Search Results (53)

To elucidate the role of the peptidoglycan recognition protein OfPGRP-B in the innate immunity of Ostrinia furnacalis, a recombinant expression system was established using a prokaryotic expression strategy. The recombinant plasmid encoding OfPGRP-B was constructed and expressed in Escherichia coli, and the target protein was successfully obtained after induction. Purification and Western blot analysis confirmed that the molecular weight of the recombinant protein was consistent with the predicted value. The immune functions of OfPGRP-B were further investigated through antibacterial activity assays, bacterial agglutination tests, amidase activity assays, phenoloxidase (PO) cascade activation, and in vivo melanization assays. The results showed that OfPGRP-B alone exhibited weak direct antibacterial activity against the tested bacteria but significantly promoted bacterial agglutination and was capable of degrading peptidoglycan derived from E. coli and Staphylococcus aureus. In the presence of bacterial peptidoglycan, OfPGRP-B enhanced the activation of the PO cascade, but had no significant effect on in vivo melanization. These findings suggest that OfPGRP-B may function as an immunomodulatory factor involved in the humoral immune response of O. furnacalis, providing a theoretical basis for the development of biological control strategies based on host immune mechanisms. Full article

Peptidoglycan recognition proteins (PGRPs) are conserved pattern recognition receptors (PRRs) that play key roles in insect innate immunity by binding bacterial peptidoglycan (PGN) and activating downstream signaling pathways. The Dendrolimus kikuchii, a major defoliator of coniferous forests in southern China, has incompletely characterized immune defenses. This study systematically identified the PGRP gene family in D. kikuchii based on genome-wide data, identifying 10 PGRP genes with typical PGRP/Amidase_2 conserved domains, including 6 PGRP-S proteins and 4 PGRP-L proteins. Additionally, to further investigate the evolutionary relationships of these PGRP genes, a maximum likelihood (ML) phylogenetic tree was constructed using PGRP amino acid sequences from 6 different insect species, along with the 10 PGRP amino acid sequences from D. kikuchii. Phylogenetic analysis revealed that the DkikPGRP genes of D. kikuchii are distributed across distinct evolutionary branches and share high homology with PGRP genes from other insects, suggesting a close evolutionary relationship between the PGRP genes of D. kikuchii and those of other insect species. Transcriptome profiling revealed that DkikPGRP-S1, -S2, -S3, -S4, and -S5 were upregulated in the midgut, fat body, and hemolymph after Bt infection, showing tissue- and time-specific immune responses. Functional assays using siRNA knockdown demonstrated distinct roles of DkikPGRP-S4 and DkikPGRP-S5: DkikPGRP-S5 mainly promoted antimicrobial peptide (AMP) expression, including attacin, lebocin, lysozyme, and cecropin, whereas DkikPGRP-S4 showed a complex regulatory pattern, enhancing lebocin and lysozyme but suppressing attacin without affecting gloverin or cecropin. Silencing either gene significantly increased larval mortality upon Bt challenge. These results highlight the specialized immune regulatory functions of PGRPs in D. kikuchii, provide new insights into host–pathogen interactions, and suggest potential molecular targets for sustainable pest management strategies. 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 American cockroach (Periplaneta americana) serves as an exemplary model for regeneration research due to its exceptional regenerative capabilities, particularly in appendage regeneration. In this study, regenerated coxa tissue underwent histological analysis through H & E straining. Microscopic examination revealed the progression of regeneration. To elucidate the underlying mechanisms, a comparative transcriptomic analysis was conducted between regenerating legs and non-amputated control legs. This analysis identified 2343 differentially expressed genes (DEGs) between 0 days post-amputation (0 dpa) and 7 dpa, 2963 DEGs between 14 dpa and 0 dpa, and 3135 DEGs between 14 dpa and 7 dpa. Significantly, several DEGs are associated with growth- or regeneration-related processes, including extracellular matrix (different collagen, Pro-resilin isoforms, integrin beta (itgb) and matrix metalloproteinase (mmp)), immune-related genes (Toll-like receptor 13 (tlr13), defensin (def), drosomycin-like defensin (dld), Polyphenoloxidases2 (ppo2), cytochrome P450 (p450), peptidoglycan recognition protein (pgrp) and secreted C-type lectin (sClec)), insulin-like growth factor (IGF) and Epidermal Growth Factor Receptor (EGFR). Functional validation through RNA interference (RNAi) further suggested that EGFR and a specific C-type lectin (Regenectin) regulate leg regeneration in Periplaneta americana. These findings enhance our understanding of the molecular mechanisms governing regeneration in this species. Full article

