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Organization of wasp venom glands. (A) Overall organization of the venom apparatus. From posterior (p) to anterior (a) are, ovipositor (O), reservoir (R) and venom gland (VG). The venom gland and the reservoir are joined by a narrow connecting duct. (B) Confocal images of venom glands from parasitoids showing diversity in shape and size: Leptopilina spp. have elongated glands, the G. xanthopoda gland is sac-shaped, whereas that of C. sonorensis is branched. F-actin-rich structures (red), and occasionally, muscles (m) connected to the ovipositor are visible. a, anterior; p, posterior. Scale bar, 100 μm. Objective: Plan-Apochromat 20/0.8. (C) Secretory cells with large nuclei (arrows) contain the canal-like structures (c); intimal layer cells, with small nuclei (arrowheads, nuclei not visible in all images), line the lumen (L) of the venom gland. Scale bar, 5 μm. Objective: Plan-Apochromat 63/1.4, oil differential interference contrast (DIC) optics. (D) Threedimensional reconstruction of L. heterotoma venom gland, secretory cell nuclei (blue), actin canals (c, red) and intimal cell layer (green). a, anterior; p, posterior.
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Parasitoid wasps produce virulence factors that bear significant resemblance to viruses and have the ability to block host defense responses. The function of these virulence factors, produced predominantly in wasp venom glands, and the ways in which they interfere with host development and physiology remain mysterious. Here, we report the discovery...
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... wasp can be divided into three main regions. The posterior end bears a long chitinous ovipositor, responsible for the delivery of eggs and venom into the host, a reservoir in which the venom is stored, and a venom gland, which produces and secretes the components of the venom. All the species considered here share this tripartite organization ( Fig. 2A), even though some features (e.g. shape and size of the venom gland, length of the duct connecting the gland to the reservoir, or size of the reservoir itself) ...
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... images of DAPI/TRITC-phalloidin-labeled venom glands show that despite differences in size and shape, all glands share the presence of prominent actin-rich structures inside their cells (Fig. 2B). In venom glands of all five wasps, two different cell types are distinguished: first, small and narrow cells that line the lumen of the venom gland. We have previously referred to this layer of cells as the intimal layer in venom glands of L. heterotoma and L. victoriae (Morales et al., 2005;Chiu et al., 2006). This cell layer is ...
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... that line the lumen of the venom gland. We have previously referred to this layer of cells as the intimal layer in venom glands of L. heterotoma and L. victoriae (Morales et al., 2005;Chiu et al., 2006). This cell layer is apposed to a second, peripheral layer of larger, evidently polyploid, secretory cells, which contain the actin-lined canals (Fig. 2B). A three-dimensional reconstruction of L. heterotoma venom gland confirms that each secretory cell only has one unbranched canal that originates roughly perpendicular to the long axis of the venom gland (Fig. 2C,D). The large nucleus of the secretory cell is found peripherally, whereas nuclei of the smaller cells of the intimal layer ...
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... layer is apposed to a second, peripheral layer of larger, evidently polyploid, secretory cells, which contain the actin-lined canals (Fig. 2B). A three-dimensional reconstruction of L. heterotoma venom gland confirms that each secretory cell only has one unbranched canal that originates roughly perpendicular to the long axis of the venom gland (Fig. 2C,D). The large nucleus of the secretory cell is found peripherally, whereas nuclei of the smaller cells of the intimal layer are located deeper within the organ (Fig. ...
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... of L. heterotoma venom gland confirms that each secretory cell only has one unbranched canal that originates roughly perpendicular to the long axis of the venom gland (Fig. 2C,D). The large nucleus of the secretory cell is found peripherally, whereas nuclei of the smaller cells of the intimal layer are located deeper within the organ (Fig. ...
Citations
... S8A). Similar actin-rich structures have been described in certain wasp venom glands termed long glands (25). In ultrastructural analysis, actin-rich microvilli of venom gland cells surrounded duct-like cuticles, representing presumptive exit sites of venom secretion (Fig. 4M). ...
Parasitoid wasps, one of the most diverse and species-rich animal taxa on Earth, produce venoms that manipulate host development and physiology to exploit host resources. However, mechanisms of venom action remain poorly understood. Here, we show that infection of host Drosophila by the endoparasitoid wasp, Asobara japonica , triggers imaginal disc degradation (IDD) by inducing apoptosis, autophagy, and mitotic arrest, leading to impaired host metamorphosis. A multi-omics approach identified two venom proteins of A. japonica necessary for IDD. Knockdown experiments targeting the venom genes revealed that in concert with host immune suppression, IDD is essential for successful parasitism. Our study highlights a venom-mediated hijacking strategy of the parasitoid wasp that allows host larvae to grow, but ultimately kills the hosts.
