoseiulus barkeri shows lethal effect on phytophagous pests.

The long-term use of pesticides in the field, and the high fertility and adaptability of phytophagous mites have led to resistance problems; consequently, novel safe and efficient active substances are necessary to broaden the tools of pest mite control. Natural enemies of arthropods typically secrete substances with paralytic or lethal effects on their prey, and those substances are a resource for future biopesticides. In this study, two putative venom peptide genes were identified in a parasitic mite Neoseiulus barkeri transcriptome. Recombinant venom NbSP2 peptide injected into Tetranychus cinnabarinus mites was significantly more lethal than recombinant NBSP1. NbSP2 was also lethal to Spodoptera litura when injected but not when fed to third instar larvae. The interaction proteins of NbSP2 in T. cinnabarinus and S. litura were identified by affinity chromatography. Among these proteins, ATP synthase subunit ß (ATP SSß) was deduced as a potential target. Four binding sites were predicted between NBSP2 and ATP SSß of T. cinnabarinus and S. litura. In conclusion, we identified a venom peptide with activity against T. cinnabarinus and S. litura. This study provides a novel component for development of a new biological pesticide.

Cadmium and phthalate impacts developmental growth and mortality of Spodoptera littoralis, but not reproductive success.

Our environment is increasingly polluted with various molecules, some of which are considered endocrine disruptors. Metals and phthalates, originating from industrial activities, agricultural practices, or consumer products, are prominent examples of such pollutants. We experimentally investigated the impacts of the heavy metal cadmium and the phthalate DEHP on the moth Spodoptera littoralis. More specifically, larvae were reared in laboratory conditions, where they were exposed to diets contaminated with either two doses of cadmium at concentrations of 62.5 µg/g or 125 µg/g, two doses of DEHP at 100 ng/g and 10 µg/g, or a combination of both low and high doses of the two compounds, with a control group for comparison. Our findings indicate that cadmium delays the developmental transition from larva to adult. Notably, the combination of cadmium and DEHP exacerbated this delay, highlighting a synergistic effect. In contrast, DEHP alone did not affect larval development. Additionally, we observed that cadmium exposure, both alone and in combination with DEHP, led to a lower mass at all larval stages. However, cadmium-exposed individuals that reached adulthood eventually reached a similar mass to those in other groups. Interestingly, while our results did not show any effect of the treatments on hatching success, there was a higher adult mortality rate in the cadmium-treated groups. This suggests that while moths may prioritize reproductive success, their survival at the adult stage is compromised by cadmium exposure. In conclusion, our study demonstrates the impact of cadmium on the development, mass, and adult survival of moths, and reveals synergistic effects when combined with DEHP. These results confirm cadmium as an endocrine disruptor, even at low doses. These insights underscore the importance of understanding the toxicological effects of low doses of pollutants like cadmium and DEHP, both individually and in combination.

Tetraniliprole risk assessment: Unveiling a hidden threat for managing a generalist herbivore.

Insecticide resistance poses a significant challenge in managing generalist herbivores such as the tobacco cutworm (TCW), Spodoptera litura. This study investigates the potential risks associated with using the novel diamide insecticide tetraniliprole to control TCW. A tetraniliprole-resistant strain was developed through twelve generations of laboratory selection, indicating an intermediate risk of resistance development. Field monitoring in China revealed a significant incidence of resistance, particularly in the Nanchang (NC) population (>100-fold). Tetraniliprole showed moderate to high cross-resistance to multiple insecticides and was autosomally inherited with incomplete dominance, controlled by multiple genes, some of which belong to the cytochrome P450 family associated with enhanced detoxification. Life table studies indicated transgenerational hormesis, stimulating TCW female fecundity and increasing population net reproduction rates (R0). These findings suggest a potential for pest resurgence under tetraniliprole use. The integrated risk assessment provides a basis for the sustainable management of TCW using tetraniliprole.

Sublethal effect and detoxifying metabolism of metaflumizone and indoxacarb on the fall armyworm, Spodoptera frugiperda.

