Insect antimicrobial peptides and their applications

Shifts in sex-specific immune gene expression in a beetle with parental care

Males and females generally differ in resource investment strategies in order to maximise reproductive output. These strategies involve the control of important systemic processes such as self-maintenance and immune activity, which in turn could be traded-off against aspects of reproduction in a sex-specific manner. While some aspects of this immunomodulation have been previously shown in domestic animals, sex-specific immune modulation using repeated sampling over the breeding period has rarely been tested in the wild. Here we used Lethrus apterus, a sexually dimorphic beetle with parental care, to investigate the association between sex roles (e.g. offspring provisioning) and sex-specific immune gene expression. By determining the immune gene activation of males and females at five successive moments within the active season, we found that their sex-specific immune gene expression varies substantially across the active season, alternating between male bias to female bias and vice versa. Though, when pooling all sampling dates together, there was no overall difference in the number of up-regulated immune genes between the sexes. Sex roles in this beetle are associated with energetically demanding behaviours that could potentially explain our results. We highlight the importance of successive sampling protocols to understand ecological dynamics in the wild.

Time-series RNA sequencing reveals that immulectin-1 (IML-1) is a potential target for biological control of fall armyworm, Spodoptera frugiperda

Insects mount robust immune responses to reduce the efficacy of biopesticides. Identification of critical immune targets for biocontrol strategies is thus essential. However, immune targets in the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), a major pest of corn, remain largely unexplored. Here, we investigated the immune response of S. frugiperda to the entomopathogen Beauveria bassiana (Hypocreales: Cordycipitaceae). Time-series RNA sequencing revealed 863, 717, and 165 differentially expressed genes (DEGs) at 24, 48, and 60 h post-infection, respectively. GO and KEGG enrichment analyses revealed that DEGs were significantly enriched in immune-related terms and pathways. Among the DEGs, the gene encoding immulectin SfIML-1, a C-type lectin with dual carbohydrate recognition domains, was significantly upregulated during the early and intermediate stages of infection. Genome-wide analysis identified nine IML genes, with SfIML-1 as the only one highly responsive to B. bassiana. Recombinant SfIML-1 binds pathogen-associated molecular patterns and pathogens, enhancing cellular responses. RNAi of SfIML-1 decreased survival after fungal infection, while injection of recombinant SfIML-1 increased survival. Suppression of the NF-κB and JAK-STAT pathways diminished SfIML-1 expression in both fat body and Sf9 cells. These results identify SfIML-1 as a key pattern recognition receptor and a promising target for developing novel biocontrol strategies.

PxSpätzle3 Regulates the Toll Pathway To Affect Bacillus thuringiensis Susceptibility of Plutella xylostella

Spätzle is an important messenger in the Toll pathway of the insect innate immune system. However, the function of Spätzle in regulating the Toll pathway in Bacillus thuringiensis (Bt) susceptibility of Plutella xylostella is unclear. In this study, we cloned the Spätzle3 gene of P. xylostella. Molecular docking and yeast two-hybrid experiments indicated that PxSpätzle3 combined with PxToll6 to regulate the Toll pathway. After knocking out PxSpätzle3, the expression of downstream Toll pathway genes and antimicrobial peptides (AMPs) decreased. Antibacterial assays showed that PxGloverin2 could inhibit Bt8010. Further bioassays revealed that the susceptibility of the mutant to Bt8010 was significantly higher than that of the wild type. Intriguingly, the gut bacteria Enterobacter sp. EbPXG5 enhanced the lethality of Bt8010 to the mutant P. xylostella. Our findings clarify that PxSpätzle3 activates the Toll pathway by binding with PxToll6, regulates AMP production, and affects the susceptibility of P. xylostella to Bt8010. Additionally, our study uncovers the role of gut bacteria in this process. These insights provide new ideas for the sustainable control of pests.

Biological Activity of Peptide Fraction Derived from Hermetia illucens L. (Diptera: Stratiomyidae) Larvae Haemolymph on Gastric Cancer Cells

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.

Single Amino Acid Changes Impact the Ability of Drosophila melanogaster Cecropins to Inhibit Growth of Providencia Pathogens

As antibiotic-resistant bacteria spread worldwide, the need to develop novel antimicrobial agents is urgent. One rich source of potential antimicrobials is the insect immune system, as insects produce a wide range of antimicrobial peptides (AMPs) with diverse sequences and structures. Insects also encounter many bacterial pathogens, some of which are closely related to pathogens of clinical relevance. However, despite interest in AMPs as therapeutics, the relationships between the amino acid sequence, biophysical properties, antimicrobial activity, and specificity are still not generalizable. To improve our understanding of these relationships, we assessed how single amino acid changes in cecropin AMPs produced by the fruit fly, Drosophila melanogaster, impact both their structure and their ability to inhibit the growth of Providencia species isolated from wild-caught D. melanogaster. These pathogens are of particular interest as they have a range of virulence in fruit flies, and work in vivo suggests that differences in virulence could be partially attributable to differential susceptibility to AMPs. D. melanogaster cecropins are 40 amino acids long but vary at only 5 residues with largely conservative changes. We found that these changes could impact inhibitory concentrations by up to 8-fold against Providencia species. Our investigation focused on a single amino acid position due to the importance of a flexible "hinge" in cecropin function. We found that altering the identity of this amino acid alone greatly impacted antimicrobial activity, changing bacterial susceptibility up to 16-fold. Generally, Providencia species that are less virulent in vivo are more susceptible to cecropin AMPs in vitro. We also observed differences in the kinetics of permeabilization and bacterial killing between species, suggesting that peptide-membrane interactions were differently affected by single amino acid changes and that bacteria in this genus may vary in their membrane composition.

Bioactive peptides derived from insect proteins: Preparation, biological activities, potential applications, and safety issues

Bioactive peptides are polypeptides with specific amino acid sequences that exhibit biological activities and health benefits. Insects have emerged as a sustainable source of proteins in human food and animal feed due to their efficient resource utilization, low environmental footprint, and good nutritional profile. Moreover, insect-derived bioactive peptides (IBPs) offer potential applications in functional foods and pharmaceuticals due to their antioxidant, antimicrobial, antihypertensive, anti-inflammatory, antidiabetic, and anti-obesity activities. In this article, the isolation, purification, and properties of IBPs are reviewed, as well as their potential health benefits, commercial applications, and safety. Despite the growing interest in incorporating IBPs into food products, challenges regarding consumer acceptance, safety, and regulations still persist. Thus, there is a pressing need for further research in this area, as well as clarification of the regulatory framework, before the full potential of insects as a sustainable source of bioactive peptides for human consumption can be realized.

The first Ranatuerin antimicrobial peptide with LPS-neutralizing and anti-inflammatory activities in vitro and in vivo

Pelophylax nigromaculata, common traditional Chinese medicinal material used for several hundreds of years, is one of the most widely distributed amphibians in China. In this study, a novel Ranatuerin-2 family antimicrobial peptide, Rana-2PN, was identified and characterized from its skin, and its structural characteristics and functional activities were studied extensively. First, Rana-2PN exhibited a broad spectrum of antimicrobial activity, displaying minimum inhibitory concentration (MIC) values ranging from 12.5 to 100 μM against all strains tested. Mechanistically, Rana-2PN exerted its bacteriostatic effects by binding to bacterial cells and inducing bacterial membrane rupture and subsequent bacterial death. Secondly, Rana-2PN effectively inhibited the inflammatory response in RAW264.7 cells induced by lipopolysaccharide (LPS) and reduced inflammation induced by carrageenan in mouse toes. Thus, Rana-2PN with LPS-neutralizing, anti-inflammatory, and antimicrobial properties, represents the first member of the Ranatuerin antimicrobial peptide family, and its discovery offers a promising therapeutic candidate for addressing inflammatory disorders resulting from bacterial infections.

