Search Results (77)

Insects represent powerful experimental systems for investigating host–microorganism interactions, providing valuable insights into bacterial pathogenicity, immune regulation, symbiosis, and antimicrobial discovery. This review examines the complex relationships between insects and bacteria, focusing on the mechanisms that control infection, immune activation, and microbial adaptation. Particular attention is given to the routes of pathogen entry and to the conserved innate immune pathways that coordinate host defenses, including the Toll, Imd, Duox, and Jak/Stat signaling cascades. The review illustrates how bacterial pathogens exploit toxins, immune evasion strategies, and metabolic adaptation to overcome host defenses, while insects rely on tightly regulated cellular and humoral responses, antimicrobial peptides, melanization, and microbiota-mediated homeostasis. Interactions between pathogenic and commensal bacteria in the insect gut are discussed in the context of immune tolerance, dysbiosis, and ecological adaptation. The dual role of bacterial virulence factors in both pathogenesis and symbiosis is highlighted through examples involving entomopathogenic bacteria such as Photorhabdus spp., Xenorhabdus spp., and Bacillus thuringiensis. In addition, the review summarizes the use of insect models, including Drosophila melanogaster, Galleria mellonella, Bombyx mori, and Apis mellifera, in experimental infections aimed at studying virulence mechanisms, host immune responses, and antimicrobial efficacy. Finally, multi-omic approaches, including transcriptomics, metabolomics, epigenomics, and single-cell technologies are discussed as transformative tools for dissecting host–microbe interactions at molecular and systems levels. Overall, insect–bacteria interactions emerge as dynamic and evolutionarily shaped systems in which immunity, metabolism, microbiota composition, and environmental factors are closely interconnected, offering important perspectives for both basic research and the development of sustainable biocontrol and antimicrobial strategies. Full article

Background/Objectives: Antibiotics are routinely used in crustacean larviculture to mitigate bacterial infections, yet their widespread application compromises larval ontogeny. Probiotics and microalgae offer sustainable alternatives, but their combined molecular effects in crustacean larvae remain poorly characterized. This study aimed to evaluate the physiological and transcriptomic impacts of a probiotics–microalgae consortium versus antibiotics in mud crab (Scylla paramamosain) zoea, with the goal of elucidating mechanisms underlying improved larval development and identifying potential antibiotic alternatives. Methods: Scylla paramamosain larvae were reared under five treatments: clear water control (CN), microalgae alone (MA), probiotics alone (PB), a probiotics–microalgae consortium (PB-MA), and the antibiotic (AB) florfenicol. Samples were collected at 6 h and 24 h post-treatment during the first (Z1) and third (Z3) zoeal stages. Growth performance was assessed via survival and larval stage index, and multi-time point transcriptomic sequencing was performed to analyze dynamic gene expression profiles. Results: The PB-MA consortium significantly enhanced stage-specific survival from Z3 to Z5 and accelerated developmental progression compared to control and antibiotic groups. Transcriptomic analysis revealed from 492 to 2854 differentially expressed genes across treatments. PB-MA treatment was associated with the sustained upregulation of immune-related pathways (lysosome and Toll/Imd signaling), oxidative stress responses (peroxisome and glutathione metabolism), and energy metabolism (TCA cycle and carbon metabolism), whereas antibiotics predominantly suppressed these pathways. Key candidate genes, including NPC1, NAGA, ACOX1, HAO1, MUT, and PK, were prominently induced in PB-MA-treated larvae. Conclusions: The probiotics–microalgae consortium enhances basal immunity, antioxidant capacity, and metabolic adaptability in mud crab larvae at the molecular level. These findings provide transcriptomic evidence supporting the replacement of antibiotics with synergistic microbial consortia in sustainable crustacean larviculture. Full article