Endolysins, phage-derived enzymes capable of lysing bacterial cell walls, hold significant promise as novel antimicrobials against resistant Gram-positive and Gram-negative pathogens. In this study, we undertook an integrative approach combining extensive in silico analyses and experimental validation to characterize the novel endolysin LysPALS22. Initially, sixteen endolysin sequences were selected based on documented lytic activity and enzymatic diversity, and subjected to multiple sequence alignment and phylogenetic analysis, which revealed highly conserved catalytic and binding domains, particularly localized to the N-terminal region, underscoring their functional importance. Building upon these sequence insights, we generated three-dimensional structural models using Swiss-Model, EBI-EMBL, and AlphaFold Colab, where comparative evaluation via Ramachandran plots and ERRAT scores identified the Swiss-Model prediction as the highest quality structure, featuring over 90% residues in favored conformations and superior atomic interaction profiles. Leveraging this validated model, molecular docking studies were conducted in PyRx with AutoDock Vina, performing blind docking of key peptidoglycan-derived ligands such as N-Acetylmuramic Acid-L-Alanine, which exhibited the strongest binding affinity (−7.3 kcal/mol), with stable hydrogen bonding to catalytic residues ASP46 and TYR61, indicating precise substrate recognition. Visualization of docking poses using Discovery Studio further confirmed critical hydrophobic and polar interactions stabilizing ligand binding. Subsequent molecular dynamics simulations validated the stability of the LysPALS22–NAM-LA complex, showing minimal structural fluctuations, persistent hydrogen bonding, and favorable interaction energies throughout the 100 ns trajectory. Parallel to computational analyses, LysPALS22 was heterologously expressed in Escherichia coli (E. coli) and Pichia pastoris (P. pastoris), where SDS-PAGE and bicinchoninic acid assays validated successful protein production; notably, the P. pastoris-expressed enzyme displayed an increased molecular weight (~45 kDa) consistent with glycosylation, and achieved higher volumetric yields (1.56 ± 0.31 mg/mL) compared to E. coli (1.31 ± 0.16 mg/mL), reflecting advantages of yeast expression for large-scale production. Collectively, these findings provide a robust structural and functional foundation for LysPALS22, highlighting its conserved enzymatic features, specific ligand interactions, and successful recombinant expression, thereby setting the stage for future in vivo antimicrobial efficacy studies and rational engineering efforts aimed at combating multidrug-resistant Gram-negative infections. Full article

Due to their evolutionary divergence from mammals, zebrafish (Zf, Danio rerio), which are frequently employed in biomedical research, provide a distinctive viewpoint on innate immune systems. The Toll-like receptor 4/myeloid differentiation factor 2/cluster of differentiation 14 (TLR4/MD-2/CD14) complex in mammals detects lipopolysaccharide (LPS), a crucial component of Gram-negative bacteria, and it causes potent inflammatory reactions through a Toll/interleukin-1 receptor domain-containing adapter-inducing interferon-β (TRIF)-dependent and myeloid differentiation primary response 88 (MyD88)-dependent pathways. However, key components of this system, such as a responsive TLR4 axis and a functional CD14 ortholog, are absent in Zf. The Zf species nevertheless reacts to LPS, which leads to research into other recognition systems. This review looks at a number of TLR4-independent processes in Zf, such as scavenger receptors (SRs) including scavenger receptor class B type 1 (SR-BI) and cluster of differentiation 36 (CD36), nucleotide-binding oligomerization domain-containing protein 1 (NOD1)-dependent cytosolic sensing, peptidoglycan recognition proteins (PGRPs), Complement Component 3 (C3), and caspase-1-like protein 2 (Caspy2)-mediated inflammasome activation. An alternative and flexible immune system that makes up for the lack of canonical TLR4 signaling is revealed by these mechanisms. Additionally, the discovery of lymphocyte antigen 96 (ly96), an ortholog of MD-2 found in Zf, suggests evolutionary similarity; however, as it is only functional in artificial systems, it demonstrates minimal overlap with mammalian MD-2 activity. Knowing these pathways provides important information for studying inflammation, infection, and immunological modulation in vertebrates using Zf as a model. It also clarifies the evolutionary flexibility of innate immune recognition. Full article

