1
|
Seehausen ML, Naumann PH, Béliveau C, Martel V, Cusson M. Impact of rearing temperature on encapsulation and the accumulation of transcripts putatively involved in capsule formation in a parasitized lepidopteran host. JOURNAL OF INSECT PHYSIOLOGY 2018; 107:244-249. [PMID: 29704478 DOI: 10.1016/j.jinsphys.2018.04.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 04/24/2018] [Accepted: 04/24/2018] [Indexed: 06/08/2023]
Abstract
Encapsulation and melanisation are innate immune reactions of insects against foreign intruders such as parasitoids. In an earlier study, we observed that immature life stages of the endoparasitoid Tranosema rostrale (Hymenoptera: Ichneumonidae) parasitizing Choristoneura fumiferana (Lepidoptera: Tortricidae) larvae experienced higher mortality due to encapsulation and melanisation when reared at high (30 °C) than at lower (10 °C, 20 °C) temperatures. Downregulation of T. rostrale polydnavirus genes in parasitized hosts and upregulation of two genes involved in the spruce budworm's melanisation process were identified as likely contributors to parasitoid mortality at high temperature. However, levels of transcripts of genes involved in the spruce budworm's cellular encapsulation process were not measured inasmuch as candidate genes, in the spruce budworm, had not yet been identified. In addition, our assessment of temperature-dependent encapsulation and melanisation of foreign objects in spruce budworm larvae was only partial. To fill these knowledge gaps, we injected Sephadex™ beads into unparasitized spruce budworm larvae and assessed their encapsulation/melanisation after the insects had been held at three different temperatures (10, 20, and 30 °C), and we identified spruce budworm genes putatively involved in the encapsulation process and quantified their transcripts at the same three temperatures, using a qPCR approach. As expected, both encapsulation and melanisation of Sephadex™ beads increased as a function of temperature. At the molecular level, three of the five genes examined (Integrin β1, Hopscotch, Stat92E) clearly displayed temperature-dependent upregulation. The results of this study further support the hypothesis that a temperature-dependent increase in the encapsulation response of C. fumiferana against T. rostrale is due to the combined effects of reduced expression of polydnavirus genes and enhanced expression of host immune genes.
Collapse
Affiliation(s)
- M Lukas Seehausen
- University of Toronto, Faculty of Forestry, 33 Willcocks Street, Toronto, Ontario M5S 3B3, Canada.
| | - Paul-Henri Naumann
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Quebec City G1V 4C7, Canada
| | - Catherine Béliveau
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Quebec City G1V 4C7, Canada
| | - Véronique Martel
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Quebec City G1V 4C7, Canada
| | - Michel Cusson
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Quebec City G1V 4C7, Canada
| |
Collapse
|
2
|
Seehausen ML, Cusson M, Régnière J, Bory M, Stewart D, Djoumad A, Smith SM, Martel V. High temperature induces downregulation of polydnavirus gene transcription in lepidopteran host and enhances accumulation of host immunity gene transcripts. JOURNAL OF INSECT PHYSIOLOGY 2017; 98:126-133. [PMID: 28041943 DOI: 10.1016/j.jinsphys.2016.12.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 12/23/2016] [Indexed: 06/06/2023]
Abstract
Endoparasitoids face the challenge of overcoming the immune reaction of their hosts, which typically consists of encapsulation and melanisation of parasitoid eggs or larvae. Some endoparasitic wasps such as the solitary Tranosema rostrale (Hymenoptera: Ichneumonidae) that lay their eggs in larvae of the spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae), have evolved a symbiotic relationship with a polydnavirus (PDV), which in turn helps them suppress the host's immune response. We observed an increase in mortality of immature T. rostrale with increasing temperature, and we tested two hypotheses about the mechanisms involved: high temperatures (1) hamper the expression of T. rostrale PDV genes and (2) enhance the expression of spruce budworm immunity-related genes. Dissections of parasitized spruce budworm larvae reared at 30°C revealed that most parasitoid eggs or larvae had died as a result of encapsulation and melanisation by the host. A qPCR analysis of T. rostrale PDV (TrIV) gene expression showed that the transcription of several TrIV genes in host larvae was downregulated at high temperature. On the other hand, encapsulation, but not melanisation, of foreign bodies in spruce budworm larvae was enhanced at high temperatures, as shown by the injection of Sephadex™ beads into larvae. However, at the molecular level, the transcription of genes related to spruce budworm's melanisation process (prophenoloxidase 1 and 2) was upregulated. Our results support the hypothesis that a temperature-dependent increase of encapsulation response is due to the combined effects of reduced expression of TrIV genes and enhanced expression of host immune genes.
Collapse
Affiliation(s)
- M Lukas Seehausen
- University of Toronto, Faculty of Forestry, 33 Willcocks Street, Toronto, Ontario M5S 3B3, Canada.
| | - Michel Cusson
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Québec G1V 4C7, Canada
| | - Jