Profiling the venom gland transcriptome of Tetramorium bicarinatum (Hymenoptera: Formicidae): The first transcriptome analysis of an ant species

Transcriptomic and biochemical analysis from the venom gland of the neotropical ant Odontomachus chelifer

The genus Odontomachus is widely distributed in neotropical areas throughout Central and South America. It is a stinging ant that subdues its prey (insects) by injecting them a cocktail of toxic molecules (venom). Ant venoms are generally composed of formic acid, alkaloids, hydrocarbons, amines, peptides, and proteins. Odontomachus chelifer is an ant that inhabits neotropical regions from Mexico to Argentina. Unlike the venom of other animals such as scorpions, spiders and snakes, this ant venom has seldom been analyzed comprehensively, and their compositions are not yet completely known. In the present study, we performed a partial investigation of enzymatic and functional activities of O. chelifer ant venom, and we provide a global insight on the transcripts expressed in the venom gland to better understand their properties. The crude venom showed phospholipase A₂ and antiparasitic activities. RNA sequencing (Illumina platform) of the venom gland of O. chelifer generated 61, 422, 898 reads and de novo assembly Trinity generated 50,220 contigs. BUSCO analysis against Arthropoda_db10 showed that 92.89% of the BUSCO groups have complete gene representation (single-copy or duplicated), while 4.05% are only partially recovered, and 3.06% are missing. The 30 most expressed genes in O. chelifer venom gland transcriptome included important transcripts involved in venom function such as U-poneritoxin (01)-Om1a-like (pilosulin), chitinase 2, venom allergen 3, chymotrypsin 1 and 2 and glutathione S-transferase. Analysis of the molecular function revealed that the largest number of transcripts were related to catalytic activity, including phospholipases. These data emphasize the potential of O. chelifer venom for prospection of molecules with biotechnological application.

A combined protein toxin screening based on the transcriptome and proteome of Solenopsis invicta

Background

Multi-omics technology provides a good tool to analyze the protein toxin composition and search for the potential pathogenic factors of Solenopsis invicta, under the great harm of the accelerated invasion in southern China.

Methods

Species collection, functional annotation, toxin screening, and 3D modeling construction of three interested toxins were performed based on the successfully constructed transcriptome and proteome of S. invicta.

Results

A total of 33,231 unigenes and 721 proteins were obtained from the constructed transcriptome and proteome, of which 9,842 (29.62%) and 4,844 (14.58%) unigenes, as well as 469 (65.05%) and 71 (99.45%) proteins were annotated against the databases of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, respectively. After comparing with the uniprot toxin database, a total of 316 unigenes and 47 proteins (calglandulin, venom allergen 3, and venom prothrombin activator hopsarin-D, etc.) were successfully screened.

Conclusions

The update of annotations at the transcriptome and proteome levels presents a progression in the comprehension of S. invicta in China. We also provide a protein toxin list that could be used for further exploration of toxicity as well as its antagonistic strategy by S. invicta.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12953-022-00197-z.

Profiling hymenopteran venom toxins: Protein families, structural landscape, biological activities, and pharmacological benefits

Hymenopterans are an untapped source of venom secretions. Their recent proteo-transcriptomic studies have revealed an extraordinary pool of toxins that participate in various biological processes, including pain, paralysis, allergic reactions, and antimicrobial activities. Comprehensive and clade-specific campaigns to collect hymenopteran venoms are therefore needed. We consider that data-driven bioprospecting may help prioritise sampling and alleviate associated costs. This work established the current protein landscape from hymenopteran venoms to evaluate possible sample bias by studying their origins, sequence diversity, known structures, and biological functions. We collected all 282 reported hymenopteran toxins (peptides and proteins) from the UniProt database that we clustered into 21 protein families from the three studied clades - wasps, bees, and ants. We identified 119 biological targets of hymenopteran toxins ranging from pathogen membranes to eukaryotic proteases, ion channels and protein receptors. Our systematic study further extended to hymenopteran toxins' therapeutic and biotechnological values, where we revealed promising applications in crop pests, human infections, autoimmune diseases, and neurodegenerative disorders.

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The hymenopteran toxin diversity includes 21 protein families from 81 species.

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Some toxins are shared across wasps, bees and ants, others are clade-specific.

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Their venoms contain membrane-active peptides, neurotoxins, allergens and enzymes.

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Hymenopteran toxins have been tested against a total of 119 biological targets.

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Hymenopteran toxins were predominantly evaluated as anti-infective agents.

