The genomic and transcriptomic analyses of serine proteases and their homologs in an endoparasitoid, Pteromalus puparum

Genome resequencing and genome-wide polymorphisms in mosquito vectors Aedes aegypti and Aedes albopictus from south India

Aedes aegypti and Aedes albopictus mosquitoes spread major vector-borne viral diseases in tropical and sub-tropical regions of the globe. In this study, we sequenced the genome of Indian Ae. aegypti and Ae. albopictus and mapped to their reference genomes. Comparative genomics were performed between our strain and the reference strains. A total of 14,416,484 single nucleotide polymorphisms (SNPs) and 156,487 insertions and deletions (InDels) were found in Ae. aegypti, and 28,940,433 SNPs and 188,987 InDels in Ae. albopictus. Particular emphasis was given to gene families involved in mosquito digestion, development, and innate immunity, which could be putative candidates for vector control. Serine protease cascades and their inhibitors called serpins, play a central role in these processes. We extracted high-impact variants in genes associated with serine proteases and serpins. This study reports for the first time a high coverage genome sequence data of an Indian Ae. albopictus mosquito. The results from this study will provide insights into Indian Aedes specific polymorphisms and the evolution of immune related genes in mosquitoes, which can serve as a resource for future comparative genomics and those pursuing the development of targeted biopesticides for effective mosquito control strategies.

Exploring the role of the ovary-serine protease gene in the female fertility of the diamondback moth using CRISPR/Cas9

BACKGROUND

Oogenesis is a complex pathway necessary for proper female reproduction in insects. Ovary-serine protease (Osp) is a homologous gene of serine protease Nudel (SpNudel) and plays an essential role in the oogenesis and ovary development of Drosophila melanogaster. However, the function of Osp is not determined in Plutella xylostella, a highly destructive pest of cruciferous crops.

RESULTS

The PxOsp gene comprises a 5883-bp open-reading frame that encodes a protein consisting of 1994 amino acids, which contain four conserved domains. PxOsp exhibited a high relative expression in adult females with a specific expression in the ovary. Through the utilization of CRISPR/Cas9 technology, homozygous mutants of PxOsp were generated. These homozygous mutant females produced fewer eggs (average of 56 eggs/female) than wild-type (WT) females (average of 97 eggs/female) when crossed with WT males, and these eggs failed to hatch. Conversely, mutant males produced normal progeny when crossed with WT females. The ovarioles in homozygous mutant females were significantly shorter (5.02 mm in length) and contained fewer eggs (average of 3 eggs/ovariole) than WT ovarioles (8.09 mm in length with an average of 8 eggs/ovariole). Moreover, eggs laid by homozygous mutant females were fragile, with irregular shapes, and were unable to maintain structural integrity due to eggshell ruptures. However, no significant differences were observed between WT and mutant individuals regarding developmental duration, pupal weight, and mating behavior.

CONCLUSION

Our study suggesteds that PxOsp plays a vital role in female reproduction, particularly in ovary and egg development. Disrupting PxOsp results in recessive female sterility while leaving the male reproductive capability unaffected. This report represents the first study of a haplosufficient gene responsible for female fertility in lepidopteran insects. Additionally, these findings emphasize PxOsp as a potential target for genetically-based pest management of P. xylostella. © 2024 Society of Chemical Industry.

The Set of Serine Peptidases of the Tenebrio molitor Beetle: Transcriptomic Analysis on Different Developmental Stages

Serine peptidases (SPs) of the chymotrypsin S1A subfamily are an extensive group of enzymes found in all animal organisms, including insects. Here, we provide analysis of SPs in the yellow mealworm Tenebrio molitor transcriptomes and genomes datasets and profile their expression patterns at various stages of ontogeny. A total of 269 SPs were identified, including 137 with conserved catalytic triad residues, while 125 others lacking conservation were proposed as non-active serine peptidase homologs (SPHs). Seven deduced sequences exhibit a complex domain organization with two or three peptidase units (domains), predicted both as active or non-active. The largest group of 84 SPs and 102 SPHs had no regulatory domains in the propeptide, and the majority of them were expressed only in the feeding life stages, larvae and adults, presumably playing an important role in digestion. The remaining 53 SPs and 23 SPHs had different regulatory domains, showed constitutive or upregulated expression at eggs or/and pupae stages, participating in regulation of various physiological processes. The majority of polypeptidases were mainly expressed at the pupal and adult stages. The data obtained expand our knowledge on SPs/SPHs and provide the basis for further studies of the functions of proteins from the S1A subfamily in T. molitor.