... The venom gland of hymenopteran species, which is primarily composed of secretory epithelial cells, serves as a specialized organ for protein synthesis and secretion (Ferrarese et al. 2009). Consequently, this may provide viruses with a suitable environment for replication and secretion into the venom. ...
To identify viruses and compare their abundance levels in the venom glands of hymenopteran species, we conducted venom gland‐specific transcriptome assemblies and analyses of 22 aculeate bees and wasps and identified the RNA genomes of picornaviruses. Additionally, we investigated the expression patterns of viruses in the venom glands over time following capture. Honeybee‐infecting viruses, including the black queen cell virus (BQCV), the deformed wing virus (DWV) and the Israeli acute paralysis virus (IAPV), were highly expressed in the venom glands of Apis mellifera and social wasps. This finding suggests that the venom of bees and wasps is likely to contain these viruses, which can be transmitted horizontally between species through stinger use. Apis mellifera exhibited an increasing pattern of abundance levels for BQCV, DWV, IAPV and Triatovirus , whereas the social wasp Vespa crabro showed increasing abundance levels of IAPV and Triatovirus over different capture periods. This suggests that the venom glands of honeybees and wasps may provide suitable conditions for active viral replication and may be an organ for virus accumulation and transmission. Some viral sequences clearly reflected the phylogeny of aculeate species, implying host‐specific virus evolution. On the other hand, other viruses exhibited unique evolutionary patterns of phylogeny, possibly caused by specific ecological interactions. Our study provides insights into the composition and evolutionary properties of viral genes in the venom glands of certain aculeate bees and wasps, as well as the potential horizontal transmission of these viruses among bee and wasp species.
... For gland histology, we use the terminology of Noirot and Quennedey (1974). We designate the gland cells as secretory cells, and the secretion organelle that these cells contain, sometimes called vesicular organelle or rough canal, as end apparatus (Dierckx 1899, Ratcliffe and King 1969, van Marle and Piek 1986, Ferrarese et al. 2009). The secretory cells are connected to the central lumen of the gland by ducts, or smooth canals (Noirot andQuennedey 1974, Ferrarese et al. 2009). ...
... Based on SBFSEM and CLSM, venom glands of the Cynipini A. erinacei, A. quercushirta, and D. quercusmamma contained 2 cell types: cells located at the periphery and characterized by large polyploid nuclei and an actin-rich region, and an intimal cell layer surrounding the central lumen comprising cells with small nuclei (Fig. 9A). The same 2 cell types were encountered in the venom glands of parasitoid cynipoids and corresponded, respectively, to secretory cells and intimal layer cell (Ferrarese et al. 2009). Secretions thus derive from secretory cells and travel through channels to a central lumen which carries secretions to the venom reservoir. ...
... In secretory cells, the actin-rich region is called the "end apparatus" and corresponds to the actin filaments associated with the microvilli typically encountered in the secretory region of class III gland cells (Noirot andQuennedey 1974, Ferrarese et al. 2009). Contrary to parasitoid cynipoids whose secretory regions are ≤ 10 μm long and straight and perpendicular to the lumen axis (Ferrarese et al. 2009), the end apparatus of the secretory cells of D. quercusmamma venom gland was curved and longer than 20 μm (Fig. 9A, B). The venom gland of A. erinacei was similar (Fig. 9C). ...
Many herbivorous insect species are capable of hijacking plant development to induce novel plant organs called galls. In most groups of galling insects, the insect organs and molecular signals involved in gall induction are poorly understood. We focused on gall wasps (Hymenoptera:Cynipidae), the second largest clade of gall inducers (~1,400 spp.), for which the developmental stages and organs responsible for gall development are unclear. We investigated the female metasomal anatomy of 69 gall-inducing and 29 non-gall-inducing species across each of the major lineages of Cynipoidea, to test relationships between this lifestyle and the relative size of secretory organs. We confirmed that the venom apparatus in gall-inducing species is greatly expanded, although gall-inducing lineages vary in the relative size of these glands. Among these gallers, we measured the largest venom gland apparatus relative to body size ever recorded in insects. Non-galling inquiline species are accompanied by a reduction of this apparatus. Comparative microscopic analysis of venom glands suggests varying venom gland content across the lineages. Some oak gallers also had enlarged accessory glands, a lipid-rich organ whose function remains unclear, and which has not been previously studied in relation to gall formation. Together, the massive expansion of secretory organs specifically in gall-inducing species suggests a role of these secretions in the process of gall formation, and the variance in size of venom glands, accessory glands, and the contents of these glands among gallers, suggests that gall formation across this clade is likely to employ a diversity of molecular strategies.