Venom profile of the European carpenter bee Xylocopa violacea: Evolutionary and applied considerations on its toxin components

Modern venomics is increasing its focus on hymenopterans such as honeybees, bumblebees, parasitoid wasps, ants and true wasps. However solitary bees remain understudied in comparison and the few available venom studies focus on short melittin-like sequences and antimicrobial peptides. Herein we describe the first comprehensive venom profile of a solitary bee, the violet carpenter bee Xylocopa violacea, by using proteo-transcriptomics. We reveal a diverse and complex venom profile with 43 different protein families identified from dissected venom gland extracts of which 32 are also detected in the defensively injected venom. Melittin and apamin are the most highly secreted components, followed by Phospholipase A2, Icarapin, Secapin and three novel components. Other components, including eight novel protein families, are rather lowly expressed. We further identify multiple forms of apamin-like peptides. The melittin-like sequences of solitary bees separate into two clades, one comprised most sequences from solitary bees including xylopin (the variant in Xylocopa), while sequences from Lasioglossa appear closer related to melittin-like peptides from Bombus (Bombolittins). Our study suggests that more proteo-transcriptomic data from other solitary bees should be complemented with corresponding genome data to fully understand the evolution and complexity of bee venom proteins, and is of a particular need to disentangle the ambiguous phylogenetic relations of short peptides.

Systematic and computational identification of Androctonus crassicauda long non-coding RNAs

The potential function of long non-coding RNAs in regulating neighbor protein-coding genes has attracted scientists' attention. Despite the important role of lncRNAs in biological processes, a limited number of studies focus on non-model animal lncRNAs. In this study, we used a stringent step-by-step filtering pipeline and machine learning-based tools to identify the specific Androctonus crassicauda lncRNAs and analyze the features of predicted scorpion lncRNAs. 13,401 lncRNAs were detected using pipeline in A. crassicauda transcriptome. The blast results indicated that the majority of these lncRNAs sequences (12,642) have no identifiable orthologs even in closely related species and those considered as novel lncRNAs. Compared to lncRNA prediction tools indicated that our pipeline is a helpful approach to distinguish protein-coding and non-coding transcripts from RNA sequencing data of species without reference genomes. Moreover, analyzing lncRNA characteristics in A. crassicauda uncovered that lower protein-coding potential, lower GC content, shorter transcript length, and less number of isoform per gene are outstanding features of A. crassicauda lncRNAs transcripts.

Proteomic-components provide insights into the defensive secretion in termite workers of the soldierless genus Ruptitermes

Termite soldiers constitute the defensive frontline of the colonies, despite workers also perform such tasks, especially within the Neotropical Apicotermitinae, in which all species are soldierless. Workers of the genus Ruptitermes display an extreme form of defense, characterized by body rupture and release of a sticky secretion. Previous observations suggested that such behavior may be advantageous against enemies, but the chemical composition of this secretion has been neglected. Here we firstly provide the proteomic profile of the defensive secretion of Ruptitermes reconditus and Ruptitermes pitan workers. Additionally, the mechanisms of action of this behavior was evaluated through different bioassays. A total of 446 proteins were identified in R. reconditus and 391 proteins in R. pitan, which were classified into: toxins, defensins and proteolytic enzymes; sticky components/ alarm communication; proteins related to detoxification processes; proteins involved in folding/conformation and post-translational modifications; housekeeping proteins; and uncharacterized/hypothetical proteins. According to the bioassays, the self-sacrifice is triggered by a physical stimulus, and the defensive secretion may cause immobility and death of the opponents. Assuming that termites are abundant in the tropics and therefore exposed to predators, suicidal behaviors seem to be advantageous, since the loss of an individual benefit the whole colony. SIGNIFICANCE: Although recent studies have reported the biochemical composition of different weapons in soldiered species of termites, such efforts had not been applied to sordierless taxa up until now. Thus, this is the first report of the defensive mechanisms in soldierless termite species based on proteomic analysis. The diversity of compounds, which included toxin-like and mucin-like proteins, reflect the mechanisms of action of the defensive secretion released by termite workers, which may cause immobility and death of the opponents. Our findings may contribute to the knowledge regarding the development of defensive strategies in termites, especially in groups which lost the soldier caste during the evolution.

Thymoquinone ameliorates Pachycondyla sennaarensis venom-induced acute toxic shock in male rats

BACKGROUND

For many decades, the sting of Samsun ant (Pachycondyla sennaarensis) has been a serious clinical challenge for the people living in some of the major Middle East and Asian countries. In the present study, the therapeutic potential of Nigella sativa derived plant extract component, thymoquinone (TQ) has been tested against the Samsun ant venom (SAV) at the toxic dose in the rats.

METHODS

The adult male rats were divided into four groups (n = 10): control, SAV treated, SAV + TQ treated and TQ alone treated. It was found that the sub-lethal dose of SAV alters not only many of the kidney and liver function markers but also induces oxidative stress in the animals. Moreover, the SAV also disturbs various immunological parameters including expression of PMNs, CD-80, CD-86, interleukins and other cytokines compromising the affected organism towards mild to severe allergic reactions including life-risking anaphylaxis.

RESULTS

The plant extract, TQ, effectively restores many of the biochemical and oxidative stress parameters comparable to the normal concomitant with improving the immunological aspects that might attributive in relieving from SAV-induced toxicity and allergic reactions in the affected organism to a greater extent.

