A Mutualistic Poxvirus Exhibits Convergent Evolution with Other Heritable Viruses in Parasitoid Wasps

Host range of a parasitoid wasp is linked to host susceptibility to its mutualistic viral symbiont

Parasitoid wasps are one of the most species-rich groups of animals on Earth, due to their ability to successfully develop as parasites of nearly all types of insects. Unlike most known parasitoid wasps that specialize towards one or a few host species, Diachasmimorpha longicaudata is a generalist that can survive within multiple genera of tephritid fruit fly hosts, including many globally important pest species. Diachasmimorpha longicaudata has therefore been widely released to suppress pest populations as part of biological control efforts in tropical and subtropical agricultural ecosystems. In this study, we investigated the role of a mutualistic poxvirus in shaping the host range of D. longicaudata across three genera of agricultural pest species: two of which are permissive hosts for D. longicaudata parasitism and one that is a nonpermissive host. We found that permissive hosts Ceratitis capitata and Bactrocera dorsalis were highly susceptible to manual virus injection, displaying rapid virus replication and abundant fly mortality. However, the nonpermissive host Zeugodacus cucurbitae largely overcame virus infection, exhibiting substantially lower mortality and no virus replication. Investigation of transcriptional dynamics during virus infection demonstrated hindered viral gene expression and limited changes in fly gene expression within the nonpermissive host compared with the permissive species, indicating that the host range of the viral symbiont may influence the host range of D. longicaudata wasps. These findings also reveal that viral symbiont activity may be a major contributor to the success of D. longicaudata as a generalist parasitoid species and a globally successful biological control agent.

Rich diversity of RNA viruses in the biological control agent, Orius laevigatus

Orius laevigatus (Hemiptera, Anthocoridae) is a generalist predator extensively used for the biocontrol of diverse agricultural pests. Previous studies on O. laevigatus have focused on the improvement of insect genetic traits, but little is known about its association with microbes, especially viruses that may influence its production and efficacy. More than 280 RNA viruses have been described in other Hemiptera insects, in line with the continuous discovery of insect-specific viruses (ISVs) boosted by next-generation sequencing. In this study, we characterized the repertoire of RNA viruses associated with O. laevigatus. Its virome comprises 27 RNA viruses, classified within fourteen viral families, of which twenty-three viruses are specific to O. laevigatus and four are likely associated with fungal microbiota. The analysis of viral abundance in five O. laevigatus populations confirmed the presence of simultaneous viral infections and highlighted the ubiquitous presence and high abundance of one solinvivirus and three totiviruses. Moreover, we identified 24 non-retroviral endogenous viral elements (nrEVEs) in the genome of O. laevigatus, suggesting a long-term relationship between the host and its virome. Although no symptoms were described in the insect populations under study, the high diversity of viral species and the high abundance of certain RNA viruses identified indicate that RNA viruses may be significant for the applicability and efficacy of O. laevigatus in biocontrol programs.

Shaping the Microbial Landscape: Parasitoid-Driven Modifications of Bactrocera dorsalis Microbiota