Altered Gene Expression of the Parasitoid Pteromalus puparum after Entomopathogenic Fungus Beauveria bassiana Infection

Both parasitoids and entomopathogenic fungi are becoming increasingly crucial for managing pest populations. Therefore, it is essential to carefully consider the potential impact of entomopathogenic fungi on parasitoids due to their widespread pathogenicity and the possible overlap between these biological control tools during field applications. However, despite their importance, little research has been conducted on the pathogenicity of entomopathogenic fungi on parasitoids. In our study, we aimed to address this knowledge gap by investigating the interaction between the well-known entomopathogenic fungus Beauveria bassiana, and the pupal endoparasitoid Pteromalus puparum. Our results demonstrated that the presence of B. bassiana significantly affected the survival rates of P. puparum under laboratory conditions. The pathogenicity of B. bassiana on P. puparum was dose- and time-dependent, as determined via through surface spraying or oral ingestion. RNA-Seq analysis revealed that the immune system plays a primary and crucial role in defending against B. bassiana. Notably, several upregulated differentially expressed genes (DEGs) involved in the Toll and IMD pathways, which are key components of the insect immune system, and antimicrobial peptides were rapidly induced during both the early and late stages of infection. In contrast, a majority of genes involved in the activation of prophenoloxidase and antioxidant mechanisms were downregulated. Additionally, we identified downregulated DEGs related to cuticle formation, olfactory mechanisms, and detoxification processes. In summary, our study provides valuable insights into the interactions between P. puparum and B. bassiana, shedding light on the changes in gene expression during fungal infection. These findings have significant implications for the development of more effective and sustainable strategies for pest management in agriculture.

Toll and IMD Immune Pathways Are Important Antifungal Defense Components in a Pupal Parasitoid, Pteromalus puparum

Insects employ multifaceted strategies to combat invading fungi, with immunity being a promising mechanism. Immune pathways function in signal transduction and amplification, ultimately leading to the activation of antimicrobial peptides (AMPs). Although several studies have shown that immune pathways are responsible for defending against fungi, the roles of parasitoid immune pathways involved in antifungal responses remain unknown. In this study, we evaluated the roles of the Toll and IMD pathways of a pupal parasitoid, Pteromalus puparum (Hymenoptera: Pteromalidae), in fighting against Beauveria bassiana (Hypocreales: Cordycipitaceae). Successful colonization of B. bassiana on P. puparum adults was confirmed by scanning electron microscopy (SEM). AMPs were induced upon B. bassiana infection. The knockdown of key genes, PpTollA and PpIMD, in Toll and IMD signaling pathways, respectively, significantly compromised insect defense against fungal infection. The knockdown of either PpTollA or PpIMD in P. puparum dramatically promoted the proliferation of B. bassiana, resulting in a decreased survival rate and downregulated expression levels of AMPs against B. bassiana compared to controls. These data indicated that PpTollA and PpIMD participate in Toll and IMD-mediated activation of antifungal responses, respectively. In summary, this study has greatly broadened our knowledge of the parasitoid antifungal immunity against fungi.

Identification and gene expression analysis of serine proteases and their homologs in the Asian corn borer Ostrinia furnacalis

Serine proteases (SPs) and their homologs (SPHs) are among the best-characterized gene families. They are involved in several physiological processes, including digestion, embryonic development and immunity. In the current study, a total of 177 SPs-related genes were characterized in the genome of Ostrinia furnacalis. The activation site of SPs/SPHs and enzyme specificity of SPs were identified, and the findings showed that most of the SPs analyzed possessed trypsin substrate specificity. Several SPs/SPHs with similar simple gene structures had tandem repeat-like distributions on the scaffold, indicated that gene expansion has occurred in this large family. Furthermore, we constructed 30 RNA sequencing libraries including four with developmental stage and four middle larval stage tissues to study the transcript levels of these genes. Differentially upregulated and downregulated genes were obtained via data analysis. More than one-quarter of the genes were specifically identified as highly expressed in the midgut in compared to the other three tissues evaluated. In the current study, the domain structure, gene location and phylogenetic relationship of genes in O. furnacalis were explored. Orthologous comparisons of SPs/SPHs between model insects and O. furnacalis indicated their possible functions. This information provides a basis for understanding the functional roles of this large family.