CONCLUSION

Hence, TQ has an excellent antidote property against SAV-induced toxicities in vivo. Although the study is a vivid indication of the potential therapeutic potential of TQ against the SAV induced in vivo toxicity, yet the actual mechanism of interaction translating the toxicity amelioration warrants further investigations.

Samsum ant venom modulates the immune response and redox status at the acute toxic dose in vivo

BACKGROUND

Ant venoms express surface molecules that participate in antigen presentation involving pro- and anti-inflammatory cytokines. This work aims to investigate the expression of MHC-II, CD80 and CD86 on the polymorphonuclear cells (PMNs) in rats injected with samsum ant venom (SAV).

METHODS

Rats were divided into three groups - control, SAV-treated (intraperitoneal route, 600 μg/kg), and SAV-treated (subcutaneous route, 600 μg/kg). After five doses, animals were euthanized and samples collected for analysis.

RESULTS

The subcutaneous SAV-trated rats presented decreased levels of glutathione with increased cholesterol and triglyceride levels. Intraperitoneal SAV-treated animals displayed significantly reduced concentrations of both IFN-γ and IL-17 in comparison with the control group. However, intraperitoneal and subcutaneous SAV-treated rats were able to upregulate the expressions of MHC-II, CD80 and CD86 on PMNs in comparison with the control respectively. The histological examination showed severe lymphocyte depletion in the splenic white pulp of the intraperitoneal SAV-injected rats.

CONCLUSION

Stimulation of PMNs by SAV leads to upregulation of MHC-II, CD 80, and CD 86, which plays critical roles in antigen presentation and consequently proliferation of T-cells. Subcutaneous route was more efficient than intraperitoneal by elevating MHC-II, CD80 and CD86 expression, disturbing oxidative stability and increasing lipogram concentration.

Identification and Functional Characterization of a Novel Insecticidal Decapeptide from the Myrmicine Ant Manica rubida

Ant venoms contain many small, linear peptides, an untapped source of bioactive peptide toxins. The control of agricultural insect pests currently depends primarily on chemical insecticides, but their intensive use damages the environment and human health, and encourages the emergence of resistant pest populations. This has promoted interest in animal venoms as a source of alternative, environmentally-friendly bio-insecticides. We tested the crude venom of the predatory ant, Manica rubida, and observed severe fitness costs in the parthenogenetic pea aphid (Acyrthosiphon pisum), a common agricultural pest. Therefore, we explored the M. rubida venom peptidome and identified a novel decapeptide U-MYRTX-MANr1 (NH₂-IDPKVLESLV-CONH₂) using a combination of Edman degradation and de novo peptide sequencing. Although this myrmicitoxin was inactive against bacteria and fungi, it reduced aphid survival and reproduction. Furthermore, both crude venom and U-MYRTX-MANr1 reversibly paralyzed injected aphids and induced a loss of body fluids. Components of M. rubida venom may act on various biological targets including ion channels and hemolymph coagulation proteins, as previously shown for other ant venom toxins. The remarkable insecticidal activity of M. rubida venom suggests it may be a promising source of additional bio-insecticide leads.

Revisiting Polybia paulista wasp venom using shotgun proteomics - Insights into the N-linked glycosylated venom proteins

The partial proteome of Polybia paulista wasp venom was previously reported elsewhere using a gel-dependent approach and resulted in the identification of a limited number of venom toxins. Here, we reinvestigated the P. paulista venom using a gel-free shotgun proteomic approach; the highly dynamic range of this approach facilitated the detection and identification of 1673 proteins, of which 23 venom proteins presented N-linked glycosylation as a posttranslational modification. Three different molecular forms of PLA1 were identified as allergenic proteins, and two of these forms were modified by N-linked glycosylation. This study reveals an extensive repertoire of hitherto undescribed proteins that were classified into the following six different functional groups: (i) typical venom proteins; (ii) proteins related to the folding/conformation and PTMs of toxins; (iii) proteins that protect toxins from oxidative stress; (iv) proteins involved in chemical communication; (v) housekeeping proteins; and (vi) uncharacterized proteins. It was possible to identify venom toxin-like proteins that are commonly reported in other animal venoms, including arthropods such as spiders and scorpions. Thus, the findings reported here may contribute to improving our understanding of the composition of P. paulista venom, its envenoming mechanism and the pathologies experienced by the victim after the wasp stinging accident. BIOLOGICAL SIGNIFICANCE: The present study significantly expanded the number of proteins identified in P. paulista venom, contributing to improvements in our understanding of the envenoming mechanism produced by sting accidents caused by this wasp. For example, novel wasp venom neurotoxins have been identified, but no studies have assessed the presence of this type of toxin in social wasp venoms. In addition, 23 N-linked glycosylated venom proteins were identified in the P. paulista venom proteome, and some of these proteins might be relevant allergens that are immunoreactive to human IgE.

