ABSTRACT
The time that elapsed between the initial introduction and the proliferation of an invasive species is referred to as the lag phase. The identification of the lag phase is critical for generating plans for pest management and for the prevention of biosecurity failure. However, lag phases have been identified mostly through retrospective searches of historical records. The agricultural pest fall armyworm (FAW; Spodoptera frugiperda) is native to the New World. FAW invasion was first reported from West Africa in 2016, then it spread quickly through Africa, Asia, and Oceania. Here, using population genomics approaches, we demonstrate that the FAW invasion involved an undocumented lag phase. Invasive FAW populations have negative signs of genomic Tajima's D, and invasive population-specific genetic variations have particularly decreased Tajima's D, supporting a substantial amount of time for the generation of new mutations in introduced FAW populations. Model-based diffusion approximations support the existence of a period with a cessation of gene flow between native and invasive FAW populations. Taken together, these results provide strong support for the presence of a lag phase during the FAW invasion. These results show the usefulness of using population genomics analyses to identify lag phases in biological invasions.
Subject(s)
Introduced Species , Spodoptera , Animals , Spodoptera/genetics , Genetic Variation , Gene Flow , Genetics, Population , Metagenomics , Genomics/methodsABSTRACT
Genetically modified (GM) crops, expressing Bacillus thuringiensis (Bt) insecticidal toxins, have substantially transformed agriculture. Despite rapid adoption, their environmental and economic benefits face scrutiny due to unsustainable agricultural practices and the emergence of resistant pests like Spodoptera frugiperda, known as the fall armyworm (FAW). FAW's adaptation to Bt technology in corn and cotton compromises the long-term efficacy of Bt crops. To advance the understanding of the genetic foundations of resistance mechanisms, we conducted an exploratory comparative transcriptomic analysis of two divergent FAW populations. One population exhibited practical resistance to the Bt insecticidal proteins Cry1A.105 and Cry2Ab2, expressed in the genetically engineered MON-89Ø34 - 3 maize, while the other population remained susceptible to these proteins. Differential expression analysis supported that Cry1A.105 and Cry2Ab2 significantly affect the FAW physiology. A total of 247 and 254 differentially expressed genes were identified in the Cry-resistant and susceptible populations, respectively. By integrating our findings with established literature and databases, we underscored 53 gene targets potentially involved in FAW's resistance to Cry1A.105 and Cry2Ab2. In particular, we considered and discussed the potential roles of the differentially expressed genes encoding ABC transporters, G protein-coupled receptors, the P450 enzymatic system, and other Bt-related detoxification genes. Based on these findings, we emphasize the importance of exploratory transcriptomic analyses to uncover potential gene targets involved with Bt insecticidal proteins resistance, and to support the advantages of GM crops in the face of emerging challenges.
Subject(s)
Bacillus thuringiensis Toxins , Bacterial Proteins , Endotoxins , Hemolysin Proteins , Insecticide Resistance , Spodoptera , Transcriptome , Spodoptera/drug effects , Spodoptera/genetics , Animals , Endotoxins/genetics , Endotoxins/pharmacology , Hemolysin Proteins/genetics , Hemolysin Proteins/pharmacology , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Insecticide Resistance/genetics , Plants, Genetically Modified/genetics , Plants, Genetically Modified/parasitology , Zea mays/genetics , Zea mays/parasitology , Gene Expression ProfilingABSTRACT
BACKGROUND: Energy homeostasis is vital for insects to survive food shortages. This study investigated the starvation tolerance of Spodoptera frugiperda, which invaded China in 2019, focusing on its storage protein family, crucial for energy balance. 10 storage protein family members were identified and their expression patterns at different development stages and under different starvation stress were analyzed. METHODS AND RESULTS: We used qPCR to evaluate the expression levels of storage protein family members under various larval instars and starvation conditions. We discovered that, among above 10 members, only 2 storage proteins, SfSP8 and SfSP7 showed significant upregulation in response to starvation stress. Notably, SfSP8 upregulated markedly after 24 h of fasting, whereas SfSP7 exhibited a delayed response, with significant upregulation observed only after 72 h of starvation. Then we significantly reduced the starvation tolerance of larvae through RNAi-mediated knockdown of SfSP8 and also altered the starvation response of SfSP7 from a late to an early activation pattern. Finally, we constructed transgenic Drosophila melanogaster with heterologous overexpressing SfSP8 revealed that the starvation tolerance of the transgenic line was significantly stronger than that of wild-type lines. CONCLUSIONS: SfSP8 was the core storage protein member that mediated the starvation tolerance of larvae of S. frugiperda. Our study on the novel function of storage proteins in mediating larval starvation tolerance of S. frugiperda is conducive to understanding the strong colonization of this terrible invasive pest.
