Search Results (150)

Heat shock proteins (HSPs) play a key role in enhancing insect resilience to abiotic and biotic stresses by preserving cellular integrity and modulating immune responses. This review summarizes the main functions of HSPs in insects, including protein stabilization, interaction with antioxidant systems, and involvement in the innate immune response. The expression of HSPs under environmental conditions reflects their evolutionary adaptation to various stressors, including thermal changes, chemical exposure, and pathogens. Future research should focus on the interaction between HSPs and other stress response systems to improve our understanding of insect adaptation. Furthermore, in the context of global climate change, HSPs emerge as a crucial resilience factor and potential biomarkers for environmental monitoring. Full article

Insects rely on their innate immune system to defend against pathogens, and the Toll signaling pathway plays an important role in immune regulation. Our previous studies have shown that BmToll9-1 functions as a positive regulator in the Toll pathway. This study seeks to elucidate the role of BmToll9-1, as a sensor to bacterial challenge, in modulating larval development and downstream Toll signaling pathways. Silkworm larvae were subjected to infection with either Gram-negative Escherichia coli or Gram-positive Staphylococcus aureus bacteria following silencing of BmToll9-1 by RNA interference (RNAi). This bacterial challenge triggered a compensatory re-induction of BmToll9-1 expression, which resulted in the recovery of larval weight and size to levels observed in untreated controls. Furthermore, upon bacterial infection of BmToll9-1-silenced larvae, there was an up-regulation in the expression of both signaling genes in the Toll pathway and downstream effector genes, with a marked preference for Gram-negative bacteria. These results highlight the involvement of BmToll9-1 in the Toll signaling pathway as a positive regulator, influencing silkworm development. Additionally, BmToll9-1 and BmToll9-2 were cross-validated to be genetically distinct genes, even though they were confirmed to be functionally analogous in the silkworm. Full article

The northern region of Brazil is endemic for American Tegumentary Leishmaniasis (ATL) primarily caused by Leishmania guyanensis and transmitted by the sand fly Nyssomyia umbratilis. The disease occurs at different rates in the municipalities of Manacapuru (MAN) and Rio Preto da Eva (RPE), located in the state of Amazonas. Despite their geographic proximity and separation by the Rio Negro, MAN has a low incidence, whereas RPE reports a significantly higher number of cases. Since the vector is present in both locations, potential biological differences in N. umbratilis may influence transmission. Previous studies suggested genotypic and phenotypic differences in N. umbratilis from both localities. To investigate the molecular factors underlying their potentially differential vectorial capacities, we performed a comparative proteomic analysis of dissected insect intestines from both localities. Our results revealed that sand flies from MAN showed a higher abundance of proteins related to gene transcription, protein translation, amino acid and proton transport, innate immune response and intestinal motility. Since the importance of microbiota has previously been shown in parasite–vector interactions, we also identified bacteria from both vector populations. We detected bacteria specific to each population and, exclusively in MAN, some species described in the literature as having parasiticidal properties. These findings highlight molecular and microbial peculiarities that could contribute to the observed difference in ATL prevalence in the two areas. 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

Background: Heterorhabditis bacteriophora entomopathogenic nematodes are commonly used in agricultural practices for the biological control of insect pests. These parasites are also used in basic research for unveiling the molecular basis of nematode parasitism in relation to the insect anti-nematode response. We have recently shown that H. bacteriophora excreted–secreted products reduce the expression of the antimicrobial peptide gene Diptericin in Drosophila melanogaster, which increases fly mortality due to enhanced propagation of the mutualistic bacteria Photorhabdus luminescens. However, the effect of entomopathogenic nematode extracellular vesicles (EVs) on the insect host defense remains unknown. Methods: Here, we injected adult flies with H. bacteriophora EVs and used quantitative RT-PCR together with gene-specific primers to analyze the activity of immune-related signaling pathways. Results: We found that H. bacteriophora EVs are lethal to Drosophila melanogaster, and they downregulate the expression of Attacin, Cecropin, and Prophenoloxidase 3 in adult flies. Conclusions: These findings build on previous knowledge and strengthen the notion that H. bacteriophora entomopathogenic nematodes release a variety of effector molecules to modify the insect’s innate immune signaling. This information is important because it contributes toward clarifying the molecular interplay between entomopathogenic nematode components and the host’s innate immune system. Full article

Serine proteases are widely distributed in both invertebrates and vertebrates, playing critical roles in the regulation of innate immunity. In the insect innate immune system, two pivotal pathways—the prophenoloxidase (PPO) activation cascade and Toll pathway-mediated antimicrobial peptide (AMP) synthesis—are both tightly regulated by serine protease cascades. This study focuses on serine protease–hemolymph protease 6 of A. pernyi (Ap-HP6). Following immune stimulation, the expression of Ap-proHP6 was significantly induced, primarily observed in hemocytes and the fat body. After suppressing Ap-proHP6 expression via RNA interference (RNAi) and infecting larvae with different microbes, the expression levels of AMPs showed a downward trend. When endogenous Ap-proHP6 content in hemolymph was reduced using RNAi technology or anti-rAp-proHP6-His₆ polyclonal antibodies, PAMPs/microbe-mediated phenoloxidase (PO) activity significantly decreased. These results suggest that Ap-HP6 has a positive regulatory effect on PPO activation and AMP synthesis. Additionally, the in vitro hydrolysis of rAp-proHP6-Tb-His₆ yielded rAp-HP6 with serine protease activity, which exhibited optimal reaction conditions for S-2288 at pH 8.0, 50 °C, and 15 min. Full article