Samsum Ant Venom Exerts Anticancer Activity Through Immunomodulation In Vitro and In Vivo

Samsum ant venom (SAV) is a rich repertoire of natural compounds with tremendous pharmacological properties. The present work explores its antineoplastic activity in different cell lines followed by its confirmation in vivo. The cell lines, HepG2, MCF-7, and LoVo showed the differential dose-dependent antineoplastic effect with an increased level of significant cytokines, including Interleukin (IL)-1β, IL-6, and IL-8 and transcription factor, Nuclear factor-kappa B (NF-κB). However, the venom was more effective on HepG2 and MCF-7 cells than LoVo cells. Furthermore, the extract was administered to four groups (n = 8) of rats. Group I was taken as a control without any treatment, whereas group II received CCl₄ (1 mL/kg) for induction of mild hepatoma. Group III was given 100 μg/kg of SAV twice a week for 1 month. Group IV was pretreated with the CCl₄ (like group II) followed by dosing with SAV (100 μg/kg) for 2 months as per the authors' prestandardized dosing schedule. Intriguingly, the rats of group IV demonstrated significant decrease in key cytokines, IL-1β and IL-6, as well as the transcription factors, including Tumor Necrosis Factor-alpha (TNF-α), NF-κB, and Inhibitor-kappa B (I-κB) as compared with group II. Furthermore, increase in IL-10 and First apoptosis signal (FAS) in the same group confirmed that SAV induces apoptosis at the given dose through immunomodulation leading to enhanced tumor killing in vivo. Hence, SAV has an excellent antineoplastic activity that can be directly used to treat certain types of cancer. Moreover, study of its ingredients can pave ways to design novel anticancer drugs. However, further in-depth investigation is required before its clinical trials.

A comprehensive portrait of the venom of the giant red bull ant, Myrmecia gulosa, reveals a hyperdiverse hymenopteran toxin gene family

Ants (Hymenoptera: Formicidae) are diverse and ubiquitous, and their ability to sting is familiar to many of us. However, their venoms remain largely unstudied. We provide the first comprehensive characterization of a polypeptidic ant venom, that of the giant red bull ant, Myrmecia gulosa. We reveal a suite of novel peptides with a range of posttranslational modifications, including disulfide bond formation, dimerization, and glycosylation. One venom peptide has sequence features consistent with an epidermal growth factor fold, while the remaining peptides have features suggestive of a capacity to form amphipathic helices. We show that these peptides are derived from what appears to be a single, pharmacologically diverse, gene superfamily (aculeatoxins) that includes most venom peptides previously reported from the aculeate Hymenoptera. Two aculeatoxins purified from the venom were found to be capable of activating mammalian sensory neurons, consistent with the capacity to produce pain but via distinct mechanisms of action. Further investigation of the major venom peptide MIITX1-Mg1a revealed that it can also incapacitate arthropods, indicative of dual utility in both defense and predation. MIITX1-Mg1a accomplishes these functions by generating a leak in membrane ion conductance, which alters membrane potential and triggers neuronal depolarization. Our results provide the first insights into the evolution of the major toxin gene superfamily of the aculeate Hymenoptera and provide a new paradigm in the functional evolution of toxins from animal venoms.

Wasp venomic: Unravelling the toxins arsenal of Polybia paulista venom and its potential pharmaceutical applications

Polybia paulista (Hymenoptera: Vespidae) is a neotropical social wasp from southeast Brazil. As most social Hymenoptera, venom from P. paulista comprises a complex mixture of bioactive toxins ranging from low molecular weight compounds to peptides and proteins. Several efforts have been made to elucidate the molecular composition of the P. paulista venom. Data derived from proteomic, peptidomic and allergomic analyses has enhanced our understanding of the whole envenoming process caused by the insect sting. The combined use of bioinformatics, -omics- and molecular biology tools have allowed the identification, characterization, in vitro synthesis and recombinant expression of several wasp venom toxins. Some of these P. paulista - derived bioactive compounds have been evaluated for the rational design of antivenoms and the improvement of allergy specific diagnosis and immunotherapy. Molecular characterization of crude venom extract has enabled the description and isolation of novel toxins with potential biotechnological applications. Here, we review the different approaches that have been used to unravel the venom composition of P. paulista. We also describe the main groups of P. paulista - venom toxins currently identified and analyze their potential in the development of component-resolved diagnosis of allergy, and in the rational design of antivenoms and novel bioactive drugs.

Pharmacological screening technologies for venom peptide discovery

Venomous animals occupy one of the most successful evolutionary niches and occur on nearly every continent. They deliver venoms via biting and stinging apparatuses with the aim to rapidly incapacitate prey and deter predators. This has led to the evolution of venom components that act at a number of biological targets - including ion channels, G-protein coupled receptors, transporters and enzymes - with exquisite selectivity and potency, making venom-derived components attractive pharmacological tool compounds and drug leads. In recent years, plate-based pharmacological screening approaches have been introduced to accelerate venom-derived drug discovery. A range of assays are amenable to this purpose, including high-throughput electrophysiology, fluorescence-based functional and binding assays. However, despite these technological advances, the traditional activity-guided fractionation approach is time-consuming and resource-intensive. The combination of screening techniques suitable for miniaturization with sequence-based discovery approaches - supported by advanced proteomics, mass spectrometry, chromatography as well as synthesis and expression techniques - promises to further improve venom peptide discovery. Here, we discuss practical aspects of establishing a pipeline for venom peptide drug discovery with a particular emphasis on pharmacology and pharmacological screening approaches. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