Subject(s)
Insect Proteins , Larva , Spodoptera , Starvation , Animals , Spodoptera/genetics , Larva/genetics , Larva/metabolism , Starvation/genetics , Insect Proteins/genetics , Insect Proteins/metabolism , Drosophila melanogaster/genetics , Drosophila melanogaster/metabolism , Animals, Genetically Modified , Stress, Physiological/geneticsABSTRACT
Natalisin (NTL) is a conserved neuropeptide, only present in insects, that has been reported to regulate their sexual activity. In this study, we investigated the involvement of NTL in the reproductive behaviors of a major invasive pest, Spodoptera frugiperda. We identified NTL precursor-encoded transcripts, and evaluated their transcript levels in different stages and tissues of S. frugiperda. The results showed that the NTL transcript level was expressed in both male and female pupae and both male and female adults in the later stage. It was highly expressed in male pupae, 3-day-old male and female adults, and 5-day-old male adults. In different tissues, the expression level is higher in the male and female adult brain and male testis. Immunohistochemical staining of the brain of S. frugiperda female and male adults revealed that three pairs of brain neurons of S. frugiperda adults of both sexes secreted and expressed NTL. To study the role of NTL in reproductive behaviors, NTL was silenced in S. frugiperda male and female adults by RNA interference (RNAi) technology, the results showed that silencing NTL could significantly affect the sexual activity behavior of the adults, reducing the calling rate of females, the courtship rate of males, and the mating rate. In summary, this study emphasizes the important role of NTL in regulating the mating behavior and sexual activity of S. frugiperda in both male and female adults, potentially laying a foundation to employ NTL as a new insect-specific target to control populations of pest insects.
Subject(s)
Neuropeptides , Sexual Behavior, Animal , Spodoptera , Animals , Spodoptera/genetics , Spodoptera/physiology , Male , Female , Neuropeptides/metabolism , Neuropeptides/genetics , Sexual Behavior, Animal/physiology , Insect Proteins/genetics , Insect Proteins/metabolism , Brain/metabolism , RNA Interference , ReproductionABSTRACT
Phytophagous insects are more predisposed to evolve insecticide resistance than other insect species due to the "preadaptation hypothesis". Cytochrome P450 monooxygenases have been strongly implicated in insecticide and phytochemical detoxification in insects. In this study, RNA-seq results reveal that P450s of Spodoptera litura, especially the CYP3 clan, are dominant in cyantraniliprole, nicotine, and gossypol detoxification. The expression of a Malpighian tubule-specific P450 gene, SlCYP9A75a, is significantly upregulated in xenobiotic treatments except α-cypermethrin. The gain-of-function and loss-of-function analyses indicate that SlCYP9A75a contributes to cyantraniliprole, nicotine, and α-cypermethrin tolerance, and SlCYP9A75a is capable of binding to these xenobiotics. This study indicates the roles of inducible SlCYP9A75a in detoxifying man-made insecticides and phytochemicals and may provide an insight into the development of cross-tolerance in omnivorous insects.
Subject(s)
Cytochrome P-450 Enzyme System , Insect Proteins , Insecticide Resistance , Insecticides , Malpighian Tubules , Spodoptera , Xenobiotics , Animals , Spodoptera/genetics , Spodoptera/drug effects , Spodoptera/enzymology , Insect Proteins/genetics , Insect Proteins/metabolism , Cytochrome P-450 Enzyme System/metabolism , Cytochrome P-450 Enzyme System/genetics , Xenobiotics/metabolism , Insecticides/pharmacology , Malpighian Tubules/metabolism , Malpighian Tubules/enzymology , Malpighian Tubules/drug effects , Insecticide Resistance/genetics , Inactivation, Metabolic/genetics , Larva/growth & development , Larva/genetics , Larva/drug effectsABSTRACT
Indoxacarb is a pivotal insecticide used worldwide to manage Spodoptera exigua, a devastating agricultural pest. This active compound plays a crucial role in resistance management strategies due to its distinctive mode of action. A field population of S. exigua (SH23) from Shanghai, China, exhibited significantly reduced susceptibility to indoxacarb, with a resistance ratio of 113.84-fold in biological assays. Following two rounds of laboratory screening with indoxacarb, the resistance of the new strain (SH23-S2) escalated steeply to 876.15-fold. Genetic analyses of both the SH23 and SH23-S2 strains demonstrated autosomal inheritance and incompletely dominant resistance patterns. Synergist assays indicated a minor role of detoxification enzymes (glutathione s-transferases and cytochrome P450) of SH23-S2 strain in this resistance, implicating target-site resistance as the primary mechanism. To explore the impact of target-site resistance, segment 1-6 of domain IV (IVS1-6) of the sodium channel in S. exigua was cloned, and the sequences from susceptible and indoxacarb-resistant S. exigua were compared. The V1848I mutation, linked to indoxacarb resistance in Plutella xylostella, Tuta absoluta and Liriomyza trifolii, was identified and strongly associated with the indoxacarb-resistant phenotype in the S. exigua SH23-S2 strain, whereas the F1845Y mutation was not detected. Furthermore, a molecular test for the V1848I mutation in field populations was created using an allele-specific PCR (AS-PCR). The discovery of indoxacarb resistance mutation and the creation of diagnostic tool will enable the early detection of indoxacarb resistance, which will facilitate the implementation of targeted resistance management strategies, ultimately delaying the proliferation of resistance.