Molting-related proteases in the brown planthopper, Nilaparvata lugens

Digestion and absorption of old cuticles during insect molting are necessary for new cuticle formation, during which complicated enzyme catalysis is essential. To date, a few carboxypeptidases, aminopeptidases and serine proteases (mostly trypsins) connected with cuticle digestion, zymogen activation and histological differentiation during the ecdysis of lepidopteran, dipteran and hymenopteran insects have been identified. However, little is known about these proteins in hemimetabolous insects. In this study, we identified 33 candidate trypsin and trypsin-like homologs, 14 metallocarboxypeptidase and 32 aminopeptidase genes in the brown planthopper Nilaparvata lugens, a hemipteran rice pest. Among the proteins encoded by these genes, 9 trypsin-like proteases, 3 metallocarboxypeptidases and 1 aminopeptidase were selected as potential procuticle hydrolases by bioinformatics analysis and in vivo validation. RNA interference targeting these genes demonstrated that 3 trypsin-like proteases (NlTrypsin-8, NlTrypsin-29 and NlTrypsin-32) genes and 1 metallocarboxypeptidase (NlCpB) gene were found to be essential for ecdysis in N. lugens; specifically, gene silencing led to incomplete cuticle degradation and arrested ecdysis, causing lethal morphological phenotype acquisition. Spatiotemporal expression profiling by quantitative PCR and western blotting revealed their specific expression in the integument and their periodic expression during each stadium, with a peak before ecdysis and eclosion. Transmission electron microscopy demonstrated corresponding ultrastructural defects after RNAi targeting, with NlCpB-silenced specimens having the most undigested old procuticles. Immunohistochemical staining revealed that NlTrypsin-8, NlTrypsin-29 and NlCpB were predominantly located in the exuvial space. This research further adds to our understanding of proteases and its potential role in insect ecdysis.

Identification and expression profiling of serine protease-related genes in Tenebrio molitor

In insects, serine proteases and serine protease homologs (SPs/SPHs) are involved in a variety of physiological processes including digestion, development, and immunity. Here, we identified 112 SP and 88 SPH genes in the genome of the yellow mealworm, Tenebrio molitor. Based on the features of domain structure, they were divided into "S" group containing single Tryp-SPc or Tryp-SPHc domain, "C" group containing 1-4 CLIP domain (CLIPA-D) and "M" group containing the CBD, CUB, EGF, Fz, Gd, LDLa, PAN, SEA, SR, Sushi, and TSP domains, and have 115, 48, and 37 gene members, respectively. According to the active sites in the catalytic triad, the putative trypsin, chymotrypsin, or elastase-like enzyme specificity of the identified SPs/SPHs were predicted. Phylogenetic and genomic location analyses revealed that gene duplication exists in the large amount of SPs/SPHs. Gene expression profiling using RNA-seq data along with real time reverse transcription-polymerase chain reaction analysis showed that most SP/SPH genes display life stage specific expression patterns, indicating their important roles in development. Many SP/SPH genes are specifically or highly expressed in the gut, salivary gland, fat body, hemocyte, ovary, and testis, suggesting that they participate in digestion, immunity, and reproduction. The findings lay the foundation for further functional characterization of SPs/SPHs in T. molitor.

The larval saliva of an endoparasitic wasp, Pteromalus puparum, suppresses host immunity

In the lengthy co-evolution between insects and their animal or plant hosts, insects have evolved a wide range of salivary strategies to help evade host defenses. Although there is a very large literature on saliva of herbivorous and hematophagous insects, little attention has been focused on the saliva of parasitoid wasps. Some parasitoid species are natural enemies that effectively regulate insect population sizes in nature that they are applied for biological control of agricultural pests. Here, we demonstrate the influence of the endoparasitoid, Pteromalus puparum, larval saliva on the cellular and humoral immunity of its host. Larval saliva increases mortality of hemocytes, and inhibits hemocyte spreading, a specific cellular immune action. We report that high saliva concentrations inhibit host cellular encapsulation of foreign invaders. The larval saliva also inhibits melanization in host hemolymph. The saliva inhibits the growth of some bacterial species, Bacillus subtilis, Staphylococcus aureus and Pseudomonas aeruginosa in vitro. This may promote larvae fitness by protecting them from infections. Insight into such functions of parasitic wasp saliva provides a new insight into host-parasitoid relationships and possibly leads to new agricultural pest management technologies.