Identification of the immunogenic epitopes of the whole venom component of the Hemiscorpius lepturus scorpion using the phage display peptide library

The venom of the Hemiscorpius lepturus scorpion contains mixtures of bioactive compounds that disturb biochemical and physiological functions of the victims. Hemiscorpius lepturus envenomation is recognized as a serious health concern in tropical regions. So far, there is no preventive procedure, and the main focus is on treatment of victims with an antiserum purified from hyper-immunized horses. Although antisera can neutralize the venom, they, in some cases, lead to anaphylactic shock and even death. Selection of peptides mimicking antigenic and immunogenic epitopes of toxins from random peptide libraries is a novel approach for the development of recombinant toxins and poly-epitopic vaccine. To achieve this aim, a phage display peptide library and three rounds of biopanning were performed on immobilized antibodies (IgGs) purified from the sera of hyper-immunized horses. The results show that the highest binding of the phage to immobilized horse antibodies occurred in the third round of biopanning. Over 125 individual clones carrying mimotopes of Hemiscorpius lepturus toxins were selected and subjected for sequencing. The sequencing results identified unique peptides mimicking the antigenic and immunogenic epitopes of Hemiscorpius lepturus toxins. The results of this study provide a basis for further studies and the development of a putative epitopic vaccine and a recombinant toxin.

[Ants: a chemical library of anticancer molecules]

Animal venoms are complex mixtures containing simple organic molecules, proteins, peptides, and other bioactive elements with extraordinary biological properties associated with their ability to act on a number of molecular receptors in the process of incapacitating their target organisms. In such a context, arthropod venoms are invaluable sources of bioactive substances, with therapeutic interest but the limited availability of some venom such as those from ants, has restricted the potential that these biomolecules could represent. We investigated for the first time transcriptomic expression from the ant species Tetramorium bicarinatum. Four hundred randomly selected clones from cDNA libraries were sequenced and a total of 374 expressed sequence tags (ESTs) were generated. Based on the results of BLAST searches, these sequences were clustered and assembled into 269 contigs. About 72% (269) of these matched BLASTx hits with an interesting diversity and unusual abundance of cellular transcripts (48%) related to gene and protein expression reflecting the specialization of this tissue. In addition, transcripts encoding transposases were relatively highly expressed (14%). It may be that transposable elements are present and that their presence accounts for some of the variation in venom toxins. About twenty per cent of the ESTs were categorized as putative toxins, the major part represented by allergens (48% of the total venom toxins) such as pilosulin 5, sol i 3 and Myp p I and II. Several contigs encoding enzymes, including zinc-metalloproteases (17%) that are likely involved in the processing and activation of venom proteins/peptides, were also identified from the library. In addition, a number of sequences (8%) had no significant similarity to any known sequence which indicates a potential source of for the discovery of new toxins. In order to provide a global insight on the transcripts expressed in the venom gland of the Brazilian ant species Tetramorium bicarinatum and to unveil the potential of their products, high-throughput expressed sequence tags were generated using Illumina paired-end sequencing technology. A total of 212 371 758 pairs of quality-filtered, 100-base-pair Illumina reads were obtained. The de novo assemblies yielded 36 042 contigs for which 27 873 have at least one predicted ORF among which 59.77% produce significant hits in the available databases. The investigation of the read mapping toxin class revealed and confirmed a high diversification with the major part consistent with the classical hymenopteran venom protein signature represented by venom allergen (33.3%) followed by a diverse toxin-expression profile including several distinct isoforms of phospholipase A1 and A2, venom serine protease, hyaluronidase, protease inhibitor and secapin. Moreover, our results revealed for the first time the presence of toxin-like peptides that have been previously identified from unrelated venomous animals such as waprin-like (snakes) and agatoxins (spiders and conus). These studies provide a first insight of the gene expression scenario of the venom gland of T. bicarinatum which might contribute to acquiring a more comprehensive view about the origin and functional diversity of venom proteins of this ant. Based on such results, we conducted cytotoxic tests from the crude venom of T.bicarinatum ant and reported toxic effect on tumoral cells lines from one of the fifth of the most frequently occurring cancers with a 3-year survival rate of only 30%. In such a context, new therapeutic strategies are essential and the discovery of new molecules in ant venom could be one possible avenue. Thus our project aims to characterize, from the crude venom of T.bicarinatum, the molecule(s) which have potential anti-cancerous toxicity as well as their mechanisms of action.