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera, Noctuidae), is a highly polyphagous invasive pest that damages various crops. Pesticide control is the most common and effective strategy to control FAW. In this study, we evaluated the toxicity of metaflumizone and indoxacarb against third-instar FAW larvae using the insecticide-incorporated artificial diet method under laboratory conditions. Both metaflumizone and indoxacarb exhibited substantial toxicity against FAW, with LC50 values of 2.43 and 14.66 mg/L at 72 h, respectively. The sublethal effects of metaflumizone and indoxacarb on parental and F1 generation FAW were investigated by exposing third-instar larvae to LC10 and LC30 concentrations of these insecticides. Sublethal exposure to these two insecticides significantly shortened adult longevity, extended pupal developmental times and led to reduced pupal weight, pupation rates, and adult fecundity in the treated parental generation and F1 generation at LC10 or LC30 concentrations, in comparison to the control group. The larval developmental times were shortened in the parental generation but prolonged in the F1 generation, after being treated with sublethal concentrations of metaflumizone. Furthermore, larvae exposed to LC10 or LC30 concentrations of indoxacarb exhibited elevated activity levels of cytochrome P450 monooxygenase and glutathione S-transferase, which coincides with the observed synergistic effect of piperonyl butoxide and diethyl maleate. In conclusion, the high toxicity and negative impact of metaflumizone and indoxacarb on FAW provided significant implications for the rational utilization of insecticides against this pest.

Phytometabolites from coral jasmine flower extracts: Toxic effects on Spodoptera litura and enzyme inhibition in nontarget earthworm Eisenia fetida as an alternative approach.

Green pesticides, derived from natural sources, have gained wider attention as an alternative to synthetic pesticides for managing polyphagous pests, such as Spodoptera litura. In this study, the methanolic flower extract of Nyctanthes arbor-tristis (Mx-Na-t) was subjected to chemical screening, and 3-hydroxy-1,2-dimethyl-4(1H)-pyridone (3H-dp) and tyrosol (Ty-ol) were identified as the major derivatives. The toxic effects of Mx-Na-t (500 ppm) were highest in third-instar S. litura larvae (96.4%), while those of 3H-dp and Ty-ol (5 ppm) were highest in second-instar larvae (76.5% and 81.4%, respectively). The growth and development of S. litura larvae and pupae were significantly reduced by all three treatments. Fecundity rates were also reduced by all treatments [from 1020 eggs (control) to 540 eggs by Mx-Na-t treatment, 741 eggs by 3H-dp treatment, and 721 eggs by Ty-ol treatment]. The extract and its active constituents decreased adult emergence and slowed total larval development in a dose-dependent manner. A decrease was noted in the major gut enzymes of young S. litura larvae exposed to Mx-Na-t, 3H-dp, and Ty-ol. Moreover, midgut tissues of fourth-instar larvae were severely damaged by Mx-Na-t (250 ppm), 3H-dp (2.5 ppm), and Ty-ol (2.5 ppm); the treatments induced structural damage to the epithelial cells and gut lumen. The earthworm Eisenia fetida was used to assess nontarget toxicity. Compared with cypermethrin, the phytochemicals exhibited minimal effects on the earthworm's detoxifying enzymes superoxide dismutase and catalase after 14 days of treatment. Moreover, in silico predictions using BeeTox and ProTox-II indicated little or no toxicity of 3H-dp and Ty-ol toward honey bees and other nontarget species.

Towards Sustainable Pest Management: Toxicity, Biochemical Effects, and Molecular Docking Analysis of Ocimum basilicum (Lamiaceae) Essential Oil on Agrotis ipsilon and Spodoptera littoralis (Lepidoptera: Noctuidae).

Over the last decade, essential oils (EOs) have become potential ingredients for insecticide formulations due to their widespread availability and perceived safety. Therefore, this study aimed to evaluate the toxicity and biochemical efficacy of basil (Ocimum basilicum) (Lamiaceae) against two destructive pests Noctuidae, Agrotis ipsilon (Hufnagel) and Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). In addition, a molecular docking study was performed to gain insight into the binding pattern between glutathione S-transferase (GST) and linalool, the main component of EO. GC-MS analysis of O. basilicum EO revealed that linalool is the most abundant compound (29.34%). However, the toxicity tests showed no significant difference between the values of LC50 of O. basilicum EO to A. ipsilon and S. littoralis. On the other hand, the sublethal experiments indicated that treating the second instar larvae with LC15 or LC50 values of O. basilicum EO significantly prolonged the larval duration in both insects, compared to the control. Regarding the biochemical effect of O. basilicum EO, the treatments significantly impacted the activity of detoxification enzymes. A notable elevation in glutathione S-transferase (GST) activity was recorded in A. ipsilon larvae compared with a reduction in S. littoralis larvae. The molecular docking analysis revealed that linalool bonded with the amino acid serine (SER 9) of GST, indicating its binding affinity with the enzyme. The obtained results could offer valuable insights into the mode of action of O. basilicum and can encourage the adoption of sustainable pest control practices that incorporate essential oils.

Synergistic effects of chlorantraniliprole and camptothecin on physiological impairments, histopathological, biochemical changes, and genes responses in the larvae midgut of Spodoptera frugiperda.