Mosquitoes, comprising over 300 species, are pivotal vectors for transmitting arthropod-borne viruses (arboviruses) to vertebrates via bites, posing a significant public health threat with approximately 700,000 annual deaths. In contrast, insect-specific viruses (ISVs) exclusively infect insects and have no direct impact on human health. Yunnan Province in China, located in tropical and subtropical regions, provides an ideal environment for mosquito habitation and has the highest diversity of known mosquito-borne viruses. In this study, mosquito samples were collected from eight cities and states in Yunnan Province, totaling 15,099 specimens. Based on the collection sites and mosquito species, the samples were divided into 110 groups for virus isolation. Four insect-specific viruses (Tanay virus [TANV], Culex orthoflavivirus [CxFV], Aedes orthoflavivirus [AeFV], La Tina virus [LTNV]) were successfully isolated, and co-infection studies with dengue virus (DENV-2) were conducted in C6/36 cells. Preliminary results suggested that these four insect-specific viruses may reduce the viral titer of DENV-2 in C6/36 cells. Understanding the intricate interactions between insect-specific viruses and mosquito-borne viruses is crucial for elucidating the multifaceted role of mosquitoes in arboviral transmission dynamics. Insect-specific viruses exhibit considerable potential as innovative biocontrol agents, with promising capacity to attenuate mosquito-borne viral transmission through the targeted modulation of mosquito innate immunity and physiological adaptations. Full article

Insects detect pathogens through their germ-line encoded pattern recognition receptors (PRRs). Among these, β-1,3-glucan recognition protein (βGRP) is a crucial PRR that specifically identifies pathogenic microorganisms and triggers innate immune signaling cascades. However, it remains unclear whether βGRP can detect viruses and protect the host from viral threats. In this study, using high-throughput sequencing technology, we observed a significant suppression of βGRP-3 in Bombyx mori during infection with the Bombyx mori cytoplasmic polyhedrosis virus (BmCPV). Moreover, overexpression of βGRP-3 in BmN cell lines resulted in a reduction of BmCPV proliferation, whereas knockdown of βGRP-3 in BmN cells promoted BmCPV proliferation. These findings suggest that the βGRP family functions not only as anti-bacterial, antifungal, and anti-yeast PRRs but also as protectors against various harmful viruses in insects. Full article

Plants are challenged regularly with multiple types of biotic stress factors, such as pathogens or insect herbivores, in their environment. To detect and defend against pathogens, plants have evolved an innate immune system in which intracellular receptors in the so-called effector-triggered immunity play a vital role. In Arabidopsis thaliana the Toll/interleukin-1 receptors (TIRs) domain is related to intracellular immunity receptors, for example in TIR-NBS-LRR (TNL) proteins. Among the TIR domain carrying proteins, very little is known about the function of the TIR-X proteins. Here, we focus on the recently described TIR-X (TIRP; At5g44900) to analyze its role in phytohormone-mediated plant defense through gene expression and phytohormone quantification. Therefore, we employed two fungal pathogens, the necrotrophic Alternaria brassicicola and the hemibiotrophic Verticillium dahliae, to infect A. thaliana WT (Col-0), TIRP knock-out, and TIRP overexpressing lines for comparative analyses. Furthermore, we included the insect herbivore Spodoptera littoralis and a treatment with S. littoralis egg extract on the plants to analyze any role of TIRP during these attacks. We found that both A. brassicicola and V. dahliae infections increased TIRP gene expression systemically. The salicylic acid content was higher in the TIRP overexpressing line, corresponding to a better S. littoralis larval growth performance in feeding assays. However, since we never observed clear infection-related differences in jasmonate or salicylic acid levels between the wild type and the two transgenic Arabidopsis lines, our results rule out the possibility that TIRP acts via the regulation of phytohormone synthesis and accumulation. Full article

Unusual membrane-bound particles are present in the venom of the parasitoid wasps that parasitize Drosophila melanogaster. These venom particles harbor about 400 proteins and suppress the encapsulation of a wasp egg. Whereas the proteins in the particles of Leptopilina boulardi venom modify host hemocyte properties, those in L. heterotoma kill host hemocytes. The mechanisms underlying this differential effect are not well understood. The proteome of the L. heterotoma venom particles has been described before, but that of L. boulardi has not been similarly examined. Using sequence-based programs, we report the presence of conserved proteins in both proteomes with strong enrichment in the endomembrane and exosomal cell components. Extracellular vesicle markers are present in both proteomes, as are numerous toxins. Both proteomes also contain proteins lacking any annotation. Among these, we identified the proteins with structural similarity to the ADP-ribosyltransferase enzymes involved in bacterial virulence. We propose that invertebrate fluids like parasitoid venom contain functional extracellular vesicles that deliver toxins and virulence factors from a parasite to a host. Furthermore, the presence of such vesicles may not be uncommon in the venom of other animals. An experimental verification of the predicted toxin functions will clarify the cellular mechanisms underlying successful parasitism. 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