The Micrococcus luteus infection activates a novel melanization pathway of cSP10, cSP4, and cSP8 in Helicoverpa armigera

Melanization is a key immune response mediated by serine protease (SP) cascade in insects. Multiple SP pathways exist in different species and it is unclear how conserved these cascades are. The cotton bollworm Helicoverpa armigera is a major worldwide agricultural pest. We reported a conserved melanization pathway in this species, which consists of SP41, cSP1, and cSP6. In this study, we attempted to identify an insect pathogen that elicits the cascade and test whether or not there are other SP cascades in H. armigera. After Micrococcus luteus, Enterobacter cloacae, Beauveria bassiana, or Helicoverpa armigera nucleopolyhedrovirus were injected into larvae, pathogen-induced hemolymph samples were collected for in vitro biochemical assays, which failed to detect proSP41 or procSP1 activation. In contrast, we found that procSP4, a protein proposed to participate in H. armigera melanization, was activated in M. luteus infected hemolymph. We further revealed that cSP8 was a prophenoloxidase (PPO) activating protease downstream of cSP4, and cSP4 was activated by cSP10. The pathway of cSP10-cSP4-cSP8 activated PPO in vitro. Efficiently cleaved procSPH11 and procSPH50 by cSP8 substantially enhanced phenoloxidase activity, suggesting they work together as a cofactor for cSP8 mediated PPO activation. Hemolymph from larvae challenged with M. luteus or its peptidoglycan effectively activated procSP10. Collectively, these results revealed a new PPO activation cascade specifically triggered by the bacterium. In addition, we found that the PPO activation cascades in H. armigera and Manduca sexta are conserved.

Comprehensive Assessment of Candidate Reference Genes for Gene Expression Studies Using RT-qPCR in Tamarixia radiata, a Predominant Parasitoid of Diaphorina citri

Tamarixia radiata (Waterston) is a predominant parasitoid of the Asian citrus psyllid (ACP), a destructive citrus pest and vector of huanglongbing (HLB) disease in the fields of southern China. To explore the functioning of target genes in T. radiata, the screening of specific reference genes is critical for carrying out the reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) under different experimental conditions. However, no reference gene(s) for T. radiata has yet been reported. Here, we selected seven housekeeping genes of T. radiate and evaluated their stability under the six conditions (developmental stage, sex, tissue, population, temperature, diet) by using RefFinder software, which contains four different programs (geNorm, ΔCt, BestKeeper, and NormFinder). Pairwise variation was analyzed by geNorm software to determine the optimal number of reference genes during the RT-qPCR analysis. The results reveal better reference genes for differing research foci: 18S and EF1A for the developmental stage; PRS18 and EF1A for sex, PRS18 and RPL13 for different tissues (head, thorax, abdomen); EF1A and ArgK between two populations; β-tubulin and EF1A for different temperatures (5, 15, 25, 35 °C); and ArgK and PRS18 for different feeding diets. Furthermore, when the two optimal and two most inappropriate reference genes were chosen in different temperatures and tissue treatments, respectively, the corresponding expression patterns of HSP70 (as the reporter gene) differed substantially. Our study provides, for the first time, a more comprehensive list of optimal reference genes from T. radiata for use in RT-qPCR analysis, which should prove beneficial for subsequent functional investigations of target gene(s) in this natural enemy of ACP.