Koinobiont endoparasitoids regulate the physiology of their hosts through altering host immuno-metabolic responses, processes which function in tandem to shape the composition of the microbiota of these hosts. Here, we employed 16S rRNA and ITS amplicon sequencing to investigate whether parasitization by the parasitoid wasps, Diachasmimorpha longicaudata (Ashmaed) (Hymenoptera: Braconidae) and Psyttalia cosyrae (Wilkinson) (Hymenoptera: Braconidae), induces gut dysbiosis and differentially alter the gut microbial (bacteria and fungi) communities of an important horticultural pest, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). We further investigated the composition of bacterial communities of adult D. longicaudata and P. cosyrae to ascertain whether the adult parasitoids and parasitized host larvae share microbial taxa through transmission. We demonstrated that parasitism by D. longicaudata induced significant gut perturbations, resulting in the colonization and increased relative abundance of pathogenic gut bacteria. Some pathogenic bacteria like Stenotrophomonas and Morganella were detected in both the guts of D. longicaudata-parasitized B. dorsalis larvae and adult D. longicaudata wasps, suggesting a horizontal transfer of microbes from the parasitoid to the host. The bacterial community of P. cosyrae adult wasps was dominated by Arsenophonus nasoniae, whereas that of D. longicaudata adults was dominated by Paucibater spp. and Pseudomonas spp. Parasitization by either parasitoid wasp was associated with an overall reduction in fungal diversity and evenness. These findings indicate that unlike P. cosyrae which is avirulent to B. dorsalis, parasitization by D. longicaudata induces shifts in the gut bacteriome of B. dorsalis larvae to a pathobiont-dominated community. This mechanism possibly enhances its virulence against the pest, further supporting its candidacy as an effective biocontrol agent of this frugivorous tephritid fruit fly pest.

Naturally occurring viruses of Drosophila reduce offspring number and lifespan

Drosophila remains a pre-eminent insect model system for host-virus interaction, but the host range and fitness consequences of the drosophilid virome are poorly understood. Metagenomic studies have reported approximately 200 viruses associated with Drosophilidae, but few isolates are available to characterize the Drosophila immune response, and most characterization has relied on injection and systemic infection. Here, we use a more natural infection route to characterize the fitness effects of infection and to study a wider range of viruses. We exposed laboratory Drosophila melanogaster to 23 naturally occurring viruses from wild-collected drosophilids. We recorded transmission rates along with two components of female fitness: survival and the lifetime number of adult offspring produced. Nine different viruses transmitted during contact with laboratory D. melanogaster, although for the majority, rates of transmission were less than 20%. Five virus infections led to a significant decrease in lifespan (D. melanogaster Nora virus, D. immigrans Nora virus, Muthill virus, galbut virus and Prestney Burn virus), and three led to a reduction in the total number of offspring. Our findings demonstrate the utility of the Drosophila model for community-level studies of host-virus interactions, and suggest that viral infection could be a substantial fitness burden on wild flies.

The Viromes of Six Ecosystem Service Provider Parasitoid Wasps

Parasitoid wasps are fundamental insects for the biological control of agricultural pests. Despite the importance of wasps as natural enemies for more sustainable and healthy agriculture, the factors that could impact their species richness, abundance, and fitness, such as viral diseases, remain almost unexplored. Parasitoid wasps have been studied with regard to the endogenization of viral elements and the transmission of endogenous viral proteins that facilitate parasitism. However, circulating viruses are poorly characterized. Here, RNA viromes of six parasitoid wasp species are studied using public libraries of next-generation sequencing through an integrative bioinformatics pipeline. Our analyses led to the identification of 18 viruses classified into 10 families (Iflaviridae, Endornaviridae, Mitoviridae, Partitiviridae, Virgaviridae, Rhabdoviridae, Chuviridae, Orthomyxoviridae, Xinmoviridae, and Narnaviridae) and into the Bunyavirales order. Of these, 16 elements were described for the first time. We also found a known virus previously identified on a wasp prey which suggests viral transmission between the insects. Altogether, our results highlight the importance of virus surveillance in wasps as its service disruption can affect ecology, agriculture and pest management, impacting the economy and threatening human food security.

RNA virus diversity in three parasitoid wasps of tephritid flies: insights from novel and known species

IMPORTANCE

Parasitoid wasp populations have developed persistent beneficial symbiotic relationships with several viruses through repeated evolution. However, there have been limited reports on RNA viruses in parasitoid wasps of tephritid flies, a significant pest group affecting fruits and vegetables. This study explores the diversity of RNA viruses in three parasitoid wasps of tephritid flies and highlights the potential biological significance of specific viruses in Diachasmimorpha longicaudata. These findings have important implications for the development of sustainable pest management strategies and the enhancement of artificial rearing techniques for parasitoid wasps.