Spodoptera frugiperda is an economically important agricultural pest and poses a serious threat to food security globally. Its management is gravely challenged by its high polyphagous nature, strong migratory ability, and massive fecundity. Chlorantraniliprole (CHL) is widely utilized in controlling S. frugiperda, its intensive application and over-reliance pose adverse health risks, development of resistance, toxicity to beneficial insects, natural enemies, and environmental contamination. To address S. frugiperda resistance to CHL and its inherent challenges, this study explores the synergistic effects of camptothecin (CPT) with CHL in its management. The binary mixed adversely induced the larvae weight and mortality when compared to single-treated. CHL + CPT (1:20 mg/L) had the highest larvae mortality of (73.80 %) with a high antagonistic factor (0.90), while (1:10 mg/L) with (66.10%) mortality exhibited a high synergistic factor (1.43). Further, CHL + CPT (1:10 mg/L) considerably altered the midgut epithelial cell, peritrophic membrane, microvilli, basement membrane, and regenerative cells. For biochemical analysis, CHL + CPT (1:10 mg/L) significantly decreased glutathione-S-transferase (1-chloro-2,4-dinitrobenzene CDNB) and cytochrome P450 (7-ethoxycoumarin O-deethylation) activities in the midgut in a dose and time dependent manner. Based on RNA-Seq analysis, a total of 4,373 differentially expressed genes (DEGs) were identified from the three treatments. CPT vs CK (Control) had 1694 (968 up-, 726 down-regulated), CHL vs CK with 1771 (978 up-, 793 down-regulated), and CHL + CPT vs CK had 908 (394 up-, 514 down-regulated) DEGs. The enrichment analysis disclosed significant pathways such as metabolism of xenobiotics by cytochrome P450, glutathione metabolism, TOLL and IMD (Immune Deficiency) signaling pathway, longevity regulating pathway. This study provides basis to expatiate on the molecular toxicological mechanism of CHL + CPT in management of fall armyworm.

Design, synthesis and biological activities of echinopsine derivatives containing acylhydrazone moiety.

Based on the broad-spectrum biological activities of echinopsine and acylhydrazones, a series of echinopsine derivatives containing acylhydrazone moieties have been designed, synthesized and their biological activities were evaluated for the first time. The bioassay results indicated that most of the compounds showed moderate to good antiviral activities against tobacco mosaic virus (TMV), among which echinopsine (I) (inactivation activity, 49.5 ± 4.4%; curative activity, 46.1 ± 1.5%; protection activity, 42.6 ± 2.3%) and its derivatives 1 (inactivation activity, 44.9 ± 4.6%; curative activity, 39.8 ± 2.6%; protection activity, 47.3 ± 4.3%), 3 (inactivation activity, 47.9 ± 0.9%; curative activity, 43.7 ± 3.1%; protection activity, 44.6 ± 3.3%), 7 (inactivation activity, 46.2 ± 1.6%; curative activity, 45.0 ± 3.7%; protection activity, 41.7 ± 0.9%) showed higher anti-TMV activity in vivo at 500 mg/L than commercial ribavirin (inactivation activity, 38.9 ± 1.4%; curative activity, 39.2 ± 1.8%; protection activity, 36.4 ± 3.4%). Some compounds exhibited insecticidal activities against Plutella xylostella, Mythimna separate and Spodoptera frugiperda. Especially, compounds 7 and 27 displayed excellent insecticidal activities against Plutella xylostell (mortality 67 ± 6% and 53 ± 6%) even at 0.1 mg/L. Additionally, most echinopsine derivatives exhibited high fungicidal activities against Physalospora piricola and Sclerotinia sclerotiorum.

Toxicity of Bioactive Molecule Andrographolide against Spodoptera litura Fab and Its Binding Potential with Detoxifying Enzyme Cytochrome P450.

Spodoptera litura Fab. is a polyphagous pest causing damage to many agriculture crops leading to yield loss. Recurrent usage of synthetic pesticides to control this pest has resulted in resistance development. Plant-derived diterpenoid compound andrographolide was isolated from the leaves of Andrographis paniculata. It was analysed by gas chromatography-mass spectroscopy and quantified by HPLC. Nutritional indices and digestive enzymatic profile were evaluated. Third, fourth and fifth instar larvae were treated with different concentrations of andrographolide. At 3, 6 and 9 ppm-treated concentrations the larvae showed decreased RGR, RCR, ECI, ECD values with adverse increase in AD. The digestive enzymes were significantly inhibited when compared with control. Conspicuously, andrographolide showed pronounced mortality of S. litura by inhibition of enzyme secretion and intake of food. The binding ability of andrographolide with CYTP450 showed high affinity with low binding energy. Andrographolide has the potential to be exploited as a biocontrol agent against S. litura as an eco-friendly pesticide.