... near curvimaculatus has a positively charged N-terminal, which was in contrast to the classical signal peptides containing basic residues, and it is speculated that Hymenoptera may have evolved specialized protein processing and secretion pathways [20,46]. A researcher reported the involvement of a channel system linked via actin in the VG of five parasitic wasps in the synthesis and release of venom parasitic factors [47]. Therefore, the proteins without a signal peptide could also be secreted into the host by the parasitoid wasp. ...
... In the recent studies of parasitoid wasp venom proteins, the histone protein was reported as a venom protein only in Chouioia cunea [54], and the second most abundant proteins were actin proteins. Actin might be involved in the transport of venom proteins in parasitoid wasps and in their hosts [47]. ...
Habrobracon hebetor is a parasitoid wasp capable of infesting many lepidopteran larvae. It uses venom proteins to immobilize host larvae and prevent host larval development, thus playing an important role in the biocontrol of lepidopteran pests. To identify and characterize its venom proteins, we developed a novel venom collection method using an artificial host (ACV), i.e., encapsulated amino acid solution in paraffin membrane, allowing parasitoid wasps to inject venom. We performed protein full mass spectrometry analysis of putative venom proteins collected from ACV and venom reservoirs (VRs) (control). To verify the accuracy of proteomic data, we also collected venom glands (VGs), Dufour’s glands (DGs) and ovaries (OVs), and performed transcriptome analysis. In this paper, we identified 204 proteins in ACV via proteomic analysis; compared ACV putative venom proteins with those identified in VG, VR, and DG via proteome and transcriptome approaches; and verified a set of them using quantitative real-time polymerase chain reaction. Finally, 201 ACV proteins were identified as potential venom proteins. In addition, we screened 152 and 148 putative venom proteins identified in the VG transcriptome and the VR proteome against those in ACV, and found only 26 and 25 putative venom proteins, respectively, were overlapped with those in ACV. Altogether, our data suggest proteome analysis of ACV in combination with proteome–transcriptome analysis of other organs/tissues will provide the most comprehensive identification of true venom proteins in parasitoid wasps.
... In many parasitoid species, including L. heterotoma, venom also includes virus-like particles (Chiu et al., 2006;Colinet et al., 2013;Coulette et al., 2017;Goecks et al., 2013;Morales et al., 2005;Rizki et al., 1990). Virus-like particles are produced in an accessory gland, also called the long gland or venom gland (Ferrarese et al., 2009;Rizki et al., 1990), and matured in a separate reservoir within the female wasp's reproductive system (Chiu et al., 2006;Morales et al., 2005). Virus-like particles appear to be devoid of nucleic acids, but contain various proteins, among which the most abundant protein, p40, is located on the surface and spikes of mature particles (Chiu et al., 2006). ...
The parasitoid Leptopilina heterotoma has been used as a model system for more than 70 years, contributing greatly to diverse research areas in ecology and evolution. Here, we synthesized the large body of work on L. heterotoma with the aim to identify new research avenues that could be of interest also for researchers studying other parasitoids and insects. We start our review with a description of typical L. heterotoma characteristics, as well as that of the higher taxonomic groups to which this species belongs. We then continue discussing host suitability and immunity, foraging behaviors, as well as fat accumulation and life histories. We subsequently shift our focus towards parasitoid‐parasitoid interactions, including L. heterotoma coexistence within the larger guild of Drosophila parasitoids, chemical communication, as well as mating and population structuring. We conclude our review by highlighting the assets of L. heterotoma as a model system, including its intermediate life history syndromes, the ease of observing and collecting natural hosts and wasps, as well as recent genomic advances. The parasitoid Leptopilina heterotoma has been used as a model system in biology for more than 70 years. This review aims to provide a broad and detailed synthesis of the work performed on this system, including immunity, behavioral ecology, endosymbiotic and trophic interactions, as well as physiology. Overall, the scientific literature on L. heterotoma unites research based on field observations and experiments, as well as laboratory studies, highlighting the versatility of this model system.
... The dissected venom apparatus from M. pulchricornis female wasps ( Figure 1A) consists of two filamentous venom glands and a large milky reservoir ( Figure 1B). Observed by transmission electron microscopy (TEM), the cells of the gland ( Figure 1C) show the classic type of glandular venom cells with an internal secretory cell canal (cell glandular canal, cgc) surrounded by microvilli [25]. The glandular cells showed a normal nucleus and had a cytoplasm filled with large vesicles, very often in close proximity to the Golgi apparatus ( Figure 1D). ...