The Biochemical Toxin Arsenal from Ant Venoms

Ants (Formicidae) represent a taxonomically diverse group of hymenopterans with over 13,000 extant species, the majority of which inject or spray secretions from a venom gland. The evolutionary success of ants is mostly due to their unique eusociality that has permitted them to develop complex collaborative strategies, partly involving their venom secretions, to defend their nest against predators, microbial pathogens, ant competitors, and to hunt prey. Activities of ant venom include paralytic, cytolytic, haemolytic, allergenic, pro-inflammatory, insecticidal, antimicrobial, and pain-producing pharmacologic activities, while non-toxic functions include roles in chemical communication involving trail and sex pheromones, deterrents, and aggregators. While these diverse activities in ant venoms have until now been largely understudied due to the small venom yield from ants, modern analytical and venomic techniques are beginning to reveal the diversity of toxin structure and function. As such, ant venoms are distinct from other venomous animals, not only rich in linear, dimeric and disulfide-bonded peptides and bioactive proteins, but also other volatile and non-volatile compounds such as alkaloids and hydrocarbons. The present review details the unique structures and pharmacologies of known ant venom proteinaceous and alkaloidal toxins and their potential as a source of novel bioinsecticides and therapeutic agents.

Biological and Enzymatic Characterization of Proteases from Crude Venom of the Ant Odontomachus bauri

Hymenoptera venoms constitute an interesting source of natural toxins that may lead to the development of novel therapeutic agents. The present study investigated the enzymatic and biological characteristics of the crude venom of the ant Odontomachus bauri. Its crude venom presents several protein bands, with higher staining for six proteins with gelatinolytic activity (17, 20, 26, 29, 43 and 48 kDa). The crude venom showed high proteolytic activity on azocasein at optimal pH 8.0 and 37 °C. In the presence of protease inhibitors as aprotinin, leupeptin and EDTA, the azocaseinolytic activity was reduced by 45%, 29% and 9%, respectively, suggesting that the enzymes present in the crude venom belong to the three classes of proteases, with the serine proteases in greater intensity. The crude venom degraded the fibrinogen α-chain faster than the β-chain, while the fibrinogen γ-chain remained unchanged. In biological assays, O. bauri venom showed hemolytic and coagulant activity in vitro, and defibrinating activity in vivo. In addition, the venom showed antimicrobial activity against Staphylococcus aureus and Escherichia coli as well as antiparasitic activity on Toxoplasma gondii infection in vitro. In that sense, this study sheds perspectives for pharmacological applications of O. bauri venom enzymes.

Facing Hymenoptera Venom Allergy: From Natural to Recombinant Allergens

Along with food and drug allergic reactions, a Hymenoptera insect Sting (Apoidea, Vespidae, Formicidae) is one of the most common causes of anaphylaxis worldwide. Diagnoses of Hymenoptera venom allergy (HVA) and specific immunotherapy (SIT) have been based on the use of crude venom extracts. However, the incidence of cross-reactivity and low levels of sensibility during diagnosis, as well as the occurrence of nonspecific sensitization and undesired side effects during SIT, encourage the search for novel allergenic materials. Recombinant allergens are an interesting approach to improve allergy diagnosis and SIT because they circumvent major problems associated with the use of crude venom. Production of recombinant allergens depends on the profound molecular characterization of the natural counterpart by combining some “omics” approaches with high-throughput screening techniques and the selection of an appropriate system for heterologous expression. To date, several clinically relevant allergens and novel venom toxins have been identified, cloned and characterized, enabling a better understanding of the whole allergenic and envenoming processes. Here, we review recent findings on identification, molecular characterization and recombinant expression of Hymenoptera venom allergens and on the evaluation of these heterologous proteins as valuable tools for tackling remaining pitfalls on HVA diagnosis and immunotherapy.

Transcriptomics and venomics: implications for medicinal chemistry

Over the last three decades, transcriptomic studies of venom gland cells have continuously evolved, opening up new possibilities for exploring the molecular diversity of animal venoms, a prerequisite for the discovery of new drug candidates and molecular phylogenetics. The molecular complexity of animal venoms is much greater than initially thought. In this review, we describe the different technologies available for transcriptomic studies of venom, from the original individual cloning approaches to the more recent global Next Generation Sequencing strategies. Our understanding of animal venoms is evolving, with the discovery of complex and diverse bio-optimized cocktails of compounds, including mostly peptides and proteins, which are now beginning to be studied by academic and industrial researchers.

