Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Polydnaviridae”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed2006

The few virus-like genes of Cotesia congregata bracovirus.

The origin of the symbiotic association between parasitoid wasps and bracoviruses is still unknown. From phylogenetic analyses, bracovirus-associated wasp species constitute a monophyletic group, the microgastroid complex. Thus all wasp-bracovirus associations could have originated from the integration of an ancestral virus in the genome of the ancestor of the microgastroids. In an effort to identify a set of virus genes that would give clues on the nature of the ancestral virus, we have recently performed the complete sequencing of the genome of CcBV, the bracovirus of the wasp Cotesia congregata. We describe here the putative proteins encoded by CcBV genome having significant similarities with sequences from known viruses and mobile elements. The analysis of CcBV gene content does not lend support to the hypothesis that bracoviruses originated from a baculovirus. Moreover, no consistent homology was found between CcBV genes and any set of genes constituting the core genome of a known free-living virus. We discuss the significance of the scarce homology found between proteins from CcBV and other viruses or mobile elements.

Amino Acid Sequence↗
PubMed2006

Venom proteins from polydnavirus-producing endoparasitoids: their role in host-parasite interactions.

Endoparasitoid wasps have evolved various mechanisms to ensure successful development of their progeny, including co-injection of a cocktail of maternal secretions into the host hemocoel, including venom, calyx fluid, and polydnaviruses. The components of each type of secretion may influence host physiology and development independently or in a synergistic fashion. For example, venom fluid consists of several peptides and proteins that promote expression of polydnavirus genes in addition to other activities, such as inhibition of prophenoloxidase activation, inhibition of hemocytes spreading and aggregation, and inhibition of development. This review provides a brief overview of advances and prospects in the study of venom proteins from polydnavirus-producing endoparasitoid wasps with a special emphasis on the role of C. rubecula venom proteins in host-parasitoid interactions.

Animals↗
PubMed2005

Are insect immune suppressors driving cellular uptake reactions?

Many insect parasitoids that deposit their eggs inside immature stages of other insect species inactivate the cellular host defence to protect the growing embryo from encapsulation. Suppression of encapsulation by polydnavirus-encoded immune-suppressors correlates with specific alterations in hemocytes, mainly cytoskeletal rearrangements and actin-cytoskeleton breakdown. We have previously shown that the Cotesia rubecula polydnavirus gene product CrV1 causes immune suppression when injected into the host hemocoel. CrV1 is taken up by hemocytes although no receptors have been found to bind the protein. Instead CrV1 uptake depends on dimer formation, which is required for interacting with lipophorin, suggesting a CrV1-lipophorin complex internalisation by hemocytes. Since treatment of hemocytes with oligomeric lectins and cytochalasin D can mimic the effects of CrV1, we propose that some dimeric and oligomeric adhesion molecules are able to cross-link receptors on the cell surface and depolymerise actin by leverage-mediated clearance reactions in the hemolymph.

Actins↗
PubMed2006

Protein tyrosine phosphatases of Toxoneuron nigriceps bracovirus as potential disrupters of host prothoracic gland function.

The genomic sequence of the bracovirus associated with the wasp Toxoneuron nigriceps (Hymenoptera, Braconidae) (TnBV), an endophagous parasitoid of the tobacco budworm larvae, Heliothis virescens (Lepidoptera, Noctuidae), contains a large gene family coding for protein tyrosine phosphatases (PTPs). Here we report the characterization of cDNAs for two of the viral PTPs isolated by screening a cDNA library from haemocytes of parasitized host larvae. The two encoded proteins show 70% amino acid identity and are expressed in the fat body of parasitized hosts. In addition, one was expressed in inactivated prothoracic glands (PTGs), 24 h after parasitoid oviposition. The rapid block of ecdysteroidogenesis does not appear to be due to inhibition of general protein synthesis, as indirectly indicated by the unaltered S6 kinase activity in the cytosolic extracts of basal PTGs from parasitized host larvae. Rather, TnBV PTP over-expression in inactivated host PTGs suggests that gland function may be affected by the disruption of the phosphorylation balance of key proteins regulating points upstream from the ribosomal S6 phosphorylation in the PTTH signaling cascade.

Amino Acid Sequence↗
PubMed1994

Isomeric and quaternary properties of homogenous 33 kDa protein from the venom of Chelonus near curvimaculatus.