The yellow peach moth (YPM), Conogethes punctiferalis, is an important agricultural insect pest causing severe damage to corn in eastern China. Beauveria bassiana is an effective, eco-friendly, and promising alternative agent for controlling this insect pest. However, insect immunity can limit the ability of fungal infections. In order to understand the immune response mechanism of YPM, a comparative proteomic analysis of non-infected and B. bassiana-infected larvae was conducted using the isobaric tags for relative and absolute quantification (iTRAQ) technique. On the basis of proteomic analysis, 4195 quantifiable proteins were identified from a total of 29,155 peptides. The functions of the identified proteins were annotated in four databases (GO, COG, KEGG, and IPR). A total of 132 immune-related proteins were screened, including 46 pathogen recognition proteins, 27 extracellular signal modulation proteins, and 59 immune effectors. Furthermore, 70 differentially expressed proteins (DEPs) were identified, including 57 up-regulated proteins and 13 down-regulated proteins. Among these, four DEPs were related to immunity, namely one defense protein and three peptidoglycan recognition proteins. Six randomly selected immune-related proteins associated with target genes were validated for qRT-PCR, and the results indicated that the accuracy and reliability of the proteome sequencing data were high. Taken together, the results enrich the fundamental knowledge of YPM immune responses to B. bassiana infection and provide a new insight into insect−pathogen interactions. Full article

Peptidoglycan recognition proteins (PGRPs) are essential for innate immune recognition and regulation from insects to mammals. However, the specific role of PGRPs in responding to Bacillus thuringiensis (Bt) infection and maintaining midgut microbial homeostasis in Plutella xylostella remains poorly understood. In this study, we identified and characterized a PGRP gene from P. xylostella, designated PxPGRP4. The spatiotemporal expression analysis revealed that PxPGRP4 is predominantly expressed in the midgut of naïve larvae and at adult stages. A homozygous mutant strain featuring a four-base pair nucleotide deletion was successfully generated through CRISPR/Cas9-mediated knockout of PxPGRP4. The bioassay results indicated that the susceptibility of P. xylostella larvae to Cry1Ac protoxin was significantly increased by the loss of PxPGRP4 expression. Furthermore, 16S rRNA sequencing and qPCR analysis revealed that the PxPGRP4 mutants exhibited a significantly reduced total bacterial load and altered microbiota composition in the midgut compared to the wild-type strain, with a shift in the dominant bacterial family from Enterobacteriaceae to Enterococcaceae. Additionally, the knockout of PxPGRP4 resulted in significant alterations in the expression of midgut immune-related genes. These findings highlight the crucial role of PxPGRP4 as a modulator of midgut microbiota and immune responses and provide valuable insights into Bt resistance management. Full article

The primary objective of this study was to identify and characterize pathogen defense proteins in the Nicotiana tabacum L. proteome, focusing on their structural, functional, and evolutionary properties, as well as their interactions with pathogen-derived molecules. Specifically, we aimed to comprehensively analyze the proteome to pinpoint potential uncharacterized defense-related protein that has emerging roles in immune responses and antioxidant activity across plants and animals. Through integrated computational approaches, we determined evolutionary relationships, and structural modeling of the selected protein was performed using different modeling software, followed by validation through multiple metrics, including stereochemical checks (Ramachandran plot), MolProbity analysis, and Z-scores. We further investigated the functional binding regions or interaction sites. We performed molecular docking to investigate the molecular interactions between selected proteins and pathogen-associated molecular patterns (PAMPs), specifically β-glucan and peptidoglycan (PGN), to elucidate their defensive mechanisms. Last, normal mode analysis (NMA), molecular dynamics simulation (MDS), and post-simulation analyses were employed to evaluate the stability and mobility of the protein–ligand complexes. Uncharacterized vitellogenin-like protein (VLP: ID A0A1S4CXB2) with the potential defense domain chosen because of its predicted immune-related features, stress response patterns, and unknown pathogen role at new immunity functions. Phylogenetic analysis revealed significant sequence homology with VLPs from other members of the Solanaceae family. Structural modeling showed a high-quality model, with docking studies indicating a stronger affinity for PGN (−10.16 kcal/mol) and β-glucan (−7.19 kcal/mol), highlighting its potential involvement in pathogen defense. NMA, MDS, and post-simulation analyses revealed that PGN exhibits more substantial binding stability and more extensive interactions with VLP than β-glucan. Our findings confirmed that VLPs in N. tabacum may function as pattern recognition receptors (PRRs), capable of recognizing and responding to pathogens by activating immune signaling pathways. Future experimental validation of these interactions could further elucidate the role of VLPs in plant defense and their potential application in biotechnological approaches for sustainable agriculture. Full article