Subject(s)
Insecticide Resistance , Insecticides , Mutation , Oxazines , Spodoptera , Animals , Spodoptera/drug effects , Spodoptera/genetics , Oxazines/pharmacology , Insecticide Resistance/genetics , Insecticides/pharmacology , Insect Proteins/geneticsABSTRACT
Fall armyworm, Spodoptera frugiperda (J. E. Smith), is a widely recognized global agricultural pest that has significantly reduced crop yields all over the world. S. frugiperda has developed resistance to various insecticides. Insect cytochrome P450 monooxygenases (CYPs or P450s) play an important role in detoxifying insecticides, leading to increased resistance in insect populations. However, the function of the specific P450 gene for lambda-cyhalothrin resistance in S. frugiperda was unclear. Herein, the expression patterns of 40 P450 genes in the susceptible and lambda-cyhalothrin-resistant populations were analyzed. Among them, CYP321A7 was found to be overexpressed in the resistant population, specifically LRS (resistance ratio = 25.38-fold) derived from a lambda-cyhalothrin-susceptible (SS) population and FLRS (a population caught from a field, resistance ratio = 63.80-fold). Elevated enzyme activity of cytochrome P450 monooxygenases (P450s) was observed for LRS (2.76-fold) and the FLRS (4.88-fold) as compared to SS, while no significant differences were observed in the activities of glutathione S-transferases and esterases. Furthermore, the knockdown of CYP321A7 gene by RNA interference significantly increased the susceptibility to lambda-cyhalothrin. Remarkably, the knockdown of CYP321A7 reduced the enzymatic activity of P450 by 43.7%, 31.9%, and 22.5% in SS, LRS, and FLRS populations, respectively. Interestingly, fourth-instar larvae treated with lambda-cyhalothrin at the LC30 dosage had a greater mortality rate due to RNA interference-induced suppression of CYP321A7 (with increases of 61.1%, 50.0%, and 45.6% for SS, LRS, and FLRS populations, respectively). These findings suggest a link between lambda-cyhalothrin resistance and continual overexpression of CYP321A7 in S. frugiperda larvae, emphasizing the possible importance of CYP321A7 in lambda-cyhalothrin detoxification in S. frugiperda.
Subject(s)
Cytochrome P-450 Enzyme System , Insecticide Resistance , Insecticides , Nitriles , Pyrethrins , Spodoptera , Animals , Pyrethrins/pharmacology , Pyrethrins/toxicity , Spodoptera/drug effects , Spodoptera/genetics , Nitriles/toxicity , Nitriles/pharmacology , Cytochrome P-450 Enzyme System/genetics , Cytochrome P-450 Enzyme System/metabolism , Insecticides/pharmacology , Insecticides/toxicity , Insecticide Resistance/genetics , Insect Proteins/genetics , Insect Proteins/metabolism , RNA Interference , Inactivation, Metabolic , Larva/drug effects , Larva/geneticsABSTRACT
Spodoptera frugiperda is a notorious invasive pest causing substantial yield losses of crops and has developed resistance to various types of insecticides. In this study, a cyantraniliprole-resistant strain, SfCYAN-R, was obtained from a susceptible strain, SfCYAN-S, after 13 generations of selection with cyantraniliprole. The fitness cost in SfCYAN-R strain was evaluated, and the putative resistance-related genes were explored by RNA-seq analysis. The results showed that SfCYAN-R strain developed 23.97-fold resistance to cyantraniliprole with the realistic heritability of 0.127. The development time of eggs, larvae, prepupae and pupae in SfCYAN-R strain was significantly prolonged than that in SfCYAN-S strain, but no difference in pupation rate, emergence rate and female fecundity was observed between SfCYAN-R and SfCYAN-S strains. Comparative gene expression analysis between SfCYAN-R and SfCYAN-S strains identified 776 significant differentially expressed genes (DEGs), among which several DEGs associated with xenobiotic metabolism were upregulated in SfCYAN-R strain. These results provide insights into the resistance mechanisms of cyantraniliprole and would be helpful for resistance management of S. frugiperda.