The 33,000 Dalton venom protein of Chelonus near curvimaculatus was characterized for structural properties of charge, quaternary associations, and relationship to polydnavirus encoded proteins. Homogenous isoforms of the protein were isolated from the venom by sequential steps of 1) microdissection, 2) separation based on charge (Mono-Q column HPLC or narrow-range electrofocusing), and 3) centrifugal filtration based on molecular weight using Centricon microconcentrators. The purified protein dimerized under native conditions, and this quaternary association became denaturation resistant under certain conditions. Chemical modification of lysine epsilon amino groups did not disrupt such dimerization. The cDNA for the protein did not possess high similarity to any sequence encoded in the polydnavirus, as indicated by results of Southern blotting, but does possess similarity in its repeats to the repeats of the immunologically protective surface glycoprotein of Leishmania amazonensis.

Amino Acid Sequence↗
PubMed1996

Transformation of gypsy moth (Lymantria dispar) cell lines by infection with Glyptapanteles indiensis polydnavirus.

Glyptapanteles indiensis, a species of braconid parasitic wasp, infects its host Lymantria dispar (gypsy moth) with a polydnavirus (GiPDV) to suppress the host immune system during parasitization. Here it is shown that GiPDV can infect L. dispar cell lines and that a portion of the GiPDV genome is stably maintained in infected cells. Results of Southern hybridization analyses suggested that this portion of the GiPDV genome is integrated into the L. dispar cellular genome. This is the first report of an insect viral DNA molecule that can apparently integrate into lepidopteran insect cells.

Animals↗
PubMed2000

Functional significance of parasitism-induced suppression of juvenile hormone esterase activity in developmentally delayed Choristoneura fumiferana larvae.

The parasitic wasp Tranosema rostrale transmits a polydnavirus (PDV) to its host, Choristoneura fumiferana, during oviposition. Last-instar C. fumiferana larvae parasitized by T. rostrale early in the stadium fail to undergo metamorphosis, and injection of the wasp's calyx fluid (CxF; contains PDV) into healthy caterpillars induces a dose-dependent delay in initiation of metamorphosis (D. Doucet and M. Cusson, 1996, Entomol. Exp. Appl. 81, 21-30). In the present work, parasitization and injection of CxF (0.5 female equivalent) on the first day of the last stadium both prevented the rise in hemolymph 20-hydroxyecdysone (20HE) titer observed between day 4 and day 7 in control and saline-injected larvae. Similarly, juvenile hormone esterase (JHE) activity was depressed following parasitization or CxF injection, whereas control larvae displayed a peak on day 4. However, neither parasitism nor injection of CxF on day 1 prevented the JH-producing glands from turning off during the first half of the last stadium. Likewise, low but clearly detectable JH titers were observed in the first hours following the molt but very low titers, at or near the detection limit of our radioimmunoassay, were seen in both control and parasitized larvae on day 4. Prothoracic glands showed no apparent sign of degeneration 4 days after injection of CxF but had significantly smaller cells than saline-injected larvae 7 days postinjection. It is not clear whether this was a direct effect of T. rostrale PDV. Thus, disruption of spruce budworm metamorphosis by T. rostrale CxF involves depression of 20HE titers but is not associated with a measurable increase in the level of JH, as shown for some other host-parasitoid systems. In view of the latter observation, we put forward three hypotheses regarding the functional significance of the observed suppression of JHE activity in developmentally arrested C. fumiferana larvae.

Animals↗
PubMed1998

A polydnavirus from the spruce budworm parasitoid, Tranosema rostrale (Ichneumonidae).

The calyx epithelium of the campoplegine wasp, Tranosema rostrale, contains typical ichneumonid polydnaviruses (PVs) that display an apparently uncommon association with the egg chorion. The latter structure features fine hair-like projections, longest around the egg's apices. In the lumen of the ovary, T. rostrale virus becomes lodged between these projections and forms a particulate coat around the egg. In the host, Choristoneura fumiferana, projections and associated virions are observed in close contact with basement membranes of fat body and muscle tissues, to which the eggs rapidly become attached following introduction into the host hemocoel. We discuss the implications of this unusual virus-chorion association in terms of immune protection, delivery of virus to specific host tissues, and the evolution of PVs.