Venom serine proteinase homolog of the ectoparasitoid Scleroderma guani impairs host phenoloxidase cascade

The ant-like bethylid ectoparasitoid Scleroderma guani (Hymenoptera: Bethylidae) envenomates host to suppress immune response. Yet, the roles of its venom in inhibiting melanization of the host hemolymph have not been fully characterized. Here, we demonstrated that S. guani envenomation induced strong inhibition of melanization of the hemolymph from Tenebrio molitor (Coleoptera: Tenebrionidae), permitting the successful development of parasitoid offspring. To reveal venom component associated with such function, a serine proteinase homolog (SguaSPH) rich in the venom of S. guani was characterized. It was found that one of the catalytic triad residues for serine proteinase is absent in the amino acid sequence of SguaSPH. This venom component was abundantly expressed in venom apparatus and adult stages. By enzymatic assays, SguaSPH displayed low trypsin and no chymotrypsin activity, and was able to inhibit phenoloxidase activity in the hemolymph of Ostrinia furnacalis (Lepidoptera: Crambidae). The findings suggest that SguaSPH is essential for interfering with hemolymph melanization of S. guani envenomated host via phenoloxidase cascade disruption.

Insight into the Functional Diversification of Lipases in the Endoparasitoid Pteromalus puparum (Hymenoptera: Pteromalidae) by Genome-scale Annotation and Expression Analysis

Lipases play essential roles in digestion, transport, and processing of dietary lipids in insects. For parasitoid wasps with a unique life cycle, lipase functions could be multitudinous in particular. Pteromalus puparum is a pupal endoparasitoid of butterflies. The female adult deposits eggs into its host, along with multifunctional venom, and the developing larvae consume host as its main nutrition source. Parasitoid lipases are known to participate in the food digestion process, but the mechanism remains unclear. P. puparum genome and transcriptome data were interrogated. Multiple alignments and phylogenetic trees were constructed. We annotated a total of 64 predicted lipase genes belonging to five lipase families and suggested that eight venom and four salivary lipases could determine host nutrition environment post-parasitization. Many putative venom lipases were found with incomplete catalytic triads, relatively long β9 loops, and short lids. Data analysis reveals the loss of catalytic activities and weak triacylglycerol (TAG) hydrolytic activities of lipases in venom. Phylogenetic trees indicate various predicted functions of lipases in P. puparum. Our information enriches the database of parasitoid lipases and the knowledge of their functional diversification, providing novel insight into how parasitoid wasps manipulate host lipid storage by using venom lipases.

Genome-wide characterization and transcriptomic analyses of neuropeptides and their receptors in an endoparasitoid wasp, Pteromalus puparum

In insects, neuropeptides constitute a group of signaling molecules that act in regulation of multiple physiological and behavioral processes by binding to their corresponding receptors. On the basis of the bioinformatic approaches, we screened the genomic and transcriptomic data of the parasitoid wasp, Pteromalus puparum, and annotated 36 neuropeptide precursor genes and 33 neuropeptide receptor genes. Compared to the number of precursor genes in Bombyx mori (Lepidoptera), Chilo suppressalis (Lepidoptera), Drosophila melanogaster (Diptera), Nilaparvata lugens (Hemiptera), Apis mellifera (Hymenoptera), and Tribolium castaneum (Coleoptera), P. puparum (Hymenoptera) has the lowest number of neuropeptide precursor genes. This lower number may relate to its parasitic life cycle. Transcriptomic data of embryos, larvae, pupae, adults, venom glands, salivary glands, ovaries, and the remaining carcass revealed stage-, sex-, and tissue-specific expression patterns of the neuropeptides, and their receptors. These data provided basic information about the identity and expression profiles of neuropeptides and their receptors that are required to functionally address their biological significance in an endoparasitoid wasp.

Immune signaling pathways in the endoparasitoid, Pteromalus puparum

Parasitoids serve as effective biocontrol agents for agricultural pests. However, they face constant challenges from host immune defense and numerous pathogens and must develop potent immune defense against these threats. Despite the recent advances in innate immunity, little is known about the immunological mechanisms of parasitoids. Here, we identified and characterized potential immune-related genes of the endoparasitoid, Pteromalus puparum, which act in regulating populations of some members of the Pieridae. We identified 216 immune-related genes based on interrogating the P. puparum genome and transcriptome databases. We categorized the cognate gene products into recognition molecules, signal moieties and effector proteins operating in four pathways, Toll, IMD, JAK/STAT, and JNK. Comparative analyses of immune-related genes from seven insect species indicate that recognition molecules and effector proteins are more expanded and diversified than signaling genes in these signal pathways. There are common 1:1 orthologs between the endoparasitoid P. puparum and its relative, the ectoparasitoid Nasonia vitripennis. The developmental expression profiles of immune genes randomly selected from the transcriptome analysis were verified by a quantitative polymerase chain reaction. Our work provides comprehensive analyses of P. puparum immune genes, some of which may be exploited in advancing parasitoid-based biocontrol technologies.