Subject(s)
Insecticide Resistance , Insecticides , Pyrazoles , Spodoptera , ortho-Aminobenzoates , Animals , Spodoptera/genetics , Spodoptera/drug effects , ortho-Aminobenzoates/pharmacology , Insecticide Resistance/genetics , Insecticides/pharmacology , Pyrazoles/pharmacology , Gene Expression Profiling , Transcriptome , Risk Assessment , Larva/genetics , Larva/drug effects , FemaleABSTRACT
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.
Subject(s)
Insecticides , Larva , Nitrogen , Spodoptera , Zea mays , Animals , Zea mays/genetics , Spodoptera/drug effects , Spodoptera/genetics , Nitrogen/metabolism , Insecticides/pharmacology , Insecticides/toxicity , Larva/drug effects , Insecticide Resistance/genetics , Fertilizers , Glutathione Transferase/metabolism , Glutathione Transferase/genetics , Inactivation, Metabolic , Herbivory/drug effectsABSTRACT
Spodoptera frugiperda is a significant global pest, and chlorantraniliprole (CAP) is extensively used in China for its control. Understanding CAP resistance in S. frugiperda is crucial for effective management of this pest. Field populations exhibited varying degrees of resistance to CAP (RR = 1.74-5.60-fold). After 10 generations of selection, the CAP-resistant strain developed over 10-fold resistance, with a realized heritability (h2) of 0.10. Genetic analysis reveals inheritance patterns as autosomal, incomplete recessive, and monofactorial. The CAP-resistant strain showed limited cross-resistance to lufenuron and tetrachlorantraniliprole, negative cross-resistance to spinetoram, and no observed cross-resistance to other insecticides. Biochemical analysis suggested that P450-mediated detoxification is the primary resistance mechanism, with 26 genes overexpressed in the CAP-resistant strain. Additionally, the knockdown of CYP4L13, CYP6B39, CYP6B40, and CYP4G74 significantly increased the sensitivity of the resistant larvae to CAP. These findings highlight the resistance risk of CAP in S. frugiperda and emphasize the crucial role of P450 enzymes in resistance.
Subject(s)
Cytochrome P-450 Enzyme System , Insect Proteins , Insecticide Resistance , Insecticides , Larva , Spodoptera , ortho-Aminobenzoates , Spodoptera/drug effects , Spodoptera/genetics , Animals , ortho-Aminobenzoates/pharmacology , Insecticide Resistance/genetics , Insecticides/pharmacology , Insect Proteins/genetics , Insect Proteins/metabolism , Larva/drug effects , Larva/growth & development , Larva/genetics , Cytochrome P-450 Enzyme System/genetics , Cytochrome P-450 Enzyme System/metabolism , ChinaABSTRACT
Background: Spodoptera frugiperda, the fall armyworm is a destructive invasive pest, and S. litura the tobacco cutworm, is a native species closely related to S. frugiperda. The gut microbiota plays a vital role in insect growth, development, metabolism and immune system. Research on the competition between invasive species and closely related native species has focused on differences in the adaptability of insects to the environment. Little is known about gut symbiotic microbe composition and its role in influencing competitive differences between these two insects. Methods: We used a culture-independent approach targeting the 16S rRNA gene of gut bacteria of 5th instar larvae of S. frugiperda and S. litura. Larvae were reared continuously on maize leaves for five generations. We analyzed the composition, abundance, diversity, and metabolic function of gut microbiomes of S. frugiperda and S. litura larvae. Results: Firmicutes, Proteobacteria, and Bacteroidetes were the dominant bacterial phyla in both species. Enterococcus, ZOR0006, Escherichia, Bacteroides, and Lactobacillus were the genera with the highest abundance in S. frugiperda. Enterococcus, Erysipelatoclostridium, ZOR0006, Enterobacter, and Bacteroides had the highest abundance in S. litura. According to α-diversity analysis, the gut bacterial diversity of S. frugiperda was significantly higher than that of S. litura. KEGG analysis showed 15 significant differences in metabolic pathways between S. frugiperda and S. litura gut bacteria, including transcription, cell growth and death, excretory system and circulatory system pathways. Conclusion: In the same habitat, the larvae of S. frugiperda and S. litura showed significant differences in gut bacterial diversity and community composition. Regarding the composition and function of gut bacteria, the invasive species S. frugiperda may have a competitive advantage over S. litura. This study provides a foundation for developing control strategies for S. frugiperda and S. litura.