Research on the Expression of Immune-Related Genes at Different Stages in the Third-Instar Larvae of Spodoptera frugiperda Infected by Metarhizium rileyi

Spodoptera frugiperda is a major migratory agricultural pest that poses a significant threat to global crop safety. Metarhizium rileyi has emerged as an effective biocontrol agent against lepidopteran pests. In this study, we examined the immune responses of third-instar S. frugiperda larvae at various stages of an M. rileyi infection. Using RNA-seq and microscopic observation, we identified the immune-related pathways enriched at different infection stages, which were further validated by a qRT-PCR. Our findings revealed the following immune responses during infection: During the stage when M. rileyi penetrated the host cuticle (0-48 h), the genes related to energy metabolism, detoxification, and melanization were upregulated. Meanwhile, the TOLL and IMD signaling pathways were activated to counter the infection. During the stage of M. rileyi's internal infection (48-96 h), which was the peak expression period of the immune-related genes, cellular immunity predominated. Hemocytes encapsulated and phagocytosed the hyphal bodies. Phagocytosis was enhanced through the upregulation of the genes related to ROS and the melanization-related genes, as well as the genes involved in insect hormone biosynthesis. During the stage when M. rileyi grew from the inside to the outside of the host (96-120 h), immune system paralysis resulted in host mortality. These findings deepen our understanding of the immune interactions between M. rileyi and S. frugiperda, support the potential of M. rileyi as an effective biocontrol agent, and provide a theoretical foundation for the development of targeted biopesticides for pests using biotechnological approaches.

Characterization and functional analysis of Spodoptera litura galectins

BACKGROUND

Insects rely on their effective innate immune system to defend against pathogen infection, and pattern recognition receptors (PRRs) play a crucial role in insect immunity. Galectins, a family of animal β-galactoside-binding lectins, may serve as PRRs. Mammalian galectins are involved in diverse physiological processes; however, less is known about functions of insect galectins.

RESULT

In this study, we focused on an agricultural pest Spodoptera litura and identified a total of 13 Slgalectins, and a functional study of Slgalectin-4 and Slgalectin-7 was conducted. Both recombinant Slgalectin-4 and Slgalectin-7 proteins directly bound to Bacillus thuringiensis and an entomopathogenic fungus Metarhizium rileyi. Importantly, supplementing recombinant Slgalectin-4 to S. litura larvae significantly increased larval survival after M. rileyi infection but accelerated larvae death after B. thuringiensis infection, whereas supplementing Slgalectin-7 increased larval survival after B. thuringiensis infection but did not influence larval survival after M. rileyi infection. Supplementing both Slgalectin-4 and Slgalectin-7 altered the expression of some antimicrobial peptide genes in larval hemocytes after microbial infection, which may partly account for the roles of Slgalectin-4 and -7 in larval survival.

CONCLUSION

Our findings revealed that Slgalectin-4 and -7 may serve as PRRs to bind different pathogens and alter expression of immune effector genes such as antimicrobial peptide genes, eventually modulating immune responses of S. litura larvae to pathogens such as B. thuringiensis and M. rileyi. © 2025 Society of Chemical Industry.

Bioactive compounds in edible insects: Aspects of cultivation, processing and nutrition

The increasing interest in edible insects, driven by projected global population growth and environmental concerns, has led to the exploration of their potential in the food sector. Edible insects are abundant in macronutrients, such as proteins, lipids and chitin, as well as micronutrients, such as minerals, vitamins and phenolic compounds. Considering their content of bioactive compounds, they offer a sustainable solution to meet future food demands while providing potential health benefits. This review identifies bioactive peptides, phenolic compounds, chitosan, and vitamins as major bioactive ingredients derived from insects. It discusses their presence in various edible insect species, their primary bioactive properties, and methods for production and isolation. Bioactive compounds sourced from edible insects exhibit antioxidant, antimicrobial, and disease-preventing properties. Insects also serve as rich sources of vitamins A, B2, B6, B12, D, and E, albeit with variations in content among species and life stages. However, the consumption of insects poses risks related to their biological and chemical contaminants, as well as their allergenicity. Managed diets in farm-bred insects ensure controlled nutrient levels, highlighting their potential as sustainable sources of bioactive compounds for human health. Adequate processing and labeling of insect-derived products can reduce the risk of insect consumption. In conclusion, the bioactive compound profile of edible insects complements their nutritional richness and highlights their potential to address future nutrition and food security.

Novel antimicrobial defensin peptides from different coleopteran insects (Coleoptera: Insecta): identification, characterisation and antimicrobial properties

Antimicrobial peptides are crucial components of the immune systems of both vertebrates and invertebrates. Here, defensins, the most studied class of antimicrobial molecules in arthropods were investigated in four coleopteran insect species: Harpalus rufipes (DeGeer, 1774), Mylabris quadripunctata (Linnaeus, 1767), Sphaeridium marginatum (Linnaeus, 1758), and Ocypus mus (Brullé, 1832). The peptides synthesized with over 95% purity and their antimicrobial activities were evaluated by MIC test method. As a result, it was determined that Mylabris quadripunctata defensin (MqDef) showed high antimicrobial activity against Staphylococcus aureus and MRSA, whereas Sphaeridium marginatum (SmDef) and Harpalus rufipes (HrDef) defensins against Candida tropicalis.

Galleria mellonella (Greater Wax Moth) as a Reliable Animal Model to Study the Efficacy of Nanomaterials in Fighting Pathogens

The spread of multidrug-resistant microbes has made it necessary and urgent to develop new strategies to deal with the infections they cause. Some of these are based on nanotechnology, which has revolutionized many fields in medicine. Evaluating the safety and efficacy of these new antimicrobial strategies requires testing in animal models before being tested in clinical trials. In this context, Galleria mellonella could represent a valid alternative to traditional mammalian and non-mammalian animal models, due to its low cost, ease of handling, and valuable biological properties to investigate host-pathogen interactions. The purpose of this review is to provide an updated overview of the literature concerning the use of G. mellonella larvae as an animal model to evaluate safety and efficacy of nanoparticles and nanomaterials, particularly, of those that are used or are under investigation to combat microbial pathogens.

Drug Discovery Potential of Insect-derived Compounds: A Review

Insects are the most numerous and diverse collection of organisms on earth. Around the world, human societies have utilised insects and the materials derived from them as medical resources. These arthropods use chemistry, like all other species. According to their survival needs, they make adaptations, including protecting themselves from infection as well as predation, being able to connect with a social life, and carrying out generations with survivability in the environment. The main focus of the study of chemical ecology is the abundance of chemical compounds found in arthropods that are used for these ecological adaptations. This thorough analysis summarises the huge potential for finding new natural compounds with medical benefits from the Arthropods. Insects and their derivatives have a wide range of uses, and their "raw products" have made significant strides in a wide range of industries, including pharmaceuticals, tissue engineering, dentistry, plant and agricultural science, veterinary medicine, cosmetics, and cosmeceuticals, food, and nutraceuticals, among others. Bioactive components derived from insects are emerging as potential therapeutic sources that are beneficial against a variety of disorders. Insects, which have a huge variety of species, are an intriguing and potential source of low molecular biologically active natural compounds that are either produced by the insect itself or by accompanying microbes. The present review work collated the updates of insect-derived compounds, the use of insects worldwide, and drug discovery potential of insect derivatives.

Honeybee defense mechanisms: Role of honeybee gut microbiota and antimicrobial peptides in maintaining colony health and preventing diseases

Honeybees play a vital role in pollination and the maintenance of ecosystem biodiversity, making their health and well-being crucial for agriculture and environmental sustainability. Bee health is modulated by symbiotic microorganisms colonizing the gut in balanced proportions. Studies have demonstrated that these beneficial bacteria have the capacity to enhance the immune system of honey bees, having substantial impact on regulating their immunological responses and hence aiding in defending against pathogenic illnesses. Another important aspect of honeybee health is their innate immune system that is related to their ability to synthesize antimicrobial peptides (AMP). AMPs, the small, cationic peptides are the humoral effector molecules that are synthesized in the hemolymph of the insects after being exposed to microbial infectious agents. A number of honeybee's gut microbiota especially Lactic Acid Bacteria (LAB), are known to regulate the production of several AMPs and hence are able to provide protection to these insects against a number of disease agents by modulating their innate immune response via induction of the AMPs genes. These AMPs mainly produced by adult workers are an important and integral part of an insect's immune response. Several AMPs namely apidaecins, abaecins, hymenoptaecins and defensins produced in the adult honeybee, hold the ability to control or prevent a number of diseases in these pollinator insects.