Genomic and transcriptomic analyses of glutathione S-transferases in an endoparasitoid wasp, Pteromalus puparum

Pteromalus puparum is a gregarious pupal endoparasitoid with a wide host range. It deposits eggs into pierid and papilionid butterfly pupae. Glutathione S-transferases (GSTs) are a family of multifunctional detoxification enzymes that act in xenobiotic metabolism in insects. Insect genome projects have facilitated identification and characterization of GST family members. We identified 20 putative GSTs in the P. puparum genome, including 19 cytosolic and one microsomal. Phylogenetic analysis showed that P. puparum GSTs are clustered into Hymenoptera-specific branches. Transcriptomic data of embryos, larvae, female pupae, male pupae, female adults, male adults, venom glands, carcass, salivary glands, and ovaries revealed stage-, sex-, and tissue-specific expression patterns of GSTs in P. puparum. This is the most comprehensive study of genome-wide identification, characterization, and expression profiling of GST family in hymenopterans. Our results provide valuable information for understanding the metabolic adaptation of this wasp.

Genes acting in longevity-related pathways in the endoparasitoid, Pteromalus puparum

Among insects, lifespans vary over a broad range, from the short-lived mayflies to the 17-year periodical cicadas. Generally, lifespans are determined by a phase in life, the reproductive lifespan, which varies among species. Numerous pathways, such as the insulin/insulin-like growth factor signaling pathway, the target of rapamycin pathway and the mitogen-activated protein kinase/extracellular signal-regulated kinases pathways, influence aging and lifespan. Components of these pathways were identified as lifespan-related genes, including genes mediating growth, metabolism, development, resistance, and other processes. Many age-related genes have been discovered in fruit flies, honeybees, and ants among other insect species. Studies of insect aging and longevity can help understand insect biology and develop new pest management technologies. In this paper, we interrogated the new Pteromalus puparum genome, from which we predicted 133 putative lifespan-related genes based on their homology with known lifespan-related genes of Drosophila melanogaster. These genes function in five signaling pathways and three physiological processes. The conserved domain structures of these genes were predicted and their expression patterns were analyzed. Amino acid sequence alignments and domain structure analysis indicate that most components remain conserved across at least six insect orders. The data in this paper will facilitate future work on parasitoid lifespans, which may have economic value in biocontrol programs.

Clip-Domain Serine Protease Gene (LsCLIP3) Is Essential for Larval-Pupal Molting and Immunity in Lasioderma serricorne

Clip-domain serine proteases (CLIPs) play crucial roles in insect development and innate immunity. In this study, we identified a CLIP gene (designated LsCLIP3) from the cigarette beetle Lasioderma serricorne. LsCLIP3 contains a 1,773-bp open reading frame (ORF) encoding a 390-amino-acid protein and shows a conserved clip domain and a trypsin-like serine protease domain. Phylogenetic analysis indicated that LsCLIP3 was orthologous to the CLIP-B subfamily. LsCLIP3 was prominently expressed in larva, pupa, and early adult stages. In larval tissues, it was highly expressed in the integument and fat body. The expression of LsCLIP3 was induced by 20-hydroxyecdysone. A similar induction was also found by peptidoglycans from Escherichia coli and Staphylococcus aureus. RNA interference (RNAi)-mediated silencing of LsCLIP3 disrupted larval–pupal molting and specifically reduced the expression of genes in 20-hydroxyecdysone synthesis and signaling pathway. The chitin amounts of LsCLIP3 RNAi larvae were greatly decreased, and expressions of six chitin metabolic-related genes were significantly reduced. Knockdown of LsCLIP3 increased larval sensitivity to Gram-negative and Gram-positive bacteria. There was significantly decreased expression of four antimicrobial peptide (AMP) genes. The results suggest that LsCLIP3 is an important component of the larva to pupa molt and for the immunity of L. serricorne.