Animals↗
PubMed2001

Effects of Glyptapanteles liparidis (Hym.: Braconidae) parasitism, polydnavirus, and venom on development of microsporidia-infected and uninfected Lymantria dispar (Lep.: Lymantriidae) larvae.

Effects of parasitism, polydnavirus, and venom of the endoparasitoid Glyptapanteles liparidis on Lymantria dispar larvae infected with the microsporidium Vairimorpha sp. and uninfected hosts were studied. We tested the impact on growth and development of hosts, as well as on microsporidian infection. Both parasitism and polydnavirus/venom treatment alone caused a slight increase in growth rate and relative growth rate in uninfected fourth instar hosts. This effect was more pronounced with the addition of Vairimorpha infection. With no parasitism, however, infection reduced host growth markedly. Microsporidiosis delayed larval molts of L. dispar, and additional polydnavirus/venom treatment or parasitization induced significantly earlier molting. Polydnavirus/venom treatment of uninfected L. dispar resulted in prolonged larval development due to supernumerary molts and in higher pupal mortality. Infected larvae treated with polydnavirus/venom died earlier than infected larvae that were not treated and produced more Vairimorpha spores per unit fresh mass of the host.

Animals↗
PubMed1994

An abundantly expressed hemolymph glycoprotein isolated from newly parasitized Manduca sexta larvae is a polydnavirus gene product.

Cotesia congregata polydnavirus (CcPDV) is essential for successful parasitism of Manduca sexta larvae by the braconid wasp C. congregata. CcPDV virions are present in large numbers in the oviducts of C. congregata and injected with eggs into the hemocoel of M. sexta larvae during parasitization. Injection of sucrose density purified virions into nonparasitized larvae causes several of the parasitism-induced alterations in the physiology of host larvae that occur as a result of natural parasitism, including the synthesis of novel hemolymph proteins and abrogation of the host's immune response against the developing parasites. One of these proteins, early-expressed protein 1 (EP1), is a 190-kDa molecule which constitutes up to 5% of the total hemolymph protein by 24 hr following oviposition by the wasp. Using N-terminal sequence data for EP1 to construct primers for use in the polymerase chain reaction, we amplified and cloned a cDNA corresponding to the gene encoding EP1. This cDNA hybridized to DNA of the CcPDV genome, but not to DNA isolated from M. sexta larvae, suggesting that EP1 is a CcPDV gene product. A cDNA clone was isolated from an expression library generated from RNA extracted from newly parasitized M. sexta larvae. Sequence analysis of the cDNA clone revealed the presence of an open reading frame of 819 bp encoding a protein of 30.7 kDa. In vitro transcription/translation of the cDNA clone produced a protein of approximately 31 kDa, which was immunoprecipitated by EP1-specific polyclonal antiserum generated against purified deglycosylated EP1. EP1-like sequences also were amplified from male wasp genomic DNA, suggestive of integration of EP1-like sequences in the genome. This report constitutes the first evidence that a specific protein isolated from a parasitized host insect is a wasp polydnavirus gene product.

Amino Acid Sequence↗
PubMed1999

Related RNAs in lepidopteran cells after in vitro infection with Hyposoter didymator virus define a new polydnavirus gene family.

In the present study, we describe the isolation and the characterization of three different Hyposoter didymator virus (HdV) lepidopteran host-expressed genes, the products of which might interfere with the host physiology during parasitism. In this report, we study the expression of HdV genes in Sf9 cells infected with HdV since results indicate that the Sf9 model mimics to some extent the in vivo model and may be utilized to study expression of HdV genes in lepidopteran host cells. This system allowed us to isolate three HdV-specific cDNAs, termed M24, M27, and M40. cDNA nucleotide sequence analysis demonstrated significant regions of homology. The three cDNAs displayed repeated sequences arranged in tandem array that might have evolved through domain duplication. Similar to other previously described polydnavirus host-expressed genes, two intron positions have been found in the M24 leader region. The cDNAs corresponded to RNAs of 1.5, 1.6, and 2.3 kb that are also detected in parasitized Spodoptera littoralis larvae. They are encoded by different genes likely located on different HdV DNA molecules. Corresponding RNAs are detected early postinfection and remain detectable for at least 10 days postinfection. They encode secreted glycine- and proline-rich proteins. An antiserum raised against a baculovirus recombinant M24-encoded protein detected similar proteins in the culture medium of infected lepidopteran cells and in parasitized host hemolymph. We propose that the three cloned genes belong to an HdV gene family specifically expressed in parasitized lepidopteran hosts.