Pathogen manipulation of host behavior is a widespread evolutionary strategy to enhance its transmission, yet whether different pathogens elicit distinct behavioral and molecular responses in the same host remains poorly understood. We performed parallel behavioral assays and comparative transcriptomic analyses on third-instar Lymantria dispar larvae infected with Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV, virus), Staphylococcus aureus (bacterium) and Metarhizium anisopliae (fungus). Climbing height was recorded over 72 h post-infection, and gene expression pattern was profiled using RNA-seq at 72 h. Only LdMNPV infection induced significant, sustained upward climbing behavior among the three pathogen infection groups. All three pathogens activated Toll and IMD immune pathways, but LdMNPV triggered substantially broader transcriptomic reprogramming. Notably, the virus specifically upregulated multiple energy metabolism pathways (nicotinate/nicotinamide metabolism, pyruvate metabolism, TCA cycle and oxidative phosphorylation) and the neuroactive ligand-receptor interaction pathway—a pattern absent in bacterial and fungal infections. LdMNPV drove tree-top disease through a virus-specific, multi-system manipulation strategy that couples metabolic activation with neural signaling modulation. This comparative study reveals fundamental differences in behavioral manipulation across pathogen kingdoms and provides candidate pathways for functional validation. Full article

The single von Willebrand factor C (SVWC) domain-containing protein family represents a crucial class of immune molecules recently identified in insects and crustaceans. Initially regarded as functional analogs of vertebrate interferons (IFNs) due to their virus-induced expression and activation of the Janus kinase-signal transducer and activator of the transcription (JAK-STAT) pathway, recent studies have revealed that SVWC proteins possess far more complex functions. Many SVWC members are themselves a novel class of pattern recognition receptors (PRRs) that can directly bind to viruses and bacteria. Importantly, SVWCs are not a single entity but a highly diverse family—multiple subtypes exist in Drosophila, Bombyx mori, and shrimp—a gene expansion that implies functional differentiation. This review systematically examines the multifunctionality of SVWC proteins in insects and crustaceans, with a particular focus on the functional specialization driven by subtype diversity. We delve into the complex regulatory networks governing SVWC expression, including the differential activation by nuclear factor kappa B (NF-κB) pathways (Dorsal, Rel-2, Relish) and interferon regulatory factor (IRF) pathways. We detail the unique signaling mechanism by which SVWCs activate the JAK-STAT pathway via integrins, rather than the canonical Domeless receptor. Furthermore, we extend the discussion to the emerging roles of SVWCs as PRRs in humoral immunity (activating Toll/IMD pathways to induce antimicrobial peptides) and cellular immunity (mediating hemocyte phagocytosis). Based on current evidence, We propose that diverse SVWC subtypes may recognize distinct pathogens, bind to different integrin receptors, and activate specific STAT variants via disparate upstream induction pathways, thereby establishing a systematic and hierarchical immunoregulatory network. This understanding positions the SVWC protein family as a central hub in the insect immune network and offers a novel perspective on the complexity and evolution of invertebrate immunity. Full article

This study conducted a 70-day feeding trial to evaluate the effects of dietary Lactobacillus plantarum supplementation (0, 0.1, 1.0, and 10.0 g/kg) in red claw crayfish (Cherax quadricarinatus). Growth performance, hepatopancreatic antioxidant-related parameters, and the expression of genes related to the Toll/Imd and JAK-STAT pathways were determined. Results showed that dietary L. plantarum supplementation significantly improved weight gain rate, specific growth rate, daily growth index, and feed efficiency, which were increased by 23.57%, 5.10%, 9.67%, and 7.90%, respectively, and reduced mortality rate by 60.00% compared with the control group (p < 0.05), enhanced the activities of glutathione peroxidase, catalase, superoxide dismutase and total antioxidant capacity, and reduced malondialdehyde levels in the hepatopancreas (p < 0.05). Furthermore, dietary L. plantarum supplementation was associated with the upregulated expression of key genes related to the Toll/Imd and JAK-STAT signaling pathways (p < 0.05). The expression levels of tumor necrosis factor-α, interleukin-1β, and transforming growth factor-β1 were also significantly increased (p < 0.05). Overall, these findings suggest that dietary L. plantarum supplementation improved growth performance and antioxidant-related and immune-related parameters in red claw crayfish, and that these effects were associated with the upregulated expression of genes involved in the Toll/Imd and JAK-STAT pathways. Among the tested treatments, 1.0 g/kg L. plantarum produced the most favorable overall response. Full article