Subject(s)
Gastrointestinal Microbiome , Larva , RNA, Ribosomal, 16S , Spodoptera , Animals , Gastrointestinal Microbiome/genetics , Spodoptera/microbiology , Spodoptera/genetics , Larva/microbiology , RNA, Ribosomal, 16S/genetics , Proteobacteria/genetics , Proteobacteria/isolation & purification , Bacteroidetes/genetics , Bacteroidetes/isolation & purification , Firmicutes/genetics , Firmicutes/isolation & purification , Bacteria/genetics , Bacteria/classification , Lactobacillus/genetics , Lactobacillus/isolation & purification , Enterococcus/genetics , Bacteroides/genetics , SymbiosisABSTRACT
The evolution of resistance to insecticides poses a significant threat to pest management programs. Understanding the molecular mechanisms underlying insecticide resistance is essential to design sustainable pest control and resistance management programs. The fall armyworm, Spodoptera frugiperda, is an important insect pest of many crops and has a remarkable ability to evolve resistance to insecticides. In this study, we employed bulk segregant analysis (BSA) combined with DNA and RNA sequencing to characterize the molecular basis of spinetoram resistance in S. frugiperda. Analysis of genomic data derived from spinetoram selected and unselected bulks and the spinetoram-resistant and susceptible parental strains led to the identification of a three-nucleotide deletion in the gene encoding the nicotinic acetylcholine receptor α6 subunit (nAChR α6). Transcriptome profiling identified the upregulation of few genes encoding detoxification enzymes associated with spinetoram resistance. Thus, spinetoram resistance in S. frugiperda appears to be mediated mainly by target site insensitivity with a minor role of detoxification enzymes. Our findings provide insight into the mechanisms underpinning resistance to spinetoram in S. frugiperda and will inform the development of strategies to control this highly damaging, globally distributed crop pest.
Subject(s)
Insecticide Resistance , Insecticides , Spodoptera , Animals , Spodoptera/genetics , Spodoptera/drug effects , Insecticide Resistance/genetics , Insecticides/pharmacology , Insecticides/toxicity , Gene Expression Profiling , Transcriptome , Receptors, Nicotinic/genetics , Receptors, Nicotinic/metabolism , MacrolidesABSTRACT
Lambda-cyhalothrin, a representative pyrethroid insecticide widely used for Spodoptera frugiperda control in China, poses challenges due to the development of resistance. This study investigates the realized heritability, inheritance pattern, cross-resistance, and resistance mechanisms to lambda-cyhalothrin. After 21 generations of selection, the lambda-cyhalothrin-resistant strain (G21) developed a 171.11-fold resistance compared to a relatively susceptible strain (RS-G9), with a realized heritability (h2) of 0.11. Cross-resistance assays revealed that lambda-cyhalothrin-resistant strains showed no significant cross-resistance to the majority of tested insecticides. Genetic analysis indicated that lambda-cyhalothrin resistance in S. frugiperda was autosomal, incompletely dominant, and polygenic inheritance. The P450 enzyme inhibitor PBO significantly enhanced lambda-cyhalothrin toxicity in the resistant strains. Compared with the RS-G9 strain, the P450 enzyme activity was significantly increased and multiple P450 genes were significantly up-regulated in the lambda-cyhalothrin-resistant strains. RNAi targeting the most overexpressed P450 genes (CYP337B5 and CYP321B1) significantly increased the susceptibility of resistant S. frugiperda larvae to lambda-cyhalothrin. This study provides comprehensive insights into lambda-cyhalothrin resistance in S. frugiperda, and the results are helpful for developing effective resistance management strategies of this pest.