Amino Acid Sequence↗
PubMed2000

A gene encoding a polydnavirus structural polypeptide is not encapsidated.

Polydnaviruses are symbiotic viruses associated with some parasitic Hymenoptera that are vertically transmitted as proviruses within wasp genomes. To study this symbiotic association a gene encoding an abundant Campoletis sonorensis polydnavirus virion protein was characterized. This gene is not encapsidated but resides in the wasp genome where it is expressed only during virus replication. Immunolocalization studies detected the encoded 44-kDa protein only in oviduct tissue with ultrastructural studies detecting epitopes between or on virion envelopes. Expression and localization of the 44-kDa protein are consistent with its being a viral structural protein but localization of the gene only within the wasp genome is atypical, raising the possibility that this protein is adventitiously packaged during virion assembly. To address this possibility, quantitative dot blot and genomic Southern blot hybridizations were performed to determine whether the copy number of the p44 gene increased disproportionately during replication, as would be expected for a gene encoding a virion protein. The copy number of the p44 gene increases in tissues supporting virus replication but is unchanged in other tissues, suggesting that this gene is amplified in replicative cells. The data indicate that genes encoding polydnavirus virion proteins may be distributed between wasp and encapsidated viral genomes.

Amino Acid Sequence↗
PubMed2000

Co-replication of a reovirus and a polydnavirus in the ichneumonid parasitoid Hyposoter exiguae.

A recently established colony of the ichneumonid parasitoid, Hyposoter exiguae, was found to carry both a reovirus (HeRV) and a polydnavirus (HePDV). Morphogenesis of these viruses was observed in all cells comprising the ovarian calyx epithelium, apparently without detrimental effect to the parasitoid. While polydnavirus replication in H. exiguae was restricted to the calyx region, HeRV was detected in ovarioles, oviducts, midguts, malpighian tubules, and accessory glands associated with the male reproductive system. In addition, HeRV was able to infect the fat body of parasitized host larvae and to establish a persistent infection in vitro. Electron microscopy revealed that both viruses were released into the calyx fluid compartment exclusively by budding, a phenomenon rarely observed among the Reoviridae; HeRV envelopes thus obtained, however, appeared to be subsequently shed within the oviducts. HeRV particles were concentrated to near homogeneity by differential centrifugation; mature virions consisted of seven to eight structural polypeptides and 10 dsRNA genome segments. Prominent spikes were observed at the vertices of icosahedral core particles. Most, but not all, individuals comprising the H. exiguae colony appeared to be infected with HeRV, suggesting a commensal relationship between wasp and virus; however, while this association is of obvious benefit to the virus, it seems unlikely that any advantage accrues to the parasitoid which carries it.

Animals↗
PubMed2002

Evidence for a conserved polydnavirus gene family: ichnovirus homologs of the CsIV repeat element genes.

In Campoletis sonorensis Ichnovirus (CsIV), the repeat element genes constitute a gene family of 28 members. In the present work, we document the presence of members of this gene family in two additional ichnoviruses, Hyposoter didymator Ichnovirus (HdIV) and Tranosema rostrale Ichnovirus (TrIV). Two repeat element genes, representing at least one functional gene, were identified in TrIV, whereas HdIV was found to contain at least three such genes. In both HdIV and TrIV, the known repeat element genes are encoded on single genome segments, with hybridization studies suggesting the presence of other, related but as yet uncharacterized genes. The HdIV and TrIV repeat element genes are all transcribed in infected caterpillars, although differences exist among genes in levels and in tissue specificity of expression. A heuristic tree was generated indicating that the repeat element genes are more similar within a species of wasp than between species, with TrIV genes being more closely related to the CsIV than to the HdIV genes. These results suggest that the most significant duplication, divergence, and expansion of the repeat element genes occurred after speciation. The finding that repeat element genes form an interspecific family within the genus Ichnovirus supports the view that the proteins they encode play an important role in ichnovirus biology.

Amino Acid Sequence↗
PubMed2003

Diversifying selection in a parasitoid's symbiotic virus among genes involved in inhibiting host immunity.