Insect Brain Proteomics: A Case Study of Periplaneta americana

Insects are known invertebrate species with economic, ecological, pathological, and medicinal value, as well as closely associated with human populations. Entomophagy and entomotherapy are future promising prospects largely attributable to the abundant availability, high protein content, and climatic sustainability of insects. In particular, the insect brain is an important system with a secluded, compact, and protective exoskeleton. It is immunologically privileged and capable of producing a robust immune response against pathogens. It is also a source of materials that initiate key activity throughout the body. Proteomic interrogation of Periplaneta americana enables understanding the role of this insect in the fields of food and pharmacology. Proximate analyses of P. americana highlights its richness in proteins. Here we perform a simple proteomic analysis to study the brain proteome of P. americana. The processes applied during the study include gel-based isolation and separation of proteins, followed by NanoLC-MS (Orbitrap) analyses and bioinformatic interrogation of the data. The results demonstrated that this insect proteome comprises antimicrobial proteins, allergens, and proteins required for metabolic processes.

Low-Fat Tenebrio molitor Meal as a Component in the Broiler Diet: Growth Performance and Carcass Composition

Tenebrio molitor is considered a sustainable protein source for diets in poultry. It has been investigated in regard to the performance, health status, and product quality in different poultry species. This study was designed to evaluate the effect of low-fat Tenebrio molitor meal (LFTM) included in the broilers' diet on the growth performance and carcass composition of the birds. The trial was conducted at the Institute of Animal Science-Kostinbrod, Bulgaria. A total of 120 male one-day-old Ross 308 broilers were allocated to 5 groups. After an adaptation period of 14 days, the birds were fed a basal diet (C) and diets including LFTM in amounts of 2.5% (T2.5), 5% (T5), 7.5% (T7.5), and 10% (T10). The growth performance of the birds was measured during the trial. At 35 days of age, 8 birds per group were slaughtered, and their carcass quality was evaluated. We found a linear response of BWG and FCR towards the inclusion of Tenebrio molitor meal (TM) in the diet. For the whole period (14-35 d), the BWG decreased (p = 0.0002), while the values of FCR increased (p = 0.0001) with the increase in the levels of the insect meal. The doses of 7.5% and 10% of the insect meal were associated with lower carcass weight and also decreased the yield of the breast. The results of the study indicated that the incorporation of LFTM, especially in amounts of 7.5-10%, could not be appropriate for broilers due to adverse effects on the growth performance and carcass composition.

Comparison of the effect of bacterial stimulation on the global epigenetic landscape and transcription of immune genes in primarily zoophilic members of the Anopheles gambiae complex (Diptera: Culicidae)

Members of the Anopheles gambiae complex vary in their vector competence, and this is often attributed to behavioural differences. Similarly, there are differences in transmission capabilities of the zoophilic members of this complex despite exhibiting similar behaviours. Therefore, behavioural differences alone cannot fully explain vector competence variation within members of the An. gambiae complex. The immune system of mosquitoes plays a key role in determining susceptibility to parasite infection and consequently transmission capacity. This study aimed to examine variations in the immune response of An. arabiensis, An. merus and An. quadriannulatus, a major, minor, and non-vector respectively. The global epigenetic landscape was characterised and the expression of Defensin-1 and Gambicin was assessed in response to Gram-positive (Streptococcus pyogenes) and Gram-negative (Escherichia coli) bacterial infections. The effect of insecticide resistance in An. arabiensis on these aspects was also assessed. The immune system was stimulated by a blood-borne bacterial supplementation. The 5mC, 5hmC, m6A methylation levels and Histone Acetyl Transferase activity were assessed with commercial ELISA kits. The transcript levels of Defensin-1 and Gambicin were assessed by quantitative Real-Time Polymerase Chain Reaction. Species-specific differences in 5mC and m6A methylation existed both constitutively as well as post immune stimulation. The epigenetic patterns observed in the laboratory strains were largely conserved in F1 offspring of wild-caught adults. The methylation patterns in the major vector typically differed from that of the minor/non-vectors. The differences between insecticide susceptible and resistant An. arabiensis were more reflected in the expression of Defensin-1 and Gambicin. The expression of these peptides differed in the strains only after bacterial stimulation. Anopheles merus and An. quadriannulatus expressed significantly higher levels of antimicrobial peptides, both constitutively and after immune stimulation. These findings suggest molecular variations in the immune response of members of the An. gambiae complex.

Defensins of the Stable Fly (Stomoxys calcitrans) have Developmental-Specific Regulation and Evolve at Different Rates

Organisms produce antimicrobial peptides (AMPs) either in response to infection (induced) or continuously (constitutively) to combat microbes encountered during normal trophic activities and/or through pathogenic infections. The expression of AMPs is tightly regulated, often with specificity to particular tissues or developmental stages. As a result, AMPs face varying selective pressures based on the microbes the organism's tissue or developmental stage encounters. Here, we analyzed the evolution and developmental-specific expression of Defensins, which are ancient AMPs in insects, in the stable fly (Stomoxys calcitrans). Stable fly larvae inhibit microbe-rich environments, whereas adult flies, as blood-feeders, experience comparatively fewer encounters with diverse microbial communities. Using existing RNA-seq datasets, we identified six Defensins that were only expressed in larvae (larval Defensins) and five that were not expressed in larvae (non-larval Defensins). Each of the non-larval Defensins was expressed in at least one adult tissue sample. Half of the larval Defensins were induced by mating or feeding in adults, and all three of the induced Defensins were located downstream of canonical binding sites for an Imd transcription factor involved in the highly conserved NF-κB signaling that regulates induction of AMPs. The larval and non-larval Defensins were located in distinct genomic regions, and the amino acid sequences of the larval Defensins formed a monophyletic clade. There were more amino acid substitutions across non-larval Defensins, with multiple genes losing a highly conserved furin cleavage site thought to be required for the removal of the amino terminus from the mature Defensin domain. However, larval Defensins had a higher proportion of radical amino acid substitutions, altering amino acid size and polarity. Our results reveal insights into the developmental stage-specific regulation of AMPs, and they suggest different regulatory regimes impose unique selection pressures on AMPs, possibly as a result of variation in exposure to microbial communities across development.

Discovery and characterization of a novel Lepidoptera-specific antimicrobial peptide from the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

Antimicrobial peptides (AMPs) are critical components of innate immunity in diverse organisms, including plants, vertebrates, and insects. This study identified and characterized a novel Lepidoptera-specific AMP, named lepidoptin, from the invasive pest Spodoptera frugiperda (Lepidoptera: Noctuidae). Lepidoptin is a 116-amino acid protein containing a signal peptide and a novel β-sandwich domain that is distinct from previously reported AMPs. Temporal and spatial expression analyses revealed a significant upregulation of the lepidoptin gene in vivo and in cultured SF9 cells in response to pathogens. Molecular docking analysis identified a specific binding cavity. Enzyme-linked immunosorbent assay and binding assays confirmed that lepidoptin can bind to pathogen-associated molecular patterns, bacteria, and fungi. Recombinant lepidoptin exhibited potent antibacterial activity by inducing bacterial agglutination, inhibiting bacterial growth, increasing bacterial membrane permeability, and preventing biofilm formation. Lepidoptin also showed antifungal activity against the entomopathogenic fungus Beauveria bassiana by inhibiting spore germination, increasing fungal cell permeability, and increasing reactive oxygen species. Injection of recombinant lepidoptin into S. frugiperda larvae increased survival after B. bassiana infection, whereas knockdown of lepidoptin by RNA interference decreased larval survival. In addition, lepidoptin showed antimicrobial activity against the plant pathogen Fusarium graminearum by inhibiting spore germination and alleviating disease symptoms in wheat seedlings and cherry tomatoes. This study demonstrates the remarkable dual functionality of lepidoptin in enhancing S. frugiperda immunity and controlling plant pathogens, making it a promising candidate for biocontrol strategies in both pest management and plant disease prevention.