Spodoptera frugiperda is a globally significant migratory agricultural pest that requires proactive monitoring. Understanding the molecular mechanisms underlying the interactions between pathogenic microorganisms and S. frugiperda is crucial for enhancing the effectiveness of microbial control agents against this pest. This study used transcriptome sequencing and molecular biology techniques on S. frugiperda larvae infected by bacteria and fungi to investigate the composition and molecular regulatory mechanisms of its immune system. A total of 598 immune-related genes were identified. Upon microbial infection, most immune-related genes showed an upregulated expression trend. Phylogenetic analysis revealed that the immune gene repertoire of S. frugiperda is relatively conserved. The expression of the genes of peptidoglycan recognition proteins in different tissues of S. frugiperda induced by microorganisms at different times was verified using qPCR, and the results confirmed that these genes were significantly upregulated under specific pathogenic infections. This study elucidates the immune transcriptome of S. frugiperda in response to various pathogenic microorganisms, providing valuable insights for improving the effectiveness of existing microbial agents and developing new, highly efficient, and specific biopesticides. Full article

Despite its ecological and economic importance, many aspects of Varroa destructor’s biology remain poorly understood, particularly its defense mechanisms against pathogens. The limited knowledge of Varroa’s immunity has hindered the development of RNA interference (RNAi)-based strategies targeting immune-related genes. In this study, we investigated the immune gene repertoire of V. destructor by querying its NCBI nr protein database and comparing it to model species of ticks (Ixodes scapularis) and mites (Galendromus occidentalis and Tetranychus urticae). Transcription of candidate immune genes was confirmed by analyzing a de novo assembled transcriptome of V. destructor. Our findings reveal that V. destructor shares key immunological traits with ticks, including lysozymes, chitinases, and thioester-containing proteins (TEPs), but also shares the absence of transmembrane peptidoglycan recognition proteins (PGRPs), Gram-negative binding proteins, and several lectin families involved in pathogen recognition. Additionally, Varroa mites, like ticks, lack homologs of crucial immune signaling components, such as the unpaired ligand (JAK/STAT), Eiger (JNK), and multiple elements of the IMD pathway. They also do not encode canonical antimicrobial peptides (AMPs) like defensins but possess putative homologs of ctenidins, AMPs previously identified in spiders and ticks, which may be adopted as a novel genetic readout for immune response in mites. Our findings lay the groundwork for future functional studies on mite immunity and open new avenues for RNAi-based biocontrol strategies targeting immune pathways to enhance Varroa management. Full article

The initial phase of an insect’s innate immune response to foreign pathogens is triggered by the identification of exogenous invaders, a mechanism facilitated by pattern recognition receptors. Among these receptors, peptidoglycan recognition proteins (PGRPs), abundant in insects, are essential components of the innate immune system. The roles of PGRPs have been extensively elucidated in Drosophila melanogaster; however, the mechanism underlying the immune response of Aedes albopictus to pathogens is unclear. Herein, we successfully cloned the full-length cDNA of a PGRP gene from Ae. albopictus, designated as the AaPGRP-LB gene. The open reading frame of AaPGRP-LB encodes 203 amino acids, including a secretion signal peptide and a canonical PGRP conserved domain. Multisequence alignment revealed that AaPGRP-LB possesses the amino acid residues essential for zinc binding and amidase activity. Molecular docking studies demonstrated that AaPGRP-LB exhibits a strong binding affinity for DAP-type and LYS-type peptidoglycan. The mRNA expression level of the AaPGRP-LB gene significantly increased after oral infection with Escherichia coli or Staphylococcus aureus. The purified recombinant AaPGRP-LB (rAaPGRP-LB) exhibited strong agglutination properties and demonstrated significant antimicrobial efficacy against E. coli and S. aureus in the presence of zinc ions. This study highlights the critical role of AaPGRP-LB in the immune response of Ae. albopictus. These findings provide a foundation for future research on mosquito immune pathways for innovative vector control and disease prevention strategies. Full article