RNA Viruses Are Prevalent and Active Tenants of the Predatory Mite Phytoseiulus persimilis (Acari: Phytoseiidae)

Many arthropod species harbor a diverse range of viruses. While much is known about pathogenic viruses of some economically important insects and arthropods involved in disease transmission, viruses associated with mites have rarely been studied. The main objective of this study was to characterize the virome of Phytoseiulus persimilis (Phytoseiidae), a predatory mite commercially used worldwide for the biological control of the key pest Tetranychus urticae (Tetranichidae). A combination of de novo transcriptome assembly and virion sequencing, revealed that RNA viruses are highly prevalent and active tenants of commercial populations of P. persimilis, comprising on average 9% of the mite's total mRNA. Seventeen RNA viruses dominated the mite's virome (i.e., were highly transcribed) with over half (n = 10) belonging to the order Picornavirales, + ssRNA viruses that infect a large range of hosts, including arthropods. Screening of the 17 dominant virus sequences in P. persimilis and T. urticae revealed that three viruses (two Picornavirales of the families Iflaviridae and Dicistroviridae, and one unclassified Riboviria) are unique to P. persimilis and three others (two unclassified Picornavirales and one unclassified Riboviria) are present in both mite species. Most of the sequences were related to viruses previously documented in economically important arthropods, while others have rarely been documented before in arthropods. These findings demonstrate that P. persimilis, like many other arthropods, harbors a diverse RNA virome, which might affect the mite's physiology and consequently its efficiency as a biological control agent.

Genomic characterization of viruses associated with the parasitoid Anagyrus vladimiri (Hymenoptera: Encyrtidae)

Knowledge on symbiotic microorganisms of insects has increased dramatically in recent years, yet relatively little data are available regarding non-pathogenic viruses. Here we studied the virome of the parasitoid wasp Anagyrus vladimiri Triapitsyn (Hymenoptera: Encyrtidae), a biocontrol agent of mealybugs. By high-throughput sequencing of viral nucleic acids, we revealed three novel viruses, belonging to the families Reoviridae [provisionally termed AnvRV (Anagyrus vladimiri reovirus)], Iflaviridae (AnvIFV) and Dicistroviridae (AnvDV). Phylogenetic analysis further classified AnvRV in the genus Idnoreovirus, and AnvDV in the genus Triatovirus. The genome of AnvRV comprises 10 distinct genomic segments ranging in length from 1.5 to 4.2 kb, but only two out of the 10 ORFs have a known function. AnvIFV and AnvDV each have one polypeptide ORF, which is typical of iflaviruses but very un-common among dicistroviruses. Five conserved domains were found along both the ORFs of those two viruses. AnvRV was found to be fixed in an A. vladimiri population that was obtained from a mass rearing facility, whereas its prevalence in field-collected A. vladimiri was ~15 %. Similarly, the prevalence of AnvIFV and AnvDV was much higher in the mass rearing population than in the field population. The presence of AnvDV was positively correlated with the presence of Wolbachia in the same individuals. Transmission electron micrographs of females' ovaries revealed clusters and viroplasms of reovirus-like particles in follicle cells, suggesting that AnvRV is vertically transmitted from mother to offspring. AnvRV was not detected in the mealybugs, supporting the assumption that this virus is truly associated with the wasps. The possible effects of these viruses on A. vladimiri's biology, and on biocontrol agents in general, are discussed. Our findings identify RNA viruses as potentially involved in the multitrophic system of mealybugs, their parasitoids and other members of the holobiont.

Mining Amphibian and Insect Transcriptomes for Antimicrobial Peptide Sequences with rAMPage

Antibiotic resistance is a global health crisis increasing in prevalence every day. To combat this crisis, alternative antimicrobial therapeutics are urgently needed. Antimicrobial peptides (AMPs), a family of short defense proteins, are produced naturally by all organisms and hold great potential as effective alternatives to small molecule antibiotics. Here, we present rAMPage, a scalable bioinformatics discovery platform for identifying AMP sequences from RNA sequencing (RNA-seq) datasets. In our study, we demonstrate the utility and scalability of rAMPage, running it on 84 publicly available RNA-seq datasets from 75 amphibian and insect species—species known to have rich AMP repertoires. Across these datasets, we identified 1137 putative AMPs, 1024 of which were deemed novel by a homology search in cataloged AMPs in public databases. We selected 21 peptide sequences from this set for antimicrobial susceptibility testing against Escherichia coli and Staphylococcus aureus and observed that seven of them have high antimicrobial activity. Our study illustrates how in silico methods such as rAMPage can enable the fast and efficient discovery of novel antimicrobial peptides as an effective first step in the strenuous process of antimicrobial drug development.

A viral mutualist employs posthatch transmission for vertical and horizontal spread among parasitoid wasps

Mutualistic viruses remain a rarity among known animal–microbe symbioses. Yet, several beneficial viruses have been identified within insects called parasitoid wasps. Most of these viral entities are permanent components of wasp genomes. However, a mutualistic poxvirus found within Diachasmimorpha longicaudata wasps maintains an independent genome and may therefore behave in ways more similar to cellular microbial symbionts. In this study, we discovered unique properties of viral symbiont transmission, including an evolved dependence on parasitoid wasps for virus spread among fruit fly hosts and a distinct mode of faithful virus transmission among parasitoid wasps. These findings demonstrate that certain symbiont transmission pathways have arisen independently across disparate life forms to play pivotal roles in insect biology and evolution.

Heritable symbionts display a wide variety of transmission strategies to travel from one insect generation to the next. Parasitoid wasps, one of the most diverse insect groups, maintain several heritable associations with viruses that are beneficial for wasp survival during their development as parasites of other insects. Most of these beneficial viral entities are strictly transmitted through the wasp germline as endogenous viral elements within wasp genomes. However, a beneficial poxvirus inherited by Diachasmimorpha longicaudata wasps, known as Diachasmimorpha longicaudata entomopoxvirus (DlEPV), is not integrated into the wasp genome and therefore may employ different tactics to infect future wasp generations. Here, we demonstrated that transmission of DlEPV is primarily dependent on parasitoid wasps, since viral transmission within fruit fly hosts of the wasps was limited to injection of the virus directly into the larval fly body cavity. Additionally, we uncovered a previously undocumented form of posthatch transmission for a mutualistic virus that entails external acquisition and localization of the virus within the adult wasp venom gland. We showed that this route is extremely effective for vertical and horizontal transmission of the virus within D. longicaudata wasps. Furthermore, the beneficial phenotype provided by DlEPV during parasitism was also transmitted with perfect efficiency, indicating an effective mode of symbiont spread to the advantage of infected wasps. These results provide insight into the transmission of beneficial viruses among insects and indicate that viruses can share features with cellular microbes during their evolutionary transitions into symbionts.

Many evolutionary roads led to virus domestication in ichneumonoid parasitoid wasps

The investigation of endogenous viral elements (EVEs) has historically focused on only a few lineages of parasitoid wasps, with negative results consistently underreported. Recent studies show that multiple viral lineages were integrated in at least seven instances in Ichneumonoidea and may be much more widespread than previously thought. Increasingly affordable genomic and bioinformatic approaches have made it feasible to search for viral sequences within wasp genomes, opening an extremely promising research avenue. Advances in wasp phylogenetics have shed light on the evolutionary history of EVE integration, although many questions remain. Phylogenetic proximity can be used as a guide to facilitate targeted screening, to estimate the number and age of integration events and to identify taxa involved in major host switches.

Evolution and Diversity of Inherited Viruses in the Nearctic Phantom Midge, Chaoborus americanus

Inherited mutualists, parasites, and commensals occupy one of the most intimate ecological niches available to invertebrate-associated microbes. How this transmission environment influences microbial evolution is increasingly understood for inherited bacterial symbionts, but in viruses, research on the prevalence of vertical transmission and its effects on viral lineages is still maturing. The evolutionary stability of this strategy remains difficult to assess, although phylogenetic evidence of frequent host shifts and selective sweeps have been interpreted as strategies favoring parasite persistence. In this study, we describe and investigate a natural insect system in which species-wide sweeps have been restricted by the isolation of host populations. Previous work identified evidence of pronounced mitochondrial genetic structure among North American populations of the phantom midge, Chaoborus americanus. Here we take advantage of the geographical isolation in this species to investigate the diversity and persistence of its inherited virome. We identify eight novel RNA viruses from six families and use small RNA sequencing in reproductive tissues to provide evidence of vertical transmission. We report region-specific virus strains that mirror the continental phylogeography of the host, demonstrating that members of the inherited virome have independently persisted in parallel host lineages since they last shared a common ancestor in the Mid Pleistocene. We find that the small interfering RNA pathway, a frontline of antiviral defense in insects, targets members of this inherited virome. Finally, our results suggest that the Piwi-mediated RNA silencing pathway is unlikely to function as a general antiviral defense in Chaoborus, in contrast to its role in some mosquitoes. However, we also report that the PIWI-interacting RNA pathway generates abundant piRNAs from endogenous viral elements closely related to actively infecting inherited viruses, potentially helping to explain idiosyncratic patterns of virus-specific Piwi targeting in this insect.

A novel cripavirus of an ectoparasitoid wasp increases pupal duration and fecundity of the wasp's Drosophila melanogaster host

We identified a 9332-nucleotide-long novel picornaviral genome sequence in the transcriptome of an agriculturally important parasitoid wasp (Pachycrepoideus vindemmiae (Rondani, 1875)). The genome of the novel virus, Rondani's wasp virus 1 (RoWV-1), contains two long open reading frames encoding a nonstructural and a structural protein, respectively, and is 3'-polyadenylated. Phylogenetic analyses firmly place RoWV-1 into the dicistrovirid genus Cripavirus. We detected RoWV-1 in various tissues and life stages of the parasitoid wasp, with the highest virus load measured in the larval digestive tract. We demonstrate that RoWV-1 is transmitted horizontally from infected to uninfected wasps but not vertically to wasp offspring. Comparison of several important biological parameters between the infected and uninfected wasps indicates that RoWV-1 does not have obvious detrimental effects on wasps. We further demonstrate that RoWV-1 also infects Drosophila melanogaster (Meigen, 1830), the hosts of the pupal ectoparasitoid wasps, and thereby increases its pupal developmental duration and fecundity, but decreases the eclosion rate. Together, these results suggest that RoWV-1 may have a potential benefit to the wasp by increasing not only the number of potential wasp hosts but also the developmental time of the hosts to ensure proper development of wasp offspring.

Symbiotic Interactions Between Mosquitoes and Mosquito Viruses

Mosquitoes not only transmit human and veterinary pathogens called arboviruses (arthropod-borne viruses) but also harbor mosquito-associated insect-specific viruses (mosquito viruses) that cannot infect vertebrates. In the past, studies investigating mosquito viruses mainly focused on highly pathogenic interactions that were easier to detect than those without visible symptoms. However, the recent advances in viral metagenomics have highlighted the abundance and diversity of viruses which do not generate mass mortality in host populations. Over the last decade, this has facilitated the rapid growth of virus discovery in mosquitoes. The circumstances around the discovery of mosquito viruses greatly affected how they have been studied so far. While earlier research mainly focused on the pathogenesis caused by DNA and some double-stranded RNA viruses during larval stages, more recently discovered single-stranded RNA mosquito viruses were heavily studied for their putative interference with arboviruses in female adults. Thus, many aspects of mosquito virus interactions with their hosts and host-microbiota are still unknown. In this context, considering mosquito viruses as endosymbionts can help to identify novel research areas, in particular in relation to their long-term interactions with their hosts (e.g. relationships during all life stages, the stability of the associations at evolutionary scales, transmission routes and virulence evolution) and the possible context-dependent range of interactions (i.e. beneficial to antagonistic). Here, we review the symbiotic interactions of mosquito viruses considering different aspects of their ecology, such as transmission, host specificity, host immune system and interactions with other symbionts within the host cellular arena. Finally, we highlight related research gaps in mosquito virus research.