Fatty acid synthase 2 knockdown alters the energy allocation strategy between immunity and reproduction during infection by Micrococcus luteus in Locusta migratoria

Immunity and reproduction are vital functions for the survival and population maintenance of female insects. However, owing to limited resources, these two functions cannot be fulfilled simultaneously, resulting in an energy tradeoff between them. Notably, the mechanisms underlying this immune-reproductive trade-off, in which energy competition likely plays a central role, remain poorly understood. Fatty acid synthase (FAS), a key gene involved in lipid synthesis and insect energy metabolism, was investigated in this study using Locusta migratoria as the research subject. Bacterial infection and RNA interference (RNAi) technology were used to examine changes in the immunity, fecundity, and energy metabolism patterns of locusts under different treatments. The findings of this study demonstrate that infection with Micrococcus luteus triggers an immune response in locusts, significantly upregulates the expression of defensin 3 (DEF3) and Attacin, and enhances pHenoloxidase (PO) activity. Upon FAS2 silencing, bacterial attack upregulated DEF3 and Attacin expression to a lesser extent, leading to increased lysozyme activity instead of PO. Furthermore, bacterial infection results in a decrease in glycogen and glucose content in the fat body, accompanied by a significant increase in triacylglycerol (TAG) content. However, after FAS2 knockdown, both the lipid and carbohydrate contents were significantly reduced in the fat body. Compared with bacterial infection alone, low FAS2 expression further exacerbated fecundity impairment in locusts. The expression levels of vitellogenin A (VgA) and vitellogenin B (VgB) were significantly low, with severe ovarian atrophy observed. Notably, the ovarian weight was only 21 % compared to that of the control group. Moreover, females exhibited minimal egg-laying behavior. In summary, our findings suggest that following FAS2 gene silencing, there is a greater inclination toward immune stimulation energy activation in locusts, whereas reproductive investment is reduced. The outcomes of this study will contribute to the further exploration of the molecular mechanisms underlying the trade-off between immune and reproductive energy in locusts.

The current state of research and potential applications of insects for resource recovery and aquaculture feed

Concerns about fishmeal use and its ecological footprints must be addressed for the aquaculture industry to move on as a sustainable food production sector. Through recent research outcomes, the insect-based meals in fish diets have promise and harnessed promises for commercial applications. In this midst, the efficiency of the selected insects in valorizing biological waste, as well as the nutritional profile of the harvested insects for use in fish diets, will be the driving forces behind such an approach. More extensive research has been published on the suitability of the waste substrate, the nutritional profiling of the meals, the level of substitution, the effects on growth, the immune physiology, and the flesh quality of the animals. Previously, there are only a few reviews available in insect protein applications in aqua feed that focused particularly on the nutritional quality and substitution levels. Considering the dearth of available work, the goal of this review is to provide a more comprehensive account of the resource recovery potential of insects and its derivatives, with a special emphasis on quality as determined by substrate used and processing techniques. Suggestions and policy implications for a sustainable approach to achieving a circular bio-economy of insect farming and its application in aquaculture are discussed for progression and advancement of the existing state of the art.

A Review of Antimicrobial Peptides: Structure, Mechanism of Action, and Molecular Optimization Strategies

Antimicrobial peptides (AMPs) are bioactive macromolecules that exhibit antibacterial, antiviral, and immunomodulatory functions. They come from a wide range of sources and are found in all forms of life, from bacteria to plants, vertebrates, and invertebrates, and play an important role in controlling the spread of pathogens, promoting wound healing and treating tumors. Consequently, AMPs have emerged as promising alternatives to next-generation antibiotics. With advancements in systems biology and synthetic biology technologies, it has become possible to synthesize AMPs artificially. We can better understand their functional activities for further modification and development by investigating the mechanism of action underlying their antimicrobial properties. This review focuses on the structural aspects of AMPs while highlighting their significance for biological activity. Furthermore, it elucidates the membrane targeting mechanism and intracellular targets of these peptides while summarizing molecular modification approaches aimed at enhancing their antibacterial efficacy. Finally, this article outlines future challenges in the functional development of AMPs along with proposed strategies to overcome them.

Identification of Multifunctional Putative Bioactive Peptides in the Insect Model Red Palm Weevil (Rhynchophorus ferrugineus)

Innate immunity, the body's initial defense against bacteria, fungi, and viruses, heavily depends on antimicrobial peptides (AMPs), which are small molecules produced by all living organisms. Insects, with their vast biodiversity, are one of the most abundant and innovative sources of AMPs. In this study, AMPs from the red palm weevil (RPW) Rhynchophorus ferrugineus (Coleoptera: Curculionidae), a known invasive pest of palm species, were examined. The AMPs were identified in the transcriptomes from different body parts of male and female adults, under different experimental conditions, including specimens collected from the field and those reared in the laboratory. The RPW transcriptomes were examined to predict antimicrobial activity, and all sequences putatively encoding AMPs were analyzed using several machine learning algorithms available in the CAMPR3 database. Additionally, anticancer, antiviral, and antifungal activity of the peptides were predicted using iACP, AVPpred, and Antifp server tools, respectively. Physicochemical parameters were assessed using the Antimicrobial Peptide Database Calculator and Predictor. From these analyses, 198 putatively active peptides were identified, which can be tested in future studies to validate the in silico predictions. Genome-wide analysis revealed that several AMPs have predominantly emerged through gene duplication. Noticeably, we detect a newly originated defensin allele from an ancestral defensin via the deletion of two amino acids following gene duplication in RPW, which may confer an enhanced resilience to microbial infection. Our study shed light on AMP gene families and shows that high duplication and deletion rates are essential to achieve a diversity of antimicrobial mechanisms; hence, we propose the RPW AMPs as a model for exploring gene duplication and functional variations against microbial infection.

Peptibodies: Bridging the gap between peptides and antibodies

Peptides are a very critical class of pharmaceutical compounds that can control several signaling pathways and thereby affect many physiological and biochemical processes. Previous research suggests that both peptides and antibodies may serve as potent tools for research, diagnostics, vaccination, and therapeutics across diverse domains. The distinct attributes of peptides, like their profound tissue penetration, efficient cellular internalization, reduced immunogenicity, and adaptability to chemical modification, underscore their significance in biomedical applications. However, they also possess drawbacks such as lower affinity, poor absorption, low stability to proteolytic digestion, and rapid clearance. The advent of peptibodies is a significant advance that improves the limitations of both peptides and antibodies. Peptibodies, or Peptide-Fc fusions, represent a promising therapeutic modality comprising biologically active peptides fused to an Fc domain. The stability and efficacy of the peptide are enhanced by this fusion strategy, which overcomes some of the inherent limitations. Many peptibodies have been developed to treat conditions like cancer, diabetes, and lupus. Romiplostim and Dulaglutide are the only ones approved by the EMA and FDA, respectively. Given the growing significance of peptibodies in the pharmaceutical landscape, this investigation aims to explain key aspects encompassing the intrinsic properties of peptides, the intricacies of peptibody production, and their potential therapeutic applications.

Effect of male parental gamma irradiation on host suitability of its F1 progeny of a lepidopteran tropical pest, Spodoptera litura (Fabr.) towards development and virulence of entomopathogenic nematodes, Steinernema thermophilum

The suitability of F1 progeny insect larvae of the irradiated male parent, Spodoptera litura (Fabr.) for infective juveniles (IJs) of entomopathogenic nematodes (EPN), Steinernema thermophilum was assessed to comprehend the feasibility of combining EPNs with nuclear pest control tactic. As compared to the control, the IJs induced faster host mortality with reduced proliferation in F1 host larvae. IJs derived from F1 host larvae exhibited almost similar proliferation capacity on normal hosts as in control. Further, the molecular basis of EPNs induced mortality in F1 host larvae was evaluated. Dual stress of EPN infection and irradiation induced downregulation of the relative mRNA expression of antimicrobial genes and upregulated expression of antioxidative genes. A pronounced effect of EPNs in association with irradiation stress was apparent on host mortality. Radiation induced sterile F1 insect larvae of S. litura acted as a reasonably suitable host for EPNs and also provided the environment for developing viable EPNs for their potential use as biocontrol agents.