Peptidoglycan recognition proteins (PGRPs) are a class of pattern recognition receptors (PRRs) that activate the innate immune system in response to microbial infection by detection of peptidoglycan, a distinct component of bacterial cell walls. Bioinformatic studies have revealed four PGRPs in the red imported fire ant Solenopsis invicta; nonetheless, the mechanism of the immune response of S. invicta induced by pathogens is still poorly understood. The peptidoglycan recognition protein full-length cDNA (designated as SiPGRP-S1/S2/S3/L) from S. invicta was used in this investigation. According to the sequencing analysis, there was a significant degree of homology between the anticipated amino acid sequence of SiPGRPs and other members of the PGRPs superfamily. Molecular docking studies demonstrated that SiPGRPs show strong binding affinity for a variety of PGN substrates. Additionally, tissue distribution analysis indicated that SiPGRPs are primarily expressed in several tissues of naïve larvae, including fat body, hemocytes, head, and thorax, as detected by quantitative real-time PCR (RT-qPCR). Microbial challenges resulted in variable changes in mRNA levels across different tissues. Furthermore, the antibacterial effects of antimicrobial peptides (AMPs) produced by major ants infected with Metarhizium anisopliae were assessed. These AMPs demonstrated inhibitory effects against M. anisopliae, Staphylococcus aureus, and Escherichia coli, with the most pronounced effect observed against E. coli. In conclusion, SiPGRPs act as pattern recognition receptors (PRRs) that identify pathogens and initiate the expression of AMPs in S. invicta, this mechanism contributes to the development of biopesticides designed for the targeted control of invasive agricultural pests. Full article

C-type lectins in organisms play an important role in the process of innate immunity. In this study, a C-type lectin belonging to the DC-SIGN class of Micropterus salmoides was identified. MsDC-SIGN is classified as a type II transmembrane protein. The extracellular segment of MsDC-SIGN possesses a coiled-coil region and a carbohydrate recognition domain (CRD). The key amino acid motifs of the extracellular CRD of MsDC-SIGN in Ca²⁺-binding site 2 were EPN (Glu-Pro-Asn) and WYD (Trp-Tyr-Asp). MsDC-SIGN-CRD can bind to four pathogen-associated molecular patterns (PAMPs), including lipopolysaccharide (LPS), glucan, peptidoglycan (PGN), and mannan. Moreover, it can also bind to Gram-positive, Gram-negative bacteria, and fungi. Its CRD can agglutinate microbes and displays D-mannose and D-galactose binding specificity. MsDC-SIGN was distributed in seven tissues of the largemouth bass, among which the highest expression was observed in the liver, followed by the spleen and intestine. Additionally, MsDC-SIGN was present on the membrane of M. salmoides leukocytes, thereby augmenting the phagocytic activity against bacteria. In a subsequent investigation, the expression patterns of the MsDC-SIGN gene and key genes associated with the TLR signaling pathway (TLR4, NF-κB, and IL10) exhibited an up-regulated expression response to the stimulation of Aeromonas hydrophila. Furthermore, through RNA interference of MsDC-SIGN, the expression level of the DC-SIGN signaling pathway-related gene (RAF1) and key genes associated with the TLR signaling pathway (TLR4, NF-κB, and IL10) was decreased. Therefore, MsDC-SIGN plays a pivotal role in the immune defense against A. hydrophila by modulating the TLR signaling pathway. Full article

Insects possess an effective immune system, which has been extensively characterized in several model species, revealing a plethora of conserved genes involved in recognition, signaling, and responses to pathogens and parasites. However, some taxonomic groups, characterized by peculiar trophic niches, such as plant-sap feeders, which are often important pests of crops and forestry ecosystems, have been largely overlooked regarding their immune gene repertoire. Here we annotated the immune genes of soft scale insects (Hemiptera: Coccidae) for which omics data are publicly available. By using immune genes of aphids and Drosophila to query the genome of Ericerus pela, as well as the transcriptomes of Ceroplastes cirripediformis and Coccus sp., we highlight the lack of peptidoglycan recognition proteins, galectins, thaumatins, and antimicrobial peptides in Coccidae. This work contributes to expanding our knowledge about the evolutionary trajectories of immune genes and offers a list of promising candidates for developing new control strategies based on the suppression of pests’ immunity through RNAi technologies. Full article