The Presence of Ancient Core Genes Reveals Endogenization from Diverse Viral Ancestors in Parasitoid Wasps

The Ichneumonoidea (Ichneumonidae and Braconidae) is an incredibly diverse superfamily of parasitoid wasps that includes species that produce virus-like entities in their reproductive tracts to promote successful parasitism of host insects. Research on these entities has traditionally focused upon two viral genera Bracovirus (in Braconidae) and Ichnovirus (in Ichneumonidae). These viruses are produced using genes known collectively as endogenous viral elements (EVEs) that represent historical, now heritable viral integration events in wasp genomes. Here, new genome sequence assemblies for 11 species and 6 publicly available genomes from the Ichneumonoidea were screened with the goal of identifying novel EVEs and characterizing the breadth of species in lineages with known EVEs. Exhaustive similarity searches combined with the identification of ancient core genes revealed sequences from both known and novel EVEs. One species harbored a novel, independently derived EVE related to a divergent large double-stranded DNA (dsDNA) virus that manipulates behavior in other hymenopteran species. Although bracovirus or ichnovirus EVEs were identified as expected in three species, the absence of ichnoviruses in several species suggests that they are independently derived and present in two younger, less widespread lineages than previously thought. Overall, this study presents a novel bioinformatic approach for EVE discovery in genomes and shows that three divergent virus families (nudiviruses, the ancestors of ichnoviruses, and Leptopilina boulardi Filamentous Virus-like viruses) are recurrently acquired as EVEs in parasitoid wasps. Virus acquisition in the parasitoid wasps is a common process that has occurred in many more than two lineages from a diverse range of arthropod-infecting dsDNA viruses.

Influence of parasitoid-associated viral symbionts on plant-insect interactions and biological control

Insect parasitoids have evolved symbiotic interactions with several viruses and thousands of parasitoid species have established mutualistic associations with polydnaviruses (PDVs). While PDVs have often been described as virulence factors allowing development of immature parasitoids inside their herbivore hosts, there is increasing awareness that PDVs can affect plant-insect interactions. We review recent literature showing that PDVs alter not only host physiology, but also feeding patterns and composition of herbivore's oral secretions. In turn PDV-induced changes in herbivore phenotype affect plant responses to herbivory with consequences ranging from differential expression of plant defense-related genes to wider ecological effects across multiple trophic levels. In this opinion paper we also highlight important missing gaps to fully understand the role of PDVs and other parasitoid-associated viral symbionts in a plant-insect interaction perspective. Because PDVs negatively impact performance and survival of herbivore pests, we conclude arguing that PDV genomes offer potential opportunities for biological control.

MdBVe46 is an envelope protein that is required for virion formation by Microplitis demolitor bracovirus