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

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

Role of digestive protease enzymes and related genes in host plant adaptation of a polyphagous pest, Spodoptera frugiperda.

The evolutionary success of phytophagous insects depends on their ability to efficiently exploit plants as a source of energy for survival. Herbivorous insects largely depend on the efficiency, flexibility, and diversity of their digestive physiology and sophistication of their detoxification system to use chemically diverse host plants as food sources. The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a polyphagous pest of many commercially important crops. To elucidate the ability of this insect pest to adapt to host plant mechanisms, we evaluated the impact of primary (corn) and alternate (rice) host plants after 11 generations on gut digestive enzymatic activity and expression profiles of related genes. Results indicated that the total protease and class-specific trypsin- and chymotrypsin-like protease activity of S. frugiperda significantly differed among host plant treatments. The class-specific protease profiles greatly differed in S. frugiperda midguts upon larval exposure to different treatments with inhibitors compared with treatments without inhibitors. Similarly, the single and cumulative effects of the enzyme-specific inhibitors TLCK, TPCK, and E-64 significantly increased larval mortality and reduced larval growth/mass across different plant treatments. Furthermore, the quantitative reverse transcription polymerase chain reaction results revealed increased transcription of two trypsin (SfTry-3, SfTry-7) and one chymotrypsin gene (Sfchym-9), which indicated that they have roles in host plant adaptation. Knockdown of these genes resulted in significantly reduced mRNA expression levels of the trypsin genes. This was related to the increased mortality observed in treatments compared with the dsRED control. This result indicates possible roles of S. frugiperda gut digestive enzymes and related genes in host plant adaptation.

Gene expression of PLAT and ATS3 proteins increases plant resistance to insects.

MAIN CONCLUSION: Genes of the PLAT protein family, including PLAT and ATS3 subfamilies of higher plants and homologs of liverwort, are involved in plant defense against insects. Laticifer cells in plants contain large amounts of anti-microbe or anti-insect proteins and are involved in plant defense against biotic stresses. We previously found that PLAT proteins accumulate in laticifers of fig tree (Ficus carica) at comparable levels to those of chitinases, and the transcript level of ATS3, another PLAT domain-containing protein, is highest in the transcriptome of laticifers of Euphorbia tirucalli. In this study, we investigated whether the PLAT domain-containing proteins are involved in defense against insects. Larvae of the lepidopteran Spodoptera litura showed retarded growth when fed with Nicotiana benthamiana leaves expressing F. carica PLAT or E. tirucalli ATS3 genes, introduced by agroinfiltration using expression vector pBYR2HS. Transcriptome analysis of these leaves indicated that ethylene and jasmonate signaling were activated, leading to increased expression of genes for PR-1, ß-1,3-glucanase, PR5 and trypsin inhibitors, suggesting an indirect mechanism of PLAT- and ATS3-induced resistance in the host plant. Direct cytotoxicity of PLAT and ATS3 to insects was also possible because heterologous expression of the corresponding genes in Drosophila melanogaster caused apoptosis-mediated cell death in this insect. Larval growth retardation of S. litura occurred when they were fed radish sprouts, a good host for agroinfiltration, expressing any of nine homologous genes of dicotyledon Arabidopsis thaliana, monocotyledon Brachypodium distachyon, conifer Picea sitchensis and liverwort Marchantia polymorpha. Of these nine genes, the heterologous expression of A. thaliana AT5G62200 and AT5G62210 caused significant increases in larval death. These results indicated that the PLAT protein family has largely conserved anti-insect activity in the plant kingdom (249 words).

Potential insecticidal activity of aminonaphthoquinone Mannich bases derived from lawsone and their copper (II) complex derivatives.

The fall armyworm, Spodoptera frugiperda, is a polyphagous pest that causes important damage in different regions of America and mainly affects corn crops in both tropical and subtropical areas. Currently, control relies on both transgenic plants and/or chemical pesticides. In this work, we describe insecticidal activity against the fall armyworm from a series of Mannich bases (1-10), derived from 2-hydroxy-1,4-naphthoquinone (lawsone), substituted benzaldehydes, and two primary amines, and their Cu2+ complexes (11-20). The [Cu(L)2] complexes were more effective in larval mortality compared to the free Mannich bases. Among the tested compounds, complex 11 showed the highest toxicity, with 70.00% larval mortality.