The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), poses a significant threat to global tomato production. However, environmentally sustainable management strategies for this pest, as well as its mechanisms of insecticide resistance, remain insufficiently understood. Broflanilide, a novel meta-diamide compound, can bind specifically to the transmembrane domain of the RDL subunit, causing prolonged opening of the chloride channel, disruption of neurotransmission, and ultimately insect paralysis and death. This study employed the leaf immersion method to conduct bioassays on the second-instar larvae of T. absoluta to evaluate physiological responses to sublethal concentrations of the novel amide insecticide broflanilide. Subsequently, high-throughput transcriptome sequencing was performed to investigate changes in gene expression and metabolic pathways. Bioassay results determined the larval sublethal concentrations of broflanilide to be 0.136 mg/L (LC₁₀) and 0.210 mg/L (LC₃₀). Sublethal exposure significantly prolonged the larval period, reduced pupal weight, and inhibited fecundity of female adults. Transcriptomic and qPCR analyses revealed that, compared with the control (CK), expression of the vitellogenin gene Vg decreased by 15.99% and 30.27% under LC₁₀ and LC₃₀ treatments, respectively, while its receptor gene VgR decreased by 11.56% and 24.49%. Similarly, expression of chitin synthase genes chs1 and chs2 declined by 13.56% and 30.17% (chs1), and 7.85% and 19.45% (chs2), respectively. Gene expression analysis elucidated how sublethal insecticides treatment impact larval development and fecundity. Furthermore, the study revealed upregulation of cytochrome P450-mediated detoxification pathways and Toll/Imd immune signaling pathways under broflanilide stress, indicating activation of a coordinated defense response in T. absoluta. Sublethal broflanilide exposure modulated larval gene expression to balance growth, development, and stress adaptation. Such exposure exerts selective pressure on susceptible populations, potentially driving adaptive shifts in detoxification metabolism and contributing to the development of field resistance. These findings advance our understanding of the sublethal effects of novel insecticides and provide valuable insights for insecticide deployment strategies and resistance management. Full article

Bt Cry toxins remain the cornerstone of transgenic crop protection against Lepidopteran pests, yet field-evolved resistance, particularly in invasive species such as Spodoptera frugiperda and Helicoverpa armigera, can threaten their long-term efficacy. This review presents a comprehensive and unified mechanistic framework that synthesizes current understanding of Bt Cry toxin modes of action and the complex, multilayered regulatory mechanisms of field-evolved resistance. Beyond the classical pore-formation model, emerging evidence highlights signal transduction cascades, immune evasion via suppression of Toll/IMD pathways, and tripartite toxin–host–microbiota interactions that can dynamically modulate protoxin activation and receptor accessibility. Resistance arises from target-site alterations (e.g., ABCC2/ABCC3, Cadherin mutations), altered midgut protease profiles, enhanced immune regeneration, and microbiota-mediated detoxification, orchestrated by transcription factor networks (GATA, FoxA, FTZ-F1), constitutive MAPK hyperactivation (especially MAP4K4-driven cascades), along with preliminary emerging findings on non-coding RNA involvement. Countermeasures now integrate synergistic Cry/Vip pyramiding, CRISPR/Cas9-validated receptor knockouts revealing functional redundancy, Domain III chimerization (e.g., Cry1A.105), phage-assisted continuous evolution (PACE), and the emerging application of AlphaFold3 for structure-guided rational redesign of resistance-breaking variants. Future sustainability hinges on system-level integration of single-cell transcriptomics, midgut-specific CRISPR screens, microbiome engineering, and AI-accelerated protein design to preempt resistance trajectories and secure Bt biotechnology within integrated resistance and pest management frameworks. Full article