Cancer is a leading cause of death worldwide, characterized by uncontrolled cell growth and multiple mutations. Chemotherapy is often associated with harmful side effects, and cancer cells may become resistant through various mechanisms. New approaches, which are able to address both the toxicity and resistance issues of chemotherapy, are of primary importance in cancer research. Antimicrobial peptides (AMPs), naturally occurring molecules in the innate immune system of all living organisms, have a wide spectrum of cytotoxic activities against cancer cells and could be a promising alternative to actual chemotherapeutics. Here, we tested peptide fractions, rich in AMPs, extracted from the hemolymph of the larvae of the insect Hermetia illucens on the HT29 and HCT116 human colorectal cancer cells, observing cell growth inhibition by cell accumulation in the G2/M phase and increased apoptosis. Furthermore, the peptide extract induced a significant cytoskeleton reorganization, resulting in reduced motility. These effects were more evident with the peptide fractions obtained from the Escherichia coli-infected larvae. The peptide fractions also enhanced the effects of traditional chemotherapeutics. Overall, the results obtained suggest the presence of biologically active molecules in the hemolymph of H. illucens larvae, confirming that insect-derived peptides are a promising research area in oncology. Full article

Gastric cancer (GC) is one of the leading causes of cancer-related mortality worldwide, characterised by poor prognosis and limited responsiveness to chemotherapy. There is a need for new and more effective anticancer agents. Antimicrobial peptides (AMPs) represent a promising class of biomolecules for this purpose. Naturally occurring in the innate immune system, these peptides can also exert cytotoxic effects against cancer cells, earning them the designation of “anticancer peptides” (ACPs). They have the potential to be a viable support for current chemotherapy schedules due to their selectivity against cancer cells and minor propensity to induce chemoresistance in cells. Insects are an excellent source of AMPs. Among them, due to its ability to thrive in hostile and microorganism-rich environments, we isolated a peptide fraction from Hermetia illucens L. (Diptera: Stratiomyidae) haemolymph to evaluate a possible anticancer activity. We tested Peptide Fractions (PFs) against AGS and KATO III gastric cancer cell lines. Data obtained indicated that PFs, especially those resulting from Escherichia coli and Micrococcus flavus infection (to boost immune response), were able to inhibit tumour cell growth by inducing apoptosis or cell cycle arrest in a cell line-specific manner. These results support further investigation into the use of antimicrobial peptides produced from insects as possible anticancer agents. Full article

The insect NF-κB pathway is primarily constituted by nuclear factor κB (NF-κB) and the inhibitor of κB (IκB), which plays a crucial role in the innate immune response. Dorsal and Cactus, as NF-κB and IκB factors, are important downstream regulators of the Toll pathway in Plutella xylostella. In this study, the PxDorsal and PxCactus genes of P. xylostella were cloned, and the molecular docking demonstrated that PxDorsal and PxCactus can interact with each other. RT-qPCR results indicated that PxDorsal and PxCactus were expressed in all stages, and the expression of PxDorsal, PxCactus, and antimicrobial peptides PxGloverin2, PxMoricin3, and PxLysozyme2 were significantly down-regulated under Bacillus thuringiensis (Bt8010) infection. Interestingly, silencing the PxDorsal gene by RNA interference (RNAi) significantly down-regulated the expression of PxGloverin2 and PxMoricin3 and increased the epidermis melanization of P. xylostella larvae fed with Bt8010. Our findings indicate that PxDorsal and PxCactus may interact with each other, and silencing PxDorsal inhibits the expression of downstream antimicrobial peptides, thereby enhance the susceptibility of P. xylostella to Bt8010. This study contributes a theoretical basis for further research on the Toll pathway of P. xylostella to pathogens and offers insights for screening effective biological control targets from the perspective of the immune system. Full article

Melanogenesis and melanin deposition are processes essential for the effective immune response of insects to various invaders. Phenoloxidase (PO), produced in specialized cells as an inactive precursor prophenoloxidase (proPO), is the key enzyme for melanin formation. The precursor is activated via limited proteolysis by a dedicated serine proteinase, which is the final element in the cascade of serine proteinases (SPs) that make up the PO system. Melanogenesis provides different cytotoxic molecules active in fighting infections, as well as melanin, which is important for sequestration of invaders. However, since the cytotoxic reactive compounds generated during melanization also pose a threat to host cells, strict control of the PO system is necessary for host self-protection. Different pathogens and parasites influence the PO system and melanization through various strategies, which allow them to survive and develop in the host insect body. In this review, we characterize “the lights and shadows” of PO system activation, indicating, on one hand, its advantages as an efficient and effective mechanism of the insect immune response and, on the other hand, the dangers for the insect host associated with the improper functioning of this system and selected strategies for regulating its activity by entomopathogenic organisms. Full article