A novel broad-spectrum antibacterial and anti-malarial Anopheles gambiae Cecropin promotes microbial clearance during pupation

Anophelinae mosquitoes are exposed to a variety of microbes including Plasmodium parasites that cause malaria. When infected, mosquitoes mount versatile immune responses, including the production of antimicrobial peptides. Cecropins are one of the most widely distributed families of antimicrobial peptides in insects and all previously studied Anopheles members are playing roles in adult mosquito immunity. We have identified and characterized a novel member of the Anopheles gambiae cecropin family, cecropin D (CecD), that is uniquely expressed and immune-responsive at late larval stages to promote microbial clearance through its broad-spectrum antibacterial activity during larval-pupal developmental transition. Interestingly, Cecropin D also exhibited highly potent activity against Plasmodium falciparum sporozoites, the malaria parasite stage that is transmitted from mosquitoes and infects humans and thereby holds promise as a malaria transmission-blocking agent. Finally, we have defined unequivocal cecropin-specific molecular signatures to systematically organize the diversity of the cecropin family in malaria vectors.

A tomato a day keeps the beetle away - the impact of Solanaceae glycoalkaloids on energy management in the mealworm Tenebrio molitor

Solanine (SOL), chaconine (CHA), and tomatine (TOM) are plant secondary metabolites produced mainly by the species of Solanaceae family, such as tomato Solanum lycopersicum L. These glycoalkaloids (GAs) have a wide range of biological activity, also in insects. However, their mechanisms of action are not precisely understood. The purpose of the study was to investigate how pure GAs and tomato leaf extract (EXT) affect glycolysis, Krebs cycle and β-oxidation of fatty acid pathways in Tenebrio molitor L. beetle. For this purpose, the larvae were injected with SOL, CHA, TOM, and EXT at two concentrations (10-8 and 10-5 M). For experiments, fat body, gut, and heamolymph samples were collected 2 and 24 h after injection. Then, the changes in the expression level of phosphofructokinase, citrate synthase, and β-hydroxyacyl-CoA dehydrogenase were measured using the RT-qPCR technique. The catalytic activity of these enzymes and the carbohydrate level in insects after GA treatment were determined by spectrophotometric method. Furthermore, the analysis of the amount of amino acids in tissues was performed with a GC-MS technique. The results obtained show that the GAs changed the activity and expression of the genes encoding key enzymes of crucial metabolic pathways. The effect depends on the type of GA compound, the tissue tested, and the incubation time after treatment. Furthermore, TOM and EXT affected trehalose concentration in the insect hemolymph and led to accumulation of amino acids in the fat body. The observed changes may indicate a protein degradation and/or enhanced catabolism reactions for the production of ATP used in detoxification processes. These results suggest that GAs alter energy metabolism in the mealworm T. molitor. The study contributes to our understanding of the mechanisms of action of secondary metabolites of plants in insects. This knowledge may allow the design of new natural biopesticides against insect pests because proper energy metabolism is necessary for the survival of the organism.

Protective effects of Chinese bayberry pomace wine against oxidative stress on Drosophila melanogaster

The Chinese bayberry pomace wine (CPW) was prepared with the assisted fermentation of lactic acid bacteria and acetic acid bacteria, and its antioxidant effect on Drosophila melanogaster was researched. After mixed fermentation, CPW had a better color, which means there was more retention of anthocyanins, and the functional activity of anthocyanins could enhance the antioxidant capacity of flies. We found that the lifespan of flies exposed to CPW was prolonged, and the reproductive capacity of these flies was decreased. The food intake of flies was also influenced by CPW with gender differences. Furthermore, CPW alleviated the excessive proliferation of the intestinal precursor cells of H2O2-induced flies and activated the transcription level of antibacterial peptide genes. CPW had a protective effect on H2O2-induced acute injury flies, with an increased survival rate, enhanced SOD and CAT activities, and decreased malondialdehyde (MDA) content in flies. The expression of oxidative stress-related genes including CuZn-SOD, Mn-SOD, and CAT was also significantly upregulated by CPW, but the downregulation effect of CPW on age-related gene expression such as methuselah (MTH), the target of rapamycin (TOR) and ribosomaiprotein S6 kinase (S6K) was sex-specific. These results suggested that CPW played an important role in anti-oxidative stress injury, which was beneficial to promoting the reuse of by-products from Chinese bayberry processing.

Engineered fungus containing a caterpillar gene kills insects rapidly by disrupting their ecto- and endo-microbiomes

Similar to the physiological importance of gut microbiomes, recent works have shown that insect ectomicrobiotas can mediate defensive colonization resistance against fungal parasites that infect via cuticle penetration. Here we show that engineering the entomopathogenic fungus Metarhizium robertsii with a potent antibacterial moricin gene from silkworms substantially enhances the ability of the fungus to kill mosquitos, locusts, and two Drosophila species. Further use of Drosophila melanogaster as an infection model, quantitative microbiome analysis reveals that engineered strains designed to suppress insect cuticular bacteria additionally disrupt gut microbiomes. An overgrowth of harmful bacteria such as the opportunistic pathogens of Providencia species is detected that can accelerate insect death. In support, quantitative analysis of antimicrobial genes in fly fat bodies and guts indicates that topical fungal infections result in the compromise of intestinal immune responses. In addition to providing an innovative strategy for improving the potency of mycoinsecticides, our data solidify the importance of both the ecto- and endo-microbiomes in maintaining insect wellbeing.

Glycine rich proteins of ticks: more than a cement component

Glycine-rich proteins (GRPs) are arbitrarily defined as those containing 20% or more glycine residues and constitute a superfamily divided into subfamilies based on their structure and/or function. GRPs have been identified in a diverse array of organisms and have been shown to possess a number of distinctive biological characteristics, including nucleic acid binding, adhesive glue-like properties, antimicrobial activity, involvement in the stress response and in the formation of cuticle components. In ticks, their expression has been described and studied mainly in the salivary glands, and their primary function is usually associated with cement formation and/or structure. Conversely, several GRPs are present in all tick developmental stages, and the expression of many GRP genes is modulated by physiological processes and immune challenges, such as feeding and pathogen infection. Considering that some tick GRPs appear to play essential roles in the tick life cycle, they have been evaluated as immune targets, with a focus on their potential application in vaccine development. This review highlights the roles that tick GRPs may perform beyond the formation and maintenance of the cement scaffold, including structural characterization, locations and functional relevance, hypothetical functions, and their potential use in anti-tick vaccine development.

Relish involved in immunity and larval survival in the willow leaf beetle Plagiodera versicolora

BACKGROUND

Insects mainly rely on innate immunity against pathogen infection. Plagiodera versicolora (Coleoptera: Chrysomelidae), is a worldwide leaf-eating forest pest in salicaceous trees. However, the mechanisms behind the immunodeficiency pathway (IMD) remain poorly understood.

RESULTS

In this study, we obtained a Relish gene from transcriptome analysis. Tissue and instar expression profiles were subsequently obtained using quantitative real-time polymerase chain reaction analysis. The results showed that Relish has high expression levels in eggs, larvae and adults, and especially in fat bodies. Transcripts of the tested antimicrobial peptides (AMPs), defensin1, defensin2 and attacin2 were downregulated by dsRelish. Knockdown of Relish led to greater mortality in larvae after Staphylococcus aureus infection. In addition, we performed bacterial 16S ribosomal RNA-based high-throughput sequencing. The results showed that the relative abundance of some gut bacteria was significantly altered after dsRelish ingestion.

CONCLUSION

This study provides a greater understanding of the IMD signaling pathway, facilitating functional studies of Relish in P. versicolora. Moreover, a genetic pest management technique might be developed using Relish as a lethal gene to control the pest P. versicolora. © 2024 Society of Chemical Industry.

Exploring oak processionary caterpillar induced lepidopterism (Part 1): unveiling molecular insights through transcriptomics and proteomics

Lepidopterism, a skin inflammation condition caused by direct or airborne exposure to irritating hairs (setae) from processionary caterpillars, is becoming a significant public health concern. Recent outbreaks of the oak processionary caterpillar (Thaumetopoea processionea) have caused noteworthy health and economic consequences, with a rising frequency expected in the future, exacerbated by global warming promoting the survival of the caterpillar. Current medical treatments focus on symptom relief due to the lack of an effective therapy. While the source is known, understanding the precise causes of symptoms remain incomplete understood. In this study, we employed an advanced method to extract venom from the setae and identify the venom components through high-quality de novo transcriptomics, venom proteomics, and bioinformatic analysis. A total of 171 venom components were identified, including allergens, odorant binding proteins, small peptides, enzymes, enzyme inhibitors, and chitin biosynthesis products, potentially responsible for inflammatory and allergic reactions. This work presents the first comprehensive proteotranscriptomic database of T. processionea, contributing to understanding the complexity of lepidopterism. Furthermore, these findings hold promise for advancing therapeutic approaches to mitigate the global health impact of T. processionea and related caterpillars.