Meteorus pulchricornis (Ichneumonoidea, Braconidae) is an endoparasitoid wasp of lepidopteran caterpillars. Its parasitic success relies on vesicles (named M. pulchricornis Virus-Like Particles or MpVLPs) that are synthesized in the venom gland and injected into the parasitoid host along with the venom during oviposition. In order to define the content and understand the biogenesis of these atypical vesicles, we performed a transcriptome analysis of the venom gland and a proteomic analysis of the venom and purified MpVLPs. About half of the MpVLPs and soluble venom proteins identified were unknown and no similarity with any known viral sequence was found. However, MpVLPs contained a large number of proteins labelled as metalloproteinases while the most abundant protein family in the soluble venom was that of proteins containing the Domain of Unknown Function DUF-4803. The high number of these proteins identified suggests that a large expansion of these two protein families occurred in M. pulchricornis. Therefore, although the exact mechanism of MpVLPs formation remains to be elucidated, these vesicles appear to be “metalloproteinase bombs” that may have several physiological roles in the host including modifying the functions of its immune cells. The role of DUF4803 proteins, also present in the venom of other braconids, remains to be clarified.
... In sister species Lh and Lv, these structures mature in the reservoir and assume a stellate morphology with 4-8 spikes radiating from the center. Mature EVs are roughly 300 nm in diameter, [14,16,[20][21][22]. Packed with more than 150 proteins, EVs are, in part, responsible for divergent physiological outcomes in infected hosts [15,19,23]. ...
The wasps Leptopilina heterotoma parasitize and ingest their Drosophila hosts. They produce extracellular vesicles (EVs) in the venom that are packed with proteins, some of which perform immune suppressive functions. EV interactions with blood cells of host larvae are linked to hematopoietic depletion, immune suppression, and parasite success. But how EVs disperse within the host, enter and kill hematopoietic cells are not well understood. Using an antibody marker for L . heterotoma EVs, we show that these parasite-derived structures are readily distributed within the hosts’ hemolymphatic system. EVs converge around the tightly clustered cells of the posterior signaling center (PSC) of the larval lymph gland, a small hematopoietic organ in Drosophila . The PSC serves as a source of developmental signals in naïve animals. In wasp-infected animals, the PSC directs the differentiation of lymph gland progenitors into lamellocytes. These lamellocytes are needed to encapsulate the wasp egg and block parasite development. We found that L . heterotoma infection disassembles the PSC and PSC cells disperse into the disintegrating lymph gland lobes. Genetically manipulated PSC-less lymph glands remain non-responsive and largely intact in the face of L . heterotoma infection. We also show that the larval lymph gland progenitors use the endocytic machinery to internalize EVs. Once inside, L . heterotoma EVs damage the Rab7- and LAMP-positive late endocytic and phagolysosomal compartments. Rab5 maintains hematopoietic and immune quiescence as Rab5 knockdown results in hematopoietic over-proliferation and ectopic lamellocyte differentiation. Thus, both aspects of anti-parasite immunity, i.e., (a) phagocytosis of the wasp’s immune-suppressive EVs, and (b) progenitor differentiation for wasp egg encapsulation reside in the lymph gland. These results help explain why the lymph gland is specifically and precisely targeted for destruction. The parasite’s simultaneous and multipronged approach to block cellular immunity not only eliminates blood cells, but also tactically blocks the genetic programming needed for supplementary hematopoietic differentiation necessary for host success. In addition to its known functions in hematopoiesis, our results highlight a previously unrecognized phagocytic role of the lymph gland in cellular immunity. EV-mediated virulence strategies described for L . heterotoma are likely to be shared by other parasitoid wasps; their understanding can improve the design and development of novel therapeutics and biopesticides as well as help protect biodiversity.
... Little is known, however, on Ganaspis biology, apart from the fact that at least some Ganaspis species parasitize Drosophila larvae (such as G. brasiliensis and the uncharacterized G. sp used in this study). Some Ganaspsis species have been investigated in terms of immune interaction with the Drosophila (Ferrarese et al. 2009;Mortimer et al. 2013), revealing important differences with Leptopilina species (Mortimer 2013). ...
Some species of parasitic wasps have domesticated viral machineries to deliver immunosuppressive factors to their hosts. Up to now, all described cases fall into the Ichneumonoidea superfamily, which only represents around 10% of hymenoptera diversity, raising the question of whether such domestication occurred outside this clade. Furthermore, the biology of the ancestral donor viruses is completely unknown. Since the 1980’s, we know that Drosophila parasitoids belonging to the Leptopilina genus, which diverged from the Ichneumonoidea superfamily 225My ago, do produce immuno-suppressive virus-like structure in their reproductive apparatus. However, the viral origin of these structures has been the subject of debate. In this paper, we provide genomic and experimental evidence that those structures do derive from an ancestral virus endogenization event. Interestingly, its close relatives induce a behaviour manipulation in present-day wasps. Thus, we conclude that virus domestication is more prevalent than previously thought and that behaviour manipulation may have been instrumental in the birth of such associations.