Whole Transcriptome of the Venom Gland from Urodacus yaschenkoi Scorpion

Australian scorpion venoms have been poorly studied, probably because they do not pose an evident threat to humans. In addition, the continent has other medically important venomous animals capable of causing serious health problems. Urodacus yaschenkoi belongs to the most widely distributed family of Australian scorpions (Urodacidae) and it is found all over the continent, making it a useful model system for studying venom composition and evolution. This communication reports the whole set of mRNA transcripts produced by the venom gland. U. yaschenkoi venom is as complex as its overseas counterparts. These transcripts certainly code for several components similar to known scorpion venom components, such as: alpha-KTxs, beta-KTxs, calcins, protease inhibitors, antimicrobial peptides, sodium-channel toxins, toxin-like peptides, allergens, La1-like, hyaluronidases, ribosomal proteins, proteasome components and proteins related to cellular processes. A comparison with the venom gland transcriptome of Centruroides noxius (Buthidae) showed that these two scorpions have similar components related to biological processes, although important differences occur among the venom toxins. In contrast, a comparison with sequences reported for Urodacus manicatus revealed that these two Urodacidae species possess the same subfamily of scorpion toxins. A comparison with sequences of an U. yaschenkoi cDNA library previously reported by our group showed that both techniques are reliable for the description of the venom components, but the whole transcriptome generated with Next Generation Sequencing platform provides sequences of all transcripts expressed. Several of which were identified in the proteome, but many more transcripts were identified including uncommon transcripts. The information reported here constitutes a reference for non-Buthidae scorpion venoms, providing a comprehensive view of genes that are involved in venom production. Further, this work identifies new putative bioactive compounds that could be used to seed research into new pharmacological compounds and increase our understanding of the function of different ion channels.

De Novo sequencing and transcriptome analysis for Tetramorium bicarinatum: a comprehensive venom gland transcriptome analysis from an ant species

BACKGROUND

Arthropod venoms are invaluable sources of bioactive substances with biotechnological application. The limited availability of some venoms, such as those from ants, has restricted the knowledge about the composition and the potential that these biomolecules could represent. In order to provide a global insight on the transcripts expressed in the venom gland of the Brazilian ant species Tetramorium bicarinatum and to unveil the potential of its products, high-throughput approach using Illumina technology has been applied to analyze the genes expressed in active venom glands of this ant species.

RESULTS

A total of 212,371,758 pairs of quality-filtered, 100-base-pair Illumina reads were obtained. The de novo assemblies yielded 36,042 contigs for which 27,873 have at least one predicted ORF among which 59.77% produce significant hits in the available databases. The investigation of the reads mapping toxin class revealed a high diversification with the major part consistent with the classical hymenopteran venom protein signature represented by venom allergen (33.3%), followed by a diverse toxin-expression profile including several distinct isoforms of phospholipase A1 and A2, venom serine protease, hyaluronidase, protease inhibitor and secapin. Moreover, our results revealed for the first time the presence of toxin-like peptides that have been previously identified from unrelated venomous animals such as waprin-like (snakes) and agatoxins (spiders and conus).The non-toxin transcripts were mainly represented by contigs involved in protein folding and translation, consistent with the protein-secretory function of the venom gland tissue. Finally, about 40% of the generated contigs have no hits in the databases with 25% of the predicted peptides bearing signal peptide emphasizing the potential of the investigation of these sequences as source of new molecules. Among these contigs, six putative novel peptides that show homologies with previously identified antimicrobial peptides were identified.

CONCLUSIONS

To the best of our knowledge, this work reports the first large-scale analysis of genes transcribed by the venomous gland of the ant species T. bicarinatum and helps with the identification of Hymenoptera toxin arsenal. In addition, results from this study demonstrate that de novo transcriptome assembly allows useful venom gene expression analysis in a species lacking a genome sequence database.

Diversity of peptide toxins from stinging ant venoms

Ants (Hymenoptera: Formicidae) represent a taxonomically diverse group of arthropods comprising nearly 13,000 extant species. Sixteen ant subfamilies have individuals that possess a stinger and use their venom for purposes such as a defence against predators, competitors and microbial pathogens, for predation, as well as for social communication. They exhibit a range of activities including antimicrobial, haemolytic, cytolytic, paralytic, insecticidal and pain-producing pharmacologies. While ant venoms are known to be rich in alkaloids and hydrocarbons, ant venoms rich in peptides are becoming more common, yet remain understudied. Recent advances in mass spectrometry techniques have begun to reveal the true complexity of ant venom peptide composition. In the few venoms explored thus far, most peptide toxins appear to occur as small polycationic linear toxins, with antibacterial properties and insecticidal activity. Unlike other venomous animals, a number of ant venoms also contain a range of homodimeric and heterodimeric peptides with one or two interchain disulfide bonds possessing pore-forming, allergenic and paralytic actions. However, ant venoms seem to have only a small number of monomeric disulfide-linked peptides. The present review details the structure and pharmacology of known ant venom peptide toxins and their potential as a source of novel bioinsecticides and therapeutic agents.

Linear antimicrobial peptides from Ectatomma quadridens ant venom

Venoms from three poneromorph ant species (Paraponera clavata, Ectatomma quadridens and Ectatomma tuberculatum) were investigated for the growth inhibition of Gram-positive and Gram-negative bacteria. It was shown that the venom of E. quadridens and its peptide fraction in particular possess marked antibacterial action. Three linear antimicrobial peptides sharing low similarity to the well-known ponericin peptides were isolated from this ant venom by means of size-exclusion and reversed-phase chromatography. The peptides showed antimicrobial activity at low micromolar concentrations. Their primary structure was established by direct Edman sequencing in combination with mass spectrometry. The most active peptide designated ponericin-Q42 was chemically synthesized. Its secondary structure was investigated in aqueous and membrane-mimicking environment, and the peptide was shown to be partially helical already in water, which is unusual for short linear peptides. Analysis of its activity on different bacterial strains, human erythrocytes and chronic myelogenous leukemia K562 cells revealed that the peptide shows broad spectrum cytolytic activity at micromolar and submicromolar concentrations. Ponericin-Q42 also possesses weak toxic activity on flesh fly larvae with LD50 of ∼105 μg/g.