Bracoviruses (BVs) are endogenized nudiviruses that braconid parasitoid wasps have coopted for functions in parasitizing hosts. Microplitis demolitor is a braconid wasp that produces Microplitis demolitor bracovirus (MdBV) and parasitizes the larval stage of the moth Chrysodeixis includens. Some BV core genes are homologs of genes also present in baculoviruses while others are only known from nudiviruses or other BVs. In this study, we had two main goals. The first was to separate MdBV virions into envelope and nucleocapsid fractions before proteomic analysis to identify core gene products that were preferentially associated with one fraction or the other. Results indicated that nearly all MdBV baculovirus-like gene products that were detected by our proteomic analysis had similar distributions to homologs in the occlusion-derived form of baculoviruses. Several core gene products unknown from baculoviruses were also identified as envelope or nucleocapsid components. Our second goal was to functionally characterize a core gene unknown from baculoviruses that was originally named HzNVorf64-like. Immunoblotting assays supported our proteomic data that identified HzNVorf64-like as an envelope protein. We thus renamed HzNVorf64-like as MdBVe46, which we further hypothesized was important for infection of C. includens. Knockdown of MdBVe46 by RNA interference (RNAi) greatly reduced transcript and protein abundance. Knockdown of MdBVe46 also altered virion morphogenesis, near-fully inhibited infection of C. includens, and significantly reduced the proportion of hosts that were successfully parasitized by M. demolitor.

Review of Venoms of Non-Polydnavirus Carrying Ichneumonoid Wasps

Parasitoids are predominantly insects that develop as larvae on or inside their host, also usually another insect, ultimately killing it after various periods of parasitism when both parasitoid larva and host are alive. The very large wasp superfamily Ichneumonoidea is composed of parasitoids of other insects and comprises a minimum of 100,000 species. The superfamily is dominated by two similarly sized families, Braconidae and Ichneumonidae, which are collectively divided into approximately 80 subfamilies. Of these, six have been shown to release DNA-containing virus-like particles, encoded within the wasp genome, classified in the virus family Polydnaviridae. Polydnaviruses infect and have profound effects on host physiology in conjunction with various venom and ovarial secretions, and have attracted an immense amount of research interest. Physiological interactions between the remaining ichneumonoids and their hosts result from adult venom gland secretions and in some cases, ovarian or larval secretions. Here we review the literature on the relatively few studies on the effects and chemistry of these ichneumonoid venoms and make suggestions for interesting future research areas. In particular, we highlight relatively or potentially easily culturable systems with features largely lacking in currently studied systems and whose study may lead to new insights into the roles of venom chemistry in host-parasitoid relationships as well as their evolution.

Genomic analysis reveals an exogenous viral symbiont with dual functionality in parasitoid wasps and their hosts

Insects are known to host a wide variety of beneficial microbes that are fundamental to many aspects of their biology and have substantially shaped their evolution. Notably, parasitoid wasps have repeatedly evolved beneficial associations with viruses that enable developing wasps to survive as parasites that feed from other insects. Ongoing genomic sequencing efforts have revealed that most of these virus-derived entities are fully integrated into the genomes of parasitoid wasp lineages, representing endogenous viral elements (EVEs) that retain the ability to produce virus or virus-like particles within wasp reproductive tissues. All documented parasitoid EVEs have undergone similar genomic rearrangements compared to their viral ancestors characterized by viral genes scattered across wasp genomes and specific viral gene losses. The recurrent presence of viral endogenization and genomic reorganization in beneficial virus systems identified to date suggest that these features are crucial to forming heritable alliances between parasitoid wasps and viruses. Here, our genomic characterization of a mutualistic poxvirus associated with the wasp Diachasmimorpha longicaudata, known as Diachasmimorpha longicaudata entomopoxvirus (DlEPV), has uncovered the first instance of beneficial virus evolution that does not conform to the genomic architecture shared by parasitoid EVEs with which it displays evolutionary convergence. Rather, DlEPV retains the exogenous viral genome of its poxvirus ancestor and the majority of conserved poxvirus core genes. Additional comparative analyses indicate that DlEPV is related to a fly pathogen and contains a novel gene expansion that may be adaptive to its symbiotic role. Finally, differential expression analysis during virus replication in wasps and fly hosts demonstrates a unique mechanism of functional partitioning that allows DlEPV to persist within and provide benefit to its parasitoid wasp host.