... Among them are the wasps of the Figitidae family, including the genera Ganaspis and Leptopilina that parasitize Drosophila melanogaster (Diptera) and other closely related species. The venomous EVs of these species differ in shape, size, and structure (12)(13)(14)(15)(16)(17)(18)(19), and former publications called them Virus Like Particles (VLPs) because the mature vesicles somehow resembled viruses, particularly those of L. heterotoma that showed spikes extending from a round/ovoid vesicle (9,18). Recently, a proteomic study of L. heterotoma VLPs showed that they contain many different proteins. ...
... Because the shape of most of these purified vesicles at 100-300 nm appeared to differ from that of the previously "typical" venosomes described in the venom reservoir of L. boulardi strains (13,14), we verified that the procedure did not extensively degrade the venosomes. Since L. heterotoma venosomes, in contrast to L. boulardi ones, have a specific stellate shape due to spike extensions (12,17), we treated the crude venom of this species in the same way and analyzed the obtained pellet by microscopy ( Figure S2). Part of the L. heterotoma pelleted vesicles clearly retained the stellate shape, while others resembled more L. boulardi ISm and ISy vesicles, with the electron dense material accumulated as an asymmetric crescent or distributed all along the membrane [ Figure S2; see also Figure 1E in (12)]. ...
... Therefore, it seems that there is no difference in secretion along the gland between the factors associated and not associated with venosomes. The venosomes of the Figitidae wasps were previously described as having a peculiar assembly in the lumen of the venom gland (15)(16)(17)(18), and we therefore studied further how LbGAP could associate with the ISm venosomes by electron microscopy. For this, ultra-thin sections of the ISm venom apparatus were prepared for immunogold electron microscopy using the LbGAP antibody (Figure 3). Figure 3A show a cross-section through the "canal" of the secretory cells as indicated by the microvilli presence. ...
Endoparasitoid wasps, which lay eggs inside the bodies of other insects, use various strategies to protect their offspring from the host immune response. The hymenopteran species of the genus Leptopilina, parasites of Drosophila, rely on the injection of a venom which contains proteins and peculiar vesicles (hereafter venosomes). We show here that the injection of purified L. boulardi venosomes is sufficient to impair the function of the Drosophila melanogaster lamellocytes, a hemocyte type specialized in the defense against wasp eggs, and thus the parasitic success of the wasp. These venosomes seem to have a unique extracellular biogenesis in the wasp venom apparatus where they acquire specific secreted proteins/virulence factors and act as a transport system to deliver these compounds into host lamellocytes. The level of venosomes entry into lamellocytes of different Drosophila species was correlated with the rate of parasitism success of the wasp, suggesting that this venosome-cell interaction may represent a new evolutionary level of host-parasitoid specificity.
... The venom effect on the hemocytes, the lymph gland or the melanisation has been described for Leptopilina species (Dubuffet et al., 2009;Heavner et al., 2014). The Leptopilina and Ganaspis venom contains not only soluble proteins but also peculiar vesicles with an unclear biogenesis (Rizki and Rizki, 1990;Dubuffet et al., 2009;Ferrarese et al., 2009;Gatti et al., 2012), which are likely involved in parasitic success. These purified vesicles seemingly target the host lamellocytes, changing their shape from discoidal to bipolar, which supposedly prevent them to adhere and form a capsule, or inducing their lysis (Rizki and Rizki, 1984, 1990, 1994. ...
Host-parasitoid interactions are among the most studied interactions between invertebrates because of their fundamental interest-the evolution of original traits in parasitoids-and applied, parasitoids being widely used in biological control. Immunity, and in particular cellular immunity, is central in these interactions, the host encapsulation response being specific for large foreign bodies such as parasitoid eggs. Although already well studied in this species, recent data on Drosophila melanogaster have unquestionably improved knowledge of invertebrate cellular immunity. At the same time, the venomics of parasitoids has expanded, notably those of Drosophila. Here, we summarize and discuss these advances, with a focus on an emerging "time-dependent" view of interactions outcome at the intra-and interspecific level. We also present issues still in debate and prospects for study. Data on the Drosophila-parasitoid model paves the way to new concepts in insect immunity as well as parasitoid wasp strategies to overcome it.