During parasitization of their hosts some insect parasitoids deliver resident viruses which encode genes that must be expressed in the host for successful parasitization. Among these viruses the Campoletis sonorensis Ichnovirus has been well studied and encodes a cys-motif gene family implicated in disruption of host immunity and other physiological systems. Members of this gene family encode one or more intercystine-knot structural motifs in which the non-cysteine residues of the motif are variable. We analyzed patterns of synonymous and non-synonymous substitution within the cys-motif to investigate the evolution of this gene family and the likelihood of virus-host gene coevolution. Maximum likelihood techniques suggest positive selection acts on 8 of 51 codons in the aligned cysteine-rich region. Although the detected positive selection was not strong, it likely contributes to the diversification of this gene family. Comparison of selection pressure relative to tertiary structure of the VHv1.1 cys-motif protein suggests that the hypervariable sites are exposed. Furthermore, invariant residues in the motif exhibit a region-specific pattern of codon bias, suggesting there are unusual mechanisms of effecting selection pressure at work in this system, though the mechanism has yet to be studied. The positive selection and duplication of both the gene family and the cys-motif implies either selection is driving the molecular radiation of immune suppressive genes toward novel hosts, or molecular coevolution with host targets.

Animals↗
PubMed2001

Promoter studies of a polydnavirus gene from Cotesia rubecula (Hym: Braconidae).

The Cotesia rubecula polydnavirus gene, CrV1, is expressed in a highly transient fashion. Within four hours after egg deposition and virus infection, tissues of the host caterpillar, Pieris rapae, express high levels of the transcript. Twelve hours after infection no transcripts are visible. We have previously shown that the CrV1 secreted protein is mainly produced in host haemocytes. In haemocytes, immune functions such as phagocytosis and cell spreading are abolished by destabilization of the cell cytoskeleton. To test whether the observed down-regulation of CrV1 transcripts is mediated by transcriptional control or by other factors, such as the disruption of cytoskeleton in CrV1-inactivated cells, we cloned the promoter and the 3' untranslated region of the CrV1 gene to study CrV1 expression. The promoter region of the CrV1 gene was cloned into baculovirus expression systems along with the CAT reporter gene. Molecular analyses showed that the CAT gene under the control of CrV1 promoter is expressed as early as 2 h post infection and continues until late phase of infection suggesting that down-regulation of CrV1 expression in host haemocytes is perhaps mediated by post-transcriptional mechanisms.

Animals↗
PubMed1999

Transformation of lepidopteran and coleopteran insect cell lines by Glyptapanteles indiensis polydnavirus DNA.

Recently investigators showed that polydnavirus DNA from the parasitic wasp Glyptapanteles indiensis could transform gypsy moth L. dispar cell lines in vitro (McKelvey et al., 1996). Here we show GiPDV DNA is capable of transforming in vitro to varying degrees lepidopteran (IPLB-TN-R2, IPLB-SF-21, IAL-PID2, IPLB-HvT1) and coleopteran (IPLB-DU182E) insect cell lines derived from various somatic tissue types. An insect cell line derived from dipteran Aedes albopictus (C7/10) could not be transformed with G. indiensis polydnavirus.

Aedes↗
PubMedDate not supplied

Interaction of a wasp ovarian protein and polydnavirus in host immune suppression.

During parasitization of Heliothis virescens, Campoletis sonorensis deposits an egg along with venom, polydnavirus particles (CsPDV), and ovarian proteins (OPs). Oviposited eggs are not encapsulated, while washed eggs are encapsulated rapidly by H. virescens. Early protection from encapsulation is afforded by a group of 29-36 kD OP glycoforms. These glycoforms are endocytosed by host hemocytes within 30 min post-parasitization (pp) and disrupt hemocyte spreading behavior and egg encapsulation through at least 24 h p.i. Purified CsPDV does not protect eggs from encapsulation early, but disrupts hemocyte spreading and egg encapsulation from 24 h through at least 5 days p.i. Functional activity of CsPDV appears to be correlated with time-dependent accumulation of virus-specific proteins in parasitized insects. We propose that the fast-acting 29-36 kD OP protects Campoletis eggs from encapsulation until accumulation of CsPDV proteins which sustain immunosuppression.

Animals↗