Human Defensin 5 Inhibits Plasmodium yoelii Development in Anopheles stephensi by Promoting Innate Immune Response

Malaria poses a serious threat to human health. Existing vector-based interventions have shortcomings, such as environmental pollution, strong resistance to chemical insecticides, and the slow effects of biological insecticides. Therefore, the need to develop novel strategies for controlling malaria, such as reducing mosquito vector competence, is escalating. Human defensin 5 (HD5) has broad-spectrum antimicrobial activity. To determine its effect on Plasmodium development in mosquitoes, HD5 was injected into Anopheles stephensi at various time points. The infection density of Plasmodium yoelii in An. stephensi was substantially reduced by HD5 treatment administered 24 h prior to infection or 6, 12, or 24 h post-infection (hpi). We found that HD5 treatment upregulated the expression of the innate immune effectors TEP1, MyD88, and Rel1 at 24 and 72 hpi. Furthermore, the RNA interference of MyD88, a key upstream molecule in the Toll signaling pathway, decreased the HD5-induced resistance of mosquitoes against Plasmodium infection. These results suggest that HD5 microinjection inhibits the development of malaria parasites in An. stephensi by activating the Toll signaling pathway.

High amphipathicity of α-helical peptides enhances unmethylated CpG DNA-induced activation of mouse macrophage-like RAW264.7 cells

The α-helical antimicrobial peptide Kn2-7 enhances the activation of mouse macrophage-like RAW264.7 induced by DNA containing unmethylated cytosine-guanine motifs (CpG DNA). This enhancement is related to increased cellular uptake of DNA by Kn2-7, but the relevant properties of Kn2-7 are unknown. Physicochemical property analysis revealed that Kn2-7 has high amphipathicity. In contrast, the α-helical antimicrobial peptide L5, which increases the cellular uptake of CpG DNA but does not enhance CpG DNA-induced activation, has low amphipathicity. Kn2-7 derivatives with decreased amphipathicity but the same amino acid composition as Kn2-7 did not enhance CpG DNA-induced activation. On the other hand, L5 derivatives with high amphipathicity but the same amino acid composition as L5 enhanced CpG DNA-induced activation. Cellular uptake of DNA was not increased by the L5 derivatives, indicating that high amphipathicity does not affect DNA uptake. Furthermore, α-helical peptides with reversed sequences relative to the Kn2-7 and L5 derivatives with high amphipathicity were synthesized. The reversed-sequence peptides, which had the same amphipathicity but different amino acid sequences from their counterparts, enhanced CpG DNA-induced activation. Taken together, these observations indicate that the high amphipathicity of α-helical peptides enhances the CpG DNA-induced activation of RAW264.7.

Antimalarial activity of cecropin antimicrobial peptides derived from Anopheles mosquitoes

The emergence of clinically drug-resistant malaria parasites requires the urgent development of new drugs. Mosquitoes are vectors of multiple pathogens and have developed resistance mechanisms against them, which often involve antimicrobial peptides (AMPs). An-cecB is an AMP of the malaria-transmitting mosquito genus Anopheles, and we herein report its antimalarial activity against Plasmodium falciparum 3D7, the artemisinin-resistant strain 803, and the chloroquine-resistant strain Dd2 in vitro. We also demonstrate its anti-parasite activity in vivo, using the rodent malaria parasite Plasmodium berghei (ANKA). We show that An-cecB displays potent antimalarial activity and that its mechanism of action may occur through direct killing of the parasite or through interaction with infected red blood cell membranes. Unfortunately, An-cecB was found to be cytotoxic to mammalian cells and had poor antimalarial activity in vivo. However, its truncated peptide An-cecB-1 retained most of its antimalarial activity and avoided its cytotoxicity in vitro. An-cecB-1 also showed better antimalarial activity in vivo. Mosquito-derived AMPs may provide new ideas for the development of antimalarial drugs against drug-resistant parasites, and An-cecB has potential use as a template for antimalarial peptides.

Antibiotics suppress the expression of antimicrobial peptides and increase sensitivity of Cydia pomonella to granulosis virus

Cydia pomonella granulovirus (CpGV) is a highly specific and environmentally friendly pathogenic virus successfully used as a biological insecticide against codling moth larvae. Continuous application of CpGV has led to high levels of resistance in codling moth, Cydia pomonella (C. pomonella). Nevertheless, the specific molecular mechanisms underlying the development of resistance in codling moths to CpGV have been rarely investigated. This study explored the potential antiviral immune roles of codling moth antimicrobial peptides (AMPs) against CpGV. A total of 11 AMP genes classified in cecropin, defensin, gloverin, and attacin subfamilies, were identified in the codling moth genome. The cecropin and gloverin subfamilies were found to be the ancestral genes of the AMP gene family. The expression of two AMP genes (CmGlo1 and CmAtt1) significantly increased following CpGV challenge, and CmGlo1 and CmAtt1 gene silencing resulted in a significant increase in CpGV replication in codling moth larvae. The hemolymph and fat body serve as major viral immune functional tissues in codling moth larvae. Moreover, zhongshengmycin significantly reduced the diversity and abundance of codling moth larvae gut microbiota, thereby suppressing the expression of CmAtt1 AMP gene. We also found that the combination of the virus with zhongshengmycin would enhance the insecticidal effects of CpGV. This study provides the first explanation of the molecular mechanisms driving CpGV immune function development in codling moths, approached from the perspective of the codling moth itself. Additionally, we introduced an alternative approach to combat codling moth in the field by combining antibiotics with biopesticides to amplify the insecticidal effects of the latter.

Effects of four types of natural bait on water quality, feeding, growth, and antioxidant enzyme activity of Monopterus albus in a recirculating aquaculture system

Monopterus albus is one of China's renowned and superior aquaculture species, with its seedlings mainly sourced from wild capture. One of the bottlenecks in M. albus aquaculture is the high mortality rate and low feeding initiation rate from stocking wild fry to the initiation of feeding. In production, trash fish is commonly used to wean M. albus juveniles onto feeding. In this study, we introduced three other natural feeds, earthworms (EW), yellow mealworms (YMW), and fly maggots (FM), with frozen trash fish (TF) serving as the control group, to evaluate the effects of these four natural feeds on the survival rate, feeding initiation, antioxidant enzymes activity, and body composition of M. albus juveniles under recirculating water aquaculture conditions. The experiment comprised four treatments, each with three replicates. Each replicate consisted of stocking 150 M. albus juveniles weighing 10.02 ± 0.89 g in size, raised for 5 weeks. The survival rate of the YMW group was 73.33%-85.33%, which was significantly higher than that of the other three bait groups (p < 0.05). The four bait groups showed no significant differences in final body weight and specific growth rate (SGR) (p > 0.05). The EW group showed the highest final body weight, with an average SGR of 2.73, whereas the YMW group had an average SGR of 1.87. The average daily feeding amount was significantly higher in EW and YMW groups than in the other two groups (p < 0.05). The percentage of feeding amount to fish weight in the EW group reached 7.3% in the fifth week. After 5 weeks of cultivation, NO2 --N content was significantly higher in the waters of the TF and EW groups than in the waters of the FM and YMW groups (p < 0.05), there was no significant difference in TAN content among the treatment groups (p > 0.05). Liver malondialdehyde content was significantly higher in the TF group than in the other bait groups (p < 0.05). GSH-Px activity was significantly higher in the EW group than in the FM group and YMW group. No significant differences in SOD and CAT activity and T-AOC were observed among the bait groups (p > 0.05). The increase in crude protein content was significantly higher in the TF group than in the FM group, but the increase in crude ash content was significantly lower in the TFgroup. In conclusion, Tenebrio molitor could potentially serve as one of the alternative feeds during the initial stages of M. albus juveniles stocking.