Subject(s)
Cytochrome P-450 Enzyme System , Insecticide Resistance , Insecticides , Nitriles , Pyrethrins , Spodoptera , Animals , Pyrethrins/pharmacology , Nitriles/pharmacology , Spodoptera/drug effects , Spodoptera/genetics , Insecticide Resistance/genetics , Insecticides/pharmacology , Cytochrome P-450 Enzyme System/genetics , Cytochrome P-450 Enzyme System/metabolism , RNA Interference , Larva/drug effects , Larva/geneticsABSTRACT
Like other lepidopteran insects, males of the tobacco cutworm moth, Spodoptera litura produce two kinds of spermatozoa, eupyrene (nucleate) and apyrene (anucleate) sperm. Formed in the testis, both kinds of sperm are released into the male reproductive tract in an immature form and are stored in the duplex region of the tract. Neither type of sperm is motile at this stage. When stored apyrene sperm from the duplex are treated in vitro with an extract of the prostatic region of the male tract, or with mammalian trypsin, they become motile; activation is greater and achieved more rapidly with increasing concentration of extract or enzyme. The activating effect of prostatic extract is blocked by soybean trypsin inhibitor (SBTI), also in a dose-dependent way. These results suggest that the normal sperm-activating process is due to an endogenous trypsin-like protease produced in the prostatic region. Proteomic analysis of S. litura prostatic extracts revealed a Trypsin-Like Serine Protease, TLSP, molecular weight 27 kDa, whose 199-residue amino acid sequence is identical to that of a predicted protein from the S. litura genome and is highly similar to predicted proteins encoded by genes in the genomes of several other noctuid moth species. Surprisingly, TLSP is only distantly related to Serine Protease 2 (initiatorin) of the silkmoth, Bombyx mori, the only identified lepidopteran protein so far shown to activate sperm. TLSP has features typical of secreted proteins, probably being synthesized as an inactive precursor zymogen, which is later activated by proteolytic cleavage. cDNA was synthesized from total RNA extracted from the prostatic region and was used to examine TLSP expression using qPCR. tlsp mRNA was expressed in both the prostatic region and the accessory glands of the male tract. Injection of TLSP-specific dsRNA into adult males caused a significant reduction after 24 h in tlsp mRNA levels in both locations. The number of eggs laid by females mated to adult males that were given TLSP dsRNA in 10 % honey solution, and the fertility (% hatched) of the eggs were reduced. Injecting pupae with TLSP dsRNA caused the later activation of apyrene sperm motility by adult male prostatic extracts to be significantly reduced compared to controls. Exposure of S. litura pupae to ionizing radiation significantly reduced expression of tlsp mRNA in the prostatic part and accessory gland of irradiated males in both the irradiated generation and also in their (unirradiated) F1 progeny. The implications of these findings for the use of the inherited sterility technique for the control of S. litura and other pest Lepidoptera are discussed.
Subject(s)
Insect Proteins , Spermatozoa , Spodoptera , Animals , Male , Spodoptera/genetics , Spodoptera/enzymology , Insect Proteins/metabolism , Insect Proteins/genetics , Spermatozoa/radiation effects , RNA Interference , Amino Acid Sequence , Genitalia, Male/metabolism , Genitalia, Male/radiation effects , Proteomics , Serine Proteases/metabolism , Serine Proteases/genetics , Radiation, Ionizing , Serine Endopeptidases/metabolism , Serine Endopeptidases/genetics , TranscriptomeABSTRACT
Spodoptera litura commonly known as the cutworm, is among the most destructive lepidopteran pests affecting over 120 plants species. The powerful destructive nature of this lepidopteran is attributable to its high reproductive capacity. The testicular fusion that occurs during metamorphosis from larvae to pupa in S.litura positively influences the reproductive success of the offspring. In contrast, Bombyx mori, the silkworm, retains separate testes throughout its life and does not undergo this fusion process. Microscopic examination reveals that during testicular fusion in S.litura, the peritoneal sheath becomes thinner and more translucent, whereas in B.mori, the analogous region thickens. The outer basement membrane in S.litura exhibits fractures, discontinuity, and uneven thickness accompanied by a significant presence of cellular secretions, large cell size, increased vesicles, liquid droplets, and a proliferation of rough endoplasmic reticulum and mitochondria. In contrast, the testicular peritoneal sheath of B.mori at comparable developmental stage exhibits minimal change. Comparative transcriptomic analysis of the testicular peritoneal sheath reveals a substantial difference in gene expression between the two species. The disparity in differential expressed genes (DEGs) is linked to an enrichment of numerous transcription factors, intracellular signaling pathways involving Ca2+ and GTPase, as well as intracellular protein transport and signaling pathways. Meanwhile, structural proteins including actin, chitin-binding proteins, membrane protein fractions, cell adhesion, extracellular matrix proteins are predominantly identified. Moreover, the study highlights the enrichment of endopeptidases, serine proteases, proteolytic enzymes and matrix metalloproteins, which may play a role in the degradation of the outer membrane. Five transcription factors-Slforkhead, Slproline, Slcyclic, Slsilk, and SlD-ETS were identified, and their expression pattern were confirmed by qRT-PCR. they are candidates for participating in the regulation of testicular fusion. Our findings underscore significant morphological and trancriptomic variation in the testicular peritoneal sheath of S.litura compared to the silkworm, with substantial changes at the transcriptomic level coinciding with testicular fusion. The research provides valuable clues for understanding the complex mechanisms underlying this unique phenomenon in insects.
Subject(s)
Bombyx , Spodoptera , Testis , Transcriptome , Animals , Male , Spodoptera/genetics , Testis/metabolism , Transcriptome/genetics , Bombyx/genetics , Bombyx/metabolism , Larva/genetics , Larva/metabolism , Metamorphosis, Biological/genetics , Metamorphosis, Biological/physiologyABSTRACT
Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a global pest causing damage to several crops. However, its management using chemical control is a challenge due to its capacity to evolve resistance to insecticides. After 6 generations of selection with lambda-cyhalothrin, the LC50 for the insecticide-resistant strain (Lambda-Sel) was 486 ppm, higher than that of the field strain (FAW-MUL) (7.5 ppm), susceptible laboratory strain (Lab-PK) (0.46 ppm), and laboratory unselected strain (UNSEL) (5.26 ppm). Laboratory selection with lambda-cyhalothrin increased resistance from 16.3- to 1056.52-fold and 1.43- to 92.4-fold to lambda-cyhalothrin compared to Lab-PK and UNSEL strains, respectively. The selected strain of S. frugiperda (Lambda-Sel) presented low cross-resistance to chlorpyrifos, moderate to deltamethrin and indoxacarb, very low to spinosad, and no cross-resistance to emamectin benzoate. The realized heritability (h2) of lambda-cyhalothrin resistance in the Lambda-Sel strain was very high (0.88). The reciprocal cross progenies of F1 (Lambda-Sel ââ ×â Lab-PK â), F1' (Lambda-Sel ââ ×â Lab-PK â), BC1 (F1 ââ ×â Lambda-Sel â), and BC2 (F1 ââ ×â Lab-PK â) showed high resistance ratios of 545.64-, 396.52-, 181.18-, and 146.54-fold, respectively compared to Lab-PK. The degree of dominance values for lambda-cyhalothrin in F1 and F1' indicates incompletely dominant resistance. The difference between observed and expected mortality in backcross populations (BC1 and BC2) revealed a polygenic resistance. In conclusion, the resistance to lambda-cyhalothrin was autosomal, incompletely dominant, and polygenic. These findings provide new insights for insect resistance management strategies to mitigate the occurrence of resistance in this global pest.
Subject(s)
Insecticide Resistance , Insecticides , Nitriles , Pyrethrins , Spodoptera , Animals , Pyrethrins/pharmacology , Nitriles/pharmacology , Insecticide Resistance/genetics , Insecticides/pharmacology , Spodoptera/drug effects , Spodoptera/genetics , Pakistan , Female , Male , Selection, Genetic , Larva/growth & developmentABSTRACT
Insect gustatory receptors (GRs) aid in the precise identification of deterrent or stimulant compounds associated with food, mating, and egg-laying. Thus, they are promising targets for developing efficient insecticides. Here, 61 GRs in the chemosensory organs of Spodoptera litura larvae and adults were identified. Among them, SlitGR206 exhibited larval labium (LL)-specific expression characteristics. To explore the role of SlitGR206, a bacterial expression system was established to produce high-quality double-stranded RNA (dsRNA) and suppress SlitGR206 expression in LL. Subsequent behavioral assessments revealed that SlitGR206 silencing influenced larval feeding preferences and absorption. Moreover, it was found to reduce the ability of larvae to forage the five crucial host odorants. These findings demonstrate that SlitGR206 likely plays an indirect regulatory role in host recognition, consequently affecting foraging behavior. This provides a crucial foundation for the analysis of functional diversity among insect GRs and the precise development of nucleic acid pesticides in the future.
Subject(s)
Feeding Behavior , Insect Proteins , Larva , Spodoptera , Animals , Spodoptera/metabolism , Spodoptera/physiology , Spodoptera/genetics , Spodoptera/growth & development , Larva/metabolism , Larva/growth & development , Larva/physiology , Insect Proteins/metabolism , Insect Proteins/genetics , Receptors, Cell Surface/metabolism , Receptors, Cell Surface/geneticsABSTRACT
Invasive insect pests, currently, pose a serious economic threat to several staple crops all over the world, one such being the fall armyworm, Spodoptera frugiperda. It was first observed in Africa since 2016, outside of its natural habitat in the Americas. Subsequently, it invaded several countries in South and South East Asia and also very recently in Australia. In all the newly invaded regions, maize is the principal crop attacked causing a serious economic concern to the poor farmers, particularly in the developing countries. Owing to the innate genetic ability, it defies many of the management options that include insecticides, Bt transgenics, and so forth. This is due to its high mobility, polyphagy and ability for quick development of resistance to several classes of insecticides. At this critical juncture, CRISPR/Cas9 mediated genome editing has shown a lot of promise in developing a novel area-wide pest management strategy called precision-guided sterile insect technique (pgSIT). pgSIT was initially demonstrated in Drosophila melanogaster which holds a greater promise for the environmentally friendly management of several globally significant agricultural pests such as S. frugiperda. Therefore, before developing both sgRNA and Cas9 transgenic lines, we have validated the target gene such as tssk2 through a non-transgenic approach by microinjecting ribo nucleo protein complex (Cas9 protein and tssk2 sgRNA) into G0 eggs of S. frugiperda. In the current investigation, we have obtained five edited males with distinct mutations which were further used for crossing studies to ascertain the effect of tssk2 editing affecting egg hatchability.