Production of antibacterial peptide from bee venom via a new strategy for heterologous expression

Honey bee is important economic insect that not only pollinates fruits and crops but also provides products with various physiological activities. Bee venom is a functional agent that is widely applied in clinical treatment and pharmacy. Secapin is one of these agents that have a significant role in therapy. The functions of secapin from the bee venom have been documented, but little information is known about its heterologous expression under natural condition. Moreover, few scholars verified experimentally the functions of secapin from bee venom in vitro. In this study, we successfully constructed a heterologous expression vector, which is different from conventional expression system. A transgenic approach was established for transformation of secapin gene from the venom of Apis mellifera carnica (Ac-sec) into the edible fungi, Coprinus cinereus. Ac-sec was encoded by a 234 bp nucleotide that contained a signal peptide domain and two potential phosphorylation sites. The sequence exhibited highly homology with various secapins characterized from honey bee and related species. Southern blot data indicated that Ac-sec was present as single or multiple copy loci in the C. cinereus genome. By co-transformation and double-layer active assay, Ac-sec was expressed successfully in C. cinereus and the antibacterial activity of the recombinants was identified, showing notable antibacterial activities on different bacteria. Although Ac-sec is from the venom of Apidae, phylogenetic analysis demonstrated that Ac-sec was more closely related to that of Vespid than to bee species from Apidae. The molecular characteristics of Ac-sec and the potential roles of small peptides in biology were discussed.

Antioxidant bioactivity of Samsum ant (Pachycondyla sennaarensis) venom protects against CCL₄-induced nephrotoxicity in mice

To assess whether SAV could influence the effects of carbon tetrachloride (CCL4) exposure, mice were treated with SAV in doses of 100, 200, 300 and 400  μg/kg body weight and the effects on oxidative status and kidney function were studied. Serum levels of creatinine, malondialdehyde (MDA), and blood urea, together with renal and hepatic levels of MDA, glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) were quantified in order to evaluate antioxidant activity. Results showed that the group injected with CCL4 exhibited significantly higher levels of oxidative stress markers, MDA, and significantly lower concentrations of GSH, SOD and catalase. SAV was found to significantly improve these oxidative markers, occasionally, in a dose-dependent manner. Furthermore, treatment with SAV was associated with the same behaviour in respect to kidney functions which had previously been impaired by CCL4. Histopathological examination demonstrated that SAV, in different groups, improved the renal tissue damage induced by CCL4 and histological scores confirmed that significant improvements were obtained after treatment with SAV, particularly with the lowest dose (100  μg/kg body weight). In conclusion, SAV has the potential capability to restore oxidative stability and to improve kidney functions after CCL4 acute injury.

Transcriptome analysis in venom gland of the predatory giant ant Dinoponera quadriceps: insights into the polypeptide toxin arsenal of hymenopterans

Background

Dinoponera quadriceps is a predatory giant ant that inhabits the Neotropical region and subdues its prey (insects) with stings that deliver a toxic cocktail of molecules. Human accidents occasionally occur and cause local pain and systemic symptoms. A comprehensive study of the D. quadriceps venom gland transcriptome is required to advance our knowledge about the toxin repertoire of the giant ant venom and to understand the physiopathological basis of Hymenoptera envenomation.

Results

We conducted a transcriptome analysis of a cDNA library from the D. quadriceps venom gland with Sanger sequencing in combination with whole-transcriptome shotgun deep sequencing. From the cDNA library, a total of 420 independent clones were analyzed. Although the proportion of dinoponeratoxin isoform precursors was high, the first giant ant venom inhibitor cysteine-knot (ICK) toxin was found. The deep next generation sequencing yielded a total of 2,514,767 raw reads that were assembled into 18,546 contigs. A BLAST search of the assembled contigs against non-redundant and Swiss-Prot databases showed that 6,463 contigs corresponded to BLASTx hits and indicated an interesting diversity of transcripts related to venom gene expression. The majority of these venom-related sequences code for a major polypeptide core, which comprises venom allergens, lethal-like proteins and esterases, and a minor peptide framework composed of inter-specific structurally conserved cysteine-rich toxins. Both the cDNA library and deep sequencing yielded large proportions of contigs that showed no similarities with known sequences.

Conclusions

To our knowledge, this is the first report of the venom gland transcriptome of the New World giant ant D. quadriceps. The glandular venom system was dissected, and the toxin arsenal was revealed; this process brought to light novel sequences that included an ICK-folded toxins, allergen proteins, esterases (phospholipases and carboxylesterases), and lethal-like toxins. These findings contribute to the understanding of the ecology, behavior and venomics of hymenopterans.