Peptides with Antimicrobial Activity in the Saliva of the Malaria Vector Anopheles coluzzii

Mosquito saliva plays a crucial physiological role in both sugar and blood feeding by helping sugar digestion and exerting antihemostatic functions. During meal acquisition, mosquitoes are exposed to the internalization of external microbes. Since mosquitoes reingest significant amounts of saliva during feeding, we hypothesized that salivary antimicrobial components may participate in the protection of mouthparts, the crop, and the gut by inhibiting bacterial growth. To identify novel potential antimicrobials from mosquito saliva, we selected 11 candidates from Anopheles coluzzii salivary transcriptomic datasets and obtained them either using a cell-free transcription/translation expression system or, when feasible, via chemical synthesis. Hyp6.2 and hyp13, which were predicted to be produced as propeptides and cleaved in shorter mature forms, showed the most interesting results in bacterial growth inhibition assays. Hyp6.2 (putative mature form, 35 amino acid residues) significantly inhibited the growth of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli and Serratia marcescens) bacteria. Hyp13 (short form, 19 amino acid residues) dose-dependently inhibited E. coli and S. marcescens growth, inducing membrane disruption in both Gram-positive and Gram-negative bacteria as indicated with scanning electron microscopy. In conclusion, we identified two A. coluzzii salivary peptides inhibiting Gram-positive and Gram-negative bacteria growth and possibly contributing to the protection of mosquito mouthparts and digestive tracts from microbial infection during and/or after feeding.

The ncRNA-mediated regulatory networks of defensins and lysozymes in Riptortus pedestris: involvement in response to gut bacterial disturbances

Insects depend on humoral immunity against intruders through the secretion of antimicrobial peptides (AMPs) and immune effectors via NF-κB transcription factors, and their fitness is improved by gut bacterial microbiota. Although there are growing numbers of reports on noncoding RNAs (ncRNAs) involving in immune responses against pathogens, comprehensive studies of ncRNA-AMP regulatory networks in Riptortus pedestris, which is one of the widely distributed pests in East Asia, are still not well understood under feeding environmental changes. The objective of this study employed the whole-transcriptome sequencing (WTS) to systematically identify the lncRNAs (long noncoding RNA) and circRNAs (circular RNA) and to obtain their differential expression from the R. pedestris gut under different feeding conditions. Functional annotation indicated that they were mainly enriched in various biological processes with the GO and KEGG databases, especially in immune signaling pathways. Five defensin (four novel members) and eleven lysozyme (nine novel members) family genes were identified and characterized from WTS data, and meanwhile, phylogenetic analysis confirmed their classification. Subsequently, the miRNA-mRNA interaction network of above two AMPs and lncRNA-involved ceRNA (competing endogenous RNA) regulatory network of one lysozyme were predicted and built based on bioinformatic prediction and calculation, and the expression patterns of differentially expressed (DE) defensins, and DE lysozymes and related DE ncRNAs were estimated and selected among all the comparison groups. Finally, to integrate the analyses of WTS and previous 16S rRNA amplicon sequencing, we conducted the Pearson correlation analysis to reveal the significantly positive or negative correlation between above DE AMPs and ncRNAs, as well as most changes in the gut bacterial microbiota at the genus level of R. pedestris. Taken together, the present observations provide great insights into the ncRNA regulatory networks of AMPs in response to rearing environmental changes in insects and uncover new potential strategies for pest control in the future.

The Function of Termicin from Odontotermes formosanus (Shiraki) in the Defense against Bacillus thuringiensis (Bt) and Beauveria bassiana (Bb) Infection

Odontotermes formosanus (Shiraki) is a subterranean termite species known for causing severe damage to trees and structures such as dams. During the synergistic evolution of O. formosanus with pathogenic bacteria, the termite has developed a robust innate immunity. Termicin is a crucial antimicrobial peptide in termites, significantly contributing to the defense against external infections. Building upon the successful construction and expression of the dsRNA-HT115 engineering strains of dsOftermicin1 and dsOftermicin2 in our laboratory, this work employs the ultrasonic breaking method to establish an inactivated dsOftermicins-HT115 technological system capable of producing a substantial quantity of dsRNA. This approach also addresses the limitation of transgenic strains which cannot be directly applied. Treatment of O. formosanus with dsOftermicins produced by this method could enhance the virulence of both Bt and Bb to the termites. This study laid the theoretical groundwork for the development of novel termite immunosuppressants and for the advancement and application of termite biological control strategies.

Innate immunity in Aedes mosquitoes: from pathogen resistance to shaping the microbiota

Discussions of host-microbe interactions in mosquito vectors are frequently dominated by a focus on the human pathogens they transmit (e.g. Plasmodium parasites and arboviruses). Underlying the interactions between a vector and its transmissible pathogens, however, is the physiology of an insect living and interacting with a world of bacteria and fungi including commensals, mutualists and primary and opportunistic pathogens. Here we review what is known about the bacteria and fungi associated with mosquitoes, with an emphasis on the members of the Aedes genus. We explore the reciprocal effects of microbe on mosquito, and mosquito on microbe. We analyse the roles of bacterial and fungal symbionts in mosquito development, their effects on vector competence, and their potential uses as biocontrol agents and vectors for paratransgenesis. We explore the compartments of the mosquito gut, uncovering the regionalization of immune effectors and modulators, which create the zones of resistance and immune tolerance with which the mosquito host controls and corrals its microbial symbionts. We examine the anatomical patterning of basally expressed antimicrobial peptides. Finally, we review the relationships between inducible antimicrobial peptides and canonical immune signalling pathways, comparing and contrasting current knowledge on each pathway in mosquitoes to the model insect Drosophila melanogaster. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Antimicrobial Peptides towards Clinical Application-A Long History to Be Concluded

Antimicrobial peptides (AMPs) are molecules with an amphipathic structure that enables them to interact with bacterial membranes. This interaction can lead to membrane crossing and disruption with pore formation, culminating in cell death. They are produced naturally in various organisms, including humans, animals, plants and microorganisms. In higher animals, they are part of the innate immune system, where they counteract infection by bacteria, fungi, viruses and parasites. AMPs can also be designed de novo by bioinformatic approaches or selected from combinatorial libraries, and then produced by chemical or recombinant procedures. Since their discovery, AMPs have aroused interest as potential antibiotics, although few have reached the market due to stability limits or toxicity. Here, we describe the development phase and a number of clinical trials of antimicrobial peptides. We also provide an update on AMPs in the pharmaceutical industry and an overall view of their therapeutic market. Modifications to peptide structures to improve stability in vivo and bioavailability are also described.

Insect Antimicrobial Peptides as Guardians of Immunity and Beyond: A Review

Antimicrobial peptides (AMPs), as immune effectors synthesized by a variety of organisms, not only constitute a robust defense mechanism against a broad spectrum of pathogens in the host but also show promising applications as effective antimicrobial agents. Notably, insects are significant reservoirs of natural AMPs. However, the complex array of variations in types, quantities, antimicrobial activities, and production pathways of AMPs, as well as evolution of AMPs across insect species, presents a significant challenge for immunity system understanding and AMP applications. This review covers insect AMP discoveries, classification, common properties, and mechanisms of action. Additionally, the types, quantities, and activities of immune-related AMPs in each model insect are also summarized. We conducted the first comprehensive investigation into the diversity, distribution, and evolution of 20 types of AMPs in model insects, employing phylogenetic analysis to describe their evolutionary relationships and shed light on conserved and distinctive AMP families. Furthermore, we summarize the regulatory pathways of AMP production through classical signaling pathways and additional pathways associated with Nitric Oxide, insulin-like signaling, and hormones. This review advances our understanding of AMPs as guardians in insect immunity systems and unlocks a gateway to insect AMP resources, facilitating the use of AMPs to address food safety concerns.