Identification and Comparative Analysis of Venom Proteins in a Pupal Ectoparasitoid, Pachycrepoideus vindemmiae

Parasitoid wasps inject venom containing complex bioactive compounds to regulate the immune response and development of host arthropods and sometime paralyze host arthropods. Although extensive studies have been conducted on the identification of venom proteins in larval parasitoids, relatively few studies have examined the pupal parasitoids. In our current study, a combination of transcriptomic and proteomic methods was used to identify 64 putative venom proteins from Pachycrepoideus vindemmiae, an ectoparasitoid of Drosophila. Expression analysis revealed that 20 tested venom proteins have 419-fold higher mean expression in the venom apparatus than in other wasp tissues, indicating their specialization to venom. Comparisons of venom proteins from P. vindemmiae and other five species spanning three parasitoid families detected a core set of "ancient" orthologs in Pteromalidae. Thirty-five venom proteins of P. vindemmiae were assigned to the orthologous groups by reciprocal best matches with venoms of other pteromalids, while the remaining 29 were not. Of the 35 categories, twenty-seven have orthologous relationships with Nasonia vitripennis venom proteins and 25 with venoms of Pteromalus puparum. More distant relationships detected that five and two venom proteins of P. vindemmiae are orthologous with venoms of two Figitidae parasitoids and a Braconidae representative, respectively. Moreover, twenty-two venoms unique to P. vindemmiae were also detected, indicating considerable interspecific variation of venom proteins in parasitoids. Phylogenetic reconstruction based on a set of single-copy genes clustered P. vindemmiae with P. puparum, N. vitripennis, and other members of the family Pteromalidae. These findings provide strong evidence that P. vindemmiae venom proteins are well positioned for future functional and evolutionary studies.

Insights into the venom protein components of Microplitis mediator, an endoparasitoid wasp

Endoparasitoid wasps deliver a variety of maternal factors, such as venom proteins, viruses, and virus-like particles, from their venom and calyx fluid into hosts and thereby regulate the hosts' immune response, metabolism and development. The endoparasitoid, Microplitis mediator, is used as an important biological agent for controlling the devastating pest Helicoverpa armigera. In this study, using an integrated transcriptomic and proteomic analysis approach, we identified 75 putative venom proteins in M. mediator. The identified venom components were consistent with other known parasitoid wasps' venom proteins, including metalloproteases, serine protease inhibitors, and glycoside hydrolase family 18 enzymes. The metalloprotease and serpin family showed extensive gene duplications in venom apparatus. Isobaric tags for relative and absolute quantitation (iTRAQ) based quantitative proteomics revealed 521 proteins that were differentially expressed at 6 h and 24 h post-parasitism, including 10 wasp venom proteins that were released into the host hemolymph. Further analysis indicated that 511 differentially expressed proteins (DEP) from the host are primarily involved in the immune response, material metabolism, and extracellular matrix receptor interaction. Taken together, our results on parasitoid wasp venoms have the potential to enhance the application of endoparasitoid wasps for controlling insect pest.

Identification and characterization of serine protease inhibitors in a parasitic wasp, Pteromalus puparum

Serine protease inhibitors (SPIs) regulate protease-mediated activities by inactivating their cognate proteinases, and are involved in multiple physiological processes. SPIs have been extensively studied in vertebrates and invertebrates; however, little SPI information is available in parasitoids. Herein, we identified 57 SPI genes in total through the genome of a parasitoid wasp, Pteromalus puparum. Gene structure analyses revealed that these SPIs contain 7 SPI domains. Depending on their mode of action, these SPIs can be categorized into serpins, canonical inhibitors and alpha-2-macroglobulins (A2Ms). For serpins and canonical inhibitors, we predicted their putative inhibitory activities to trypsin/chymotrypsin/elastase-like enzymes based on the amino acids in cleaved reactive sites. Sequence alignment and phylogenetic tree indicated that some serpins similar to known functional inhibitory serpins may participate in immune responses. Transcriptome analysis also showed some canonical SPI genes displayed distinct expression patterns in the venom gland and this was confirmed by quantitative real-time PCR (qPCR) analysis, suggesting their specific physiological functions as venom proteins in suppressing host immune responses. The study provides valuable information to clarify the functions of SPIs in digestion, development, reproduction and innate immunity.