Subject(s)
CRISPR-Cas Systems , Spodoptera , Animals , Spodoptera/genetics , Male , Pest Control, Biological/methods , Gene Editing/methods , Spermatogenesis/genetics , Insect Proteins/genetics , Insect Proteins/metabolism , Female , Insect Control/methodsABSTRACT
In the Americas, transgenic crops producing insecticidal proteins from Bacillus thuringiensis Berliner (Bt, Bacillales: Bacillaceae) have been used widely to manage fall armyworm (FAW, Spodoptera frugiperda [J.E. Smith]). As resistance to Cry1 single-gene Bt maize (Zea mays L.) rapidly evolved in some FAW populations, pyramided Bt maize hybrids producing Cry1, Cry2, or Vip3Aa proteins were introduced in the 2010s. We examined field-evolved resistance to single- and dual-protein Bt maize hybrids in 2 locations in southeastern Brazil, where plant damage by FAW larvae far exceeded the economic threshold in 2017. We collected late-instar larvae in Cry1A.105â +â Cry2Ab and Cry1F maize fields and established 2 FAW populations in the laboratory. The F1 offspring reared on the foliage of Bt and non-Bt maize plants (Cry1A.105â +â Cry2Ab and Cry1F) showed neonate-to-adult survival rates as high as 70% for both populations. There was no significant difference in the life-table parameters of armyworms reared on non-Bt and Bt maize foliage, indicating complete resistance to Cry1A.105â +â Cry2Ab maize. Larval survival rates of reciprocal crosses of a susceptible laboratory strain and the field-collected populations indicated nonrecessive resistance to Cry1F and a recessive resistance to Cry1A.105â +â Cry2Ab maize. When relaxing the selection pressure, the armyworm fitness varied on Cry1A.105â +â Cry2Ab and non-Bt maize; the resistance was somewhat stable across 12 generations, without strong fitness costs, although one of the lines died confounded by a depleted-quality, artificial rearing diet. To our knowledge, this is the first report documenting the practical resistance of FAW to a pyramided Bt crop. We discuss the implications for resistance management.
Subject(s)
Bacillus thuringiensis Toxins , Bacterial Proteins , Endotoxins , Hemolysin Proteins , Insecticide Resistance , Larva , Plants, Genetically Modified , Spodoptera , Zea mays , Animals , Zea mays/genetics , Endotoxins/pharmacology , Hemolysin Proteins/pharmacology , Insecticide Resistance/genetics , Brazil , Larva/growth & development , Spodoptera/growth & development , Spodoptera/drug effects , Spodoptera/genetics , Female , Moths/growth & development , Moths/genetics , Moths/drug effects , Insecticides/pharmacology , MaleABSTRACT
Nanotechnology-based RNA interference (RNAi) offers a promising approach to pest control. However, current methods for producing RNAi nanopesticides are mainly implemented in a batch-to-batch manner, lacking consistent quality control. Herein, we present a microfluidic-based nanoplatform for RNA nanopesticide preparation using lipid nanoparticles (LNPs) as nanocarriers, taking advantage of the enhanced mass transfer and continuous processing capabilities of microfluidic technology. The dsRNA@LNPs were rapidly formed within seconds, which showed uniform size distribution, improved leaf wettability, and excellent dispersion properties. The delivery efficiency of dsRNA@LNPs was evaluated by targeting the chitin synthetase B (CHSB) gene ofSpodoptera exigua. The dsRNA@LNPs can effectively resist nuclease-rich midgut fluid degradation. Importantly, dsCHSB@LNPs exhibited increased mortality rates, significant reduction of larvae growth, and enhanced gene suppression efficiency. Therefore, a continuous nanoplatform for RNAi nanopesticide preparation is demonstrated by utilizing microfluidic technology, representing a new route to produce RNAi nanopesticides with enhanced quality control and might accelerate their practical applications.