A single amino acid polymorphism in natural Metchnikowin alleles of Drosophila results in systemic immunity and life history tradeoffs

Antimicrobial peptides (AMPs) are at the interface of interactions between hosts and microbes and are therefore expected to be rapidly evolving in a coevolutionary arms race with pathogens. In contrast, previous work demonstrated that insect AMPs tend to evolve more slowly than the genome average. Metchikowin (Mtk) is a Drosophila AMP that has a single amino acid residue that segregates as either proline (P) or arginine (R) in populations of four different species, some of which diverged more than 10 million years ago. These results suggest that there is a distinct functional importance to each allele. The most likely hypotheses are driven by two main questions: does each allele have a different efficacy against different specific pathogens (specificity hypothesis)? Or, is one allele a more potent antimicrobial, but with a host fitness cost (autoimmune hypothesis)? To assess their functional differences, we created D. melanogaster lines with the P allele, R allele, or Mtk null mutation using CRISPR/Cas9 genome editing and performed a series of life history and infection assays to assess them. In males, testing of systemic immune responses to a repertoire of bacteria and fungi demonstrated that the R allele performs as well or better than the P and null alleles with most infections. Females show some results that contrast with males, with Mtk alleles either not contributing to survival or with the P allele outperforming the R allele. In addition, measurements of life history traits demonstrate that the R allele is more costly in the absence of infection for both sexes. These results are consistent with both the specificity hypothesis (either allele can perform better against certain pathogens depending on context), and the autoimmune hypothesis (the R allele is generally the more potent antimicrobial in males, and carries a fitness cost). These results provide strong in vivo evidence that differential fitness with or without infection and sex-based functional differences in alleles may be adaptive mechanisms of maintaining immune gene polymorphisms in contrast with expectations of rapid evolution. Therefore, a complex interplay of forces including pathogen species and host sex may lead to balancing selection for immune genotypes. Strikingly, this selection may act on even a single amino acid polymorphism in an AMP.

Oxidative stress governs mosquito innate immune signalling to reduce chikungunya virus infection in Aedes-derived cells

Arboviruses such as chikungunya, dengue and zika viruses cause debilitating diseases in humans. The principal vector species that transmits these viruses is the Aedes mosquito. Lack of substantial knowledge of the vector species hinders the advancement of strategies for controlling the spread of arboviruses. To supplement our information on mosquitoes' responses to virus infection, we utilized Aedes aegypti-derived Aag2 cells to study changes at the transcriptional level during infection with chikungunya virus (CHIKV). We observed that genes belonging to the redox pathway were significantly differentially regulated. Upon quantifying reactive oxygen species (ROS) in the cells during viral infection, we further discovered that ROS levels are considerably higher during the early hours of infection; however, as the infection progresses, an increase in antioxidant gene expression suppresses the oxidative stress in cells. Our study also suggests that ROS is a critical regulator of viral replication in cells and inhibits intracellular and extracellular viral replication by promoting the Rel2-mediated Imd immune signalling pathway. In conclusion, our study provides evidence for a regulatory role of oxidative stress in infected Aedes-derived cells.

Identification of Genes Associated with Resistance to Persulcatusin, a Tick Defensin from Ixodes persulcatus

Antimicrobial peptides (AMPs) are present in a wide range of plants, animals, and microorganisms. Since AMPs are characterized by their effectiveness against emergent antibiotic-resistant bacteria, they are attracting attention as next-generation antimicrobial compounds that could solve the problem of drug-resistant bacteria. Persulcatusin (IP), an antibacterial peptide derived from the hard tick Ixodes persulcatus, shows high antibacterial activity against various Gram- positive bacteria as well as multidrug-resistant bacteria. However, reports on the antibacterial action and resistance mechanisms of IP are scarce. In this study, we spontaneously generated mutants showing increased a minimum inhibitory concentration (MIC) of IP and analyzed their cross-resistance to other AMPs and antibiotics. We also used fluorescent probes to investigate the target of IP activity by evaluating IP-induced damage to the bacterial cytoplasmic membrane. Our findings suggest that the antimicrobial activity of IP on bacterial cytoplasmic membranes occurs via a mechanism of action different from that of known AMPs. Furthermore, we screened for mutants with high susceptibility to IP using a transposon mutant library and identified 16 genes involved in IP resistance. Our results indicate that IP, like other AMPs, depolarizes the bacterial cytoplasmic membrane, but it may also alter membrane structure and inhibit cell-wall synthesis.

Dietary and Therapeutic Benefits of Edible Insects: A Global Perspective

Edible insects are gaining traction worldwide for research and development. This review synthesizes a large and well-established body of research literature on the high nutritional value and variety of pharmacological properties of edible insects. Positive benefits of insect-derived products include immune enhancement; gastrointestinal protection; antitumor, antioxidant, and anti-inflammatory capacities; antibacterial activities; blood lipid and glucose regulation; lowering of blood pressure; and decreased risk of cardiovascular diseases. However, the pharmacological mechanisms of these active components of edible insects in humans have received limited research attention. In addition, we discuss health risks (safety); application prospects; regulations and policies governing their production and consumption with a view to promote innovations, intraglobal trade, and economic development; and suggestions for future directions for further pharmacological functional studies. The aim is to review the current state of knowledge and research trends on edible insects as functional ingredients beneficial to the nutrition and health of humans and animals (livestock, aquatic species, and pets).

Alternative and Sustainable Protein Sources in Pig Diet: A Review

The search for alternative protein sources to soybean meal (SBM) in animal feeding is a strategic objective to reduce production costs and contribute to sustainable animal production. Spirulina, due to the high protein content, has emerged as a potential cost-effective, sustainable, viable, and high-nutritional-value food resource for many animal species. Insect larvae (Tenebrio molitor and Hermetia illucens) are also considered potential alternatives to SBM, given their high edible percentage of almost 100%, as well as a protein value higher than that of vegetable proteins. Rapeseed meal and grain legumes, such as fava beans, peas, lupins, and chickpea, can also be used as locally producible protein ingredients. This study reviews the nutritional value of these potential alternatives to SBM in pig diets, and their effects on animal performance, digestion, immune system, and the physicochemical and sensorial characteristics of meat, including processed pork products. The limits on their use in pig feeding are also reviewed to indicate gaps to be filled in future research on the supplementation level of these potential alternative protein sources in pig diets.

Rhynchophorus ferrugineus larvae: A novel source for combating broad-spectrum bacterial and fungal infections

Antimicrobial resistance is a growing concern due to the growth of antibiotic-resistant microorganisms, which makes it difficult to treat infection. Due to its broad-spectrum antimicrobial properties against a diverse array of bacteria, both Gram-positive and Gram-negative bacteria, and fungi, Rhynchophorus ferrugineus larval antimicrobial peptides (AMPs) have demonstrated potential as antimicrobial agents for the treatment of microbial infections and prevention of antibiotic resistance. This study emphasizes the unexplored mechanisms of action of R. ferrugineus larvae against microorganisms. Among the most widely discussed mechanisms is the effect of AMPs in larvae in response to a threat or infection. Modulation of immune-related genes in the intestine and phagocytic capacity of its hemocytes may also affect the antimicrobial activity of R. ferrugineus larvae, with an increase in phenoloxidase activity possibly correlated with microbial clearance and survival rates of larvae. The safety and toxicity of R. ferrugineus larvae extracts, as well as their long-term efficacy, are also addressed in this paper. The implications of future research are explored in this paper, and it is certain that R. ferrugineus larvae have the potential to be developed as a broad-spectrum antimicrobial agent with proper investigation.

Transcriptomic responses to location learning by honeybee dancers are partly mirrored in the brains of dance-followers

The waggle dances of honeybees are a strikingly complex form of animal communication that underlie the collective foraging behaviour of colonies. The mechanisms by which bees assess the locations of forage sites that they have visited for representation on the dancefloor are now well-understood, but few studies have considered the remarkable backward translation of such information into flight vectors by dance-followers. Here, we explore whether the gene expression patterns that are induced through individual learning about foraging locations are mirrored when bees learn about those same locations from their nest-mates. We first confirmed that the mushroom bodies of honeybee dancers show a specific transcriptomic response to learning about distance, and then showed that approximately 5% of those genes were also differentially expressed by bees that follow dances for the same foraging sites, but had never visited them. A subset of these genes were also differentially expressed when we manipulated distance perception through an optic flow paradigm, and responses to learning about target direction were also in part mirrored in the brains of dance followers. Our findings show a molecular footprint of the transfer of learnt information from one animal to another through this extraordinary communication system, highlighting the dynamic role of the genome in mediating even very short-term behavioural changes.