Hemocytes (insect blood cells) consist of several morphological types and perform a variety of physiological processes, including immune responses. However, we do not know how many cell types are functionally differentiated in hemocytes or how they perform independent physiological processes. To address this fundamental question, we analyzed hemocyte transcripts with a single-cell RNA-sequencing (scRNA-Seq) technique. The hemocytes were collected from larvae of a lepidopteran insect, Spodoptera exigua, in which four different hemocyte types were morphologically recognized. scRNA-Seq discriminated 24 hemocyte clusters based on the transcripts of each cell. The clusters were separated into seven functional groups predicted from the top three highly expressed and annotated genes in each cluster: active protein synthesis (12 clusters), apoptosis (5 clusters), melanization (2 clusters), modulating cell shape (6 clusters), antimicrobial peptide production (9 clusters), calcium homeostasis (8 clusters), and cell repairing (1 cluster). Signal components of Toll/IMD immune pathways were variably expressed among the clusters. Biosynthetic genes associated with oxylipin immune mediators were specifically expressed among the clusters. Immune effectors such as melanization and apoptosis were expressed in specific hemocyte clusters. Specifically expressed genes that discriminate hemocyte types were used to develop fluorescence in situ hybridization (FISH) markers. In addition, five new hemocyte groups, which were not among the four known hemocyte types in the transcript profile, were identified and discriminated with their specific FISH markers. The hemocyte clusters underwent dynamic changes upon immune challenge. A trajectory analysis using the transcriptome suggests at least three different hemocyte differentiation pathways. These results indicate that the hemocytes of S. exigua are functionally highly differentiated and exhibit a dynamic transition in response to environmental changes. Full article

The domesticated silkworm, Bombyx mori, is a highly valued biodiversity and economic asset, acclaimed for its silk production, besides making important contributions to various scientific disciplines. However, the sericulture industry faces ongoing threats from bacterial and viral infections, which severely impact silkworm health and silk yield. This review provides a comprehensive overview of the innate immune response of B. mori against bacterial and viral pathogens, emphasizing the fundamental molecular and cellular defense mechanisms. We explore the humoral and cellular immune response using antimicrobial peptides (AMPs), pattern recognition receptors (PRRs) like peptidoglycan recognition protein (PGRP), and glucan recognition protein (GRP), which activate canonical signaling pathways. The review further highlights the molecular mechanisms underlying the silkworm’s defense against viruses, incorporating RNA interference (RNAi), apoptosis, and distinct signaling pathways such as Toll and Imd, JAK/STAT, and STING. We also discussed the viral suppression strategies and modulation of host metabolism during infection. Furthermore, the review explores the recent use of CRISPR-Cas gene editing to enhance disease resistance, presenting a promising avenue for mitigating pathogen-induced losses in sericulture. By elucidating these mechanisms, the work provides a synthesis that is critical in terms of developing particular interventions and developing more resistant silkworm strains to ensure that the industry of sericulture becomes viable and productive. Full article

The gut microbiota of Drosophila melanogaster offers a simplified yet powerful system to study conserved mechanisms of host–microbe interactions. Unlike the highly complex mammalian gut microbiota, which includes hundreds of species, the fly gut harbors a small and defined community dominated by Lactobacillus and Acetobacter. Despite its low diversity, this microbiota exerts profound effects on host physiology. Commensal bacteria modulate nutrient acquisition, regulate insulin/TOR signaling, and buffer dietary imbalances to support metabolic homeostasis and growth. They also influence neural and behavioral traits, including feeding preferences, mating, and aggression, through microbial metabolites and interactions with host signaling pathways. At the immune level, microbial molecules such as peptidoglycan, acetate, uracil, and cyclic dinucleotides activate conserved pathways including Imd, Toll, DUOX, and STING, balancing antimicrobial defense with tolerance to commensals. Dysbiosis disrupts this equilibrium, accelerating aging, impairing tissue repair, and contributing to tumorigenesis. Research in Drosophila demonstrates how a low-diversity microbiota can shape systemic host biology, offering mechanistic insights relevant to human health and disease. Full article

Dioryctria abietella (Lepidoptera: Pyralidae) is a destructive forest pest for coniferous trees. Bacillus thuringiensis has been widely applied in forestry as a biological control agent to control it. However, the mechanisms of Bt-induced mortality in D. abietella, particularly its effects on gene expression and enzyme activities, remain unclear. Here, bioassay, enzyme assay, transcriptome sequencing, and gene expression profiling were employed to explore the relationship between the toxin-receptor, defense, and lethal mechanisms of D. abietella after Bt exposure. In a toxicity bioassay, Bacillus thuringiensis galleriae 05041 strain (Bt05041) was the most toxic insecticide to the larvae of D. abietella, with LC₅₀ values of 3.15 × 10⁸ Colony-Forming Units (CFUs) mL⁻¹ at 72 h after treatment. Transcriptome analysis revealed that the gene expression patterns of D. abietella after 8 h of Bt05041 exposure (Bt8) varied considerably from the Bt05041-treated for 2 h group (Bt2). In the Bt2 group, differentially expressed genes were significantly enriched in cellular and bioenergy pathways of lysosome, insulin signaling, cGMP-PKG signaling, etc. Immune-related pathways were activated, namely cAMP, AMPK, MAPK, Rap1, IMD, and Toll pathways. Meanwhile, Bt8 treatment caused metabolic changes in basic substances such as amino acids, glucose, nucleic acids, and fatty acids. Bt05041 exposure activated the activities of defense enzymes and induced gene expression changes in D. abietella larvae. Among them, most Bt-receptor genes had higher expression levels than defense enzyme genes. Overall, these findings reveal a possible mechanism underlying Bt-mediated death in D. abietella larvae. This work provides valuable information in terms of biological control strategies. Full article

Penaeus vannamei aquaculture production accounts for the majority of total shrimp aquaculture output, but it has suffered a severe decline in production and economic losses due to WSSV disease. Therefore, elucidating the relationship between the host immune system and pathogens is crucial for shrimp disease prevention and control. Integrins, as receptor-related molecules, have been shown to participate in various physiological functions, including cell migration, organismal development, and the pathogenesis of multiple diseases. However, the regulatory mechanisms of integrin genes in the shrimp immune system remain unclear. This study reports that integrins may regulate the Toll, IMD, and STAT signaling pathways in P. vannamei by influencing Spätzle, TLR, and Domeless, thereby affecting the shrimp’s innate immune system against diseases. Additionally, integrins can inhibit viral entry and replication. Through RNA interference (RNAi) experiments, it was found that knocking down Pv-Integrin β increases the viral load of white spot syndrome virus (WSSV), making shrimp more susceptible to WSSV and giving rise to increasing mortality. Further research indicates that Pv-Integrin β acts as an upstream recognition receptor in the disease resistance immune pathway, influencing other signaling pathway receptors to regulate the innate immune system. Importantly, knocking down Pv-Integrin β upregulates the expression of antimicrobial peptides such as ALF1 and ALF2, but reduces the expression of Crustin1, Crustin2 and prophenoloxidase. In conclusion, this study reveals that Pv-Integrin β regulates the disease resistance immune signaling pathways by affecting the related receptors. Full article

Tachypleus tridentatus is a rare and endangered marine organism with considerable scientific and economic value. It has existed on Earth for about 450 million years and its continuation to the present day may be related to its unique immune system. Owing to its drastic population decline, diverse technical approaches are required for its recovery, and the development and growth of its larvae are crucial in this context. Vibrio parahaemolyticus is a common marine pathogen that impairs the healthy growth of marine organisms. The peak period of V. parahaemolyticus occurrence is from May to November, which significantly overlaps with the T. tridentatus spawning period from April to September. However, the response mechanisms of juvenile T. tridentatus to V. parahaemolyticus stress remain unknown. Hence, in this study, we aimed to investigate these response mechanisms through acute toxicity assays, histological observations, and transcriptome analysis. The results showed that the 48 h LD₅₀ of V. parahaemolyticus-infected T. tridentatus larvae was determined to be 1.31 × 10⁸ CFU/g. Histological analysis showed that V. parahaemolyticus damaged the larval tissue. In addition, RNA sequencing (RNA-Seq) identified 2347 differentially expressed genes (DEGs; 1440 upregulated and 907 downregulated genes) and 243 enriched signaling pathways. Functional enrichment analysis revealed the enrichment of immunoregulatory pathways, including the Wnt signaling pathway, ECM-receptor interaction, aminoacyl-tRNA biosynthesis, and Toll and Imd signaling pathways. Seventeen DEGs were randomly selected for real-time RT-PCR (RT-qPCR) validation, and their expression patterns were consistent with those obtained via RNA-Seq. The study of the response mechanism of T. tridentatus larvae to V. parahaemolyticus stress provides scientific references for the protection of T. tridentatus habitats and the recovery of its population size. Full article

Extreme weather events such as heavy rainfall significantly reduce surface salinity in coastal waters, presenting considerable challenges to the aquaculture of Japanese scallops (Mizuhopecten yessoensis) in shallow cage systems. This study investigated the effects of chronic low-salinity stress on the growth performance, antioxidant capacity, and gene expression profile of M. yessoensis using a 60-day salinity gradient experiment. S33 represents the control treatment with normal seawater salinity (33‰), while S30, S28, and S26 represent experimental groups with progressively lower salinities of 30‰, 28‰, and 26‰, respectively. A decline in salinity was accompanied by an increase in oxygen consumption. The S26 group exhibited a higher ammonia excretion rate (2.73 μg/g·h) than other groups, indicating intensified nitrogen metabolism. Growth was inhibited under low-salinity conditions. The S33 group exhibited greater weight gain (16.7%) and shell growth (8.4%) compared to the S26 group (11.6% and 6%), which also showed a substantially higher mortality rate (46%) compared to the control (13%). At 28‰, antioxidant enzyme activities (T-AOC, SOD, CAT, POD) were elevated, indicating a moderate level of stress. However, at the lowest salinity (26‰), these indicators decreased, reflecting the exhaustion of the antioxidant systems and indicating that the mollusks’ adaptive capacity had been exceeded, leading to a state of stress fatigue. NAD-MDH activity was elevated in the S26 group, reflecting enhanced aerobic metabolism under stress. Transcriptome analysis revealed 564 differentially expressed genes (DEGs) between the S33 and S26 groups. Functional enrichment analysis indicated that these DEGs were mainly associated with immune and stress response pathways, including NF-κB, TNF, apoptosis, and Toll/Imd signaling. These genes are involved in key metabolic processes, such as alanine, aspartate, and glutamate metabolism. Genes such as GADD45, ATF4, TRAF3, and XBP1 were upregulated, contributing to stress repair and antioxidant responses. Conversely, the expressions of CASP3, IKBKA, BIRC2/3, and LBP were downregulated, potentially mitigating apoptosis and inflammatory responses. These findings suggest that M. yessoensis adapts to chronic low-salinity stress through the activation of antioxidant systems, modulation of immune responses, and suppression of excessive apoptosis. This study provides new insights into the molecular mechanisms underlying salinity adaptation in bivalves and offers valuable references for scallop aquaculture and selective breeding programs. Full article

Melanin is an important component of the body color of honeybees, and its formation changes with the age of a capped brood of bees. However, up to now, the regulatory mechanism of melanin formation in honeybees remains unclear. To analyze the differential expression profile of microRNAs (miRNAs) in worker bees of Apis mellifera and to reveal the regulatory roles of differentially expressed miRNAs (DEmiRNAs) and mRNAs in the formation process of melanin during the capped brood stage, we used sRNA-seq technology and related software to analyze samples from four key developmental stages during the capped brood stage, when body color develops in Apis mellifera, namely, mature larvae (L0), pre-pupae (PP3), early pupae (P6) and mid-pupae (P9). A total of 1291 miRNAs were identified by bioinformatics. Three comparison groups were analyzed: L0 vs. PP3, PP3 vs. P6, and P6 vs. P9. A total of 171, 94, and 19 DEmiRNAs were identified in these groups, respectively, which regulate 1481, 690, and 182 differentially expressed target mRNAs (target DEmRNAs). The functional analysis of target DEmRNAs indicated that DEmiRNAs might regulate the formation of capped brood melanin in honeybees by activating expression changes in key genes in signaling pathways, such as the Wnt signaling pathway, melanogenesis, and the Toll and Imd signaling pathway, through activating miR-315-x, miR-8, ple, yellow family genes, wnt1, etc. Our research provides a theoretical basis for future analysis of the regulatory role of miRNAs in the formation of melanin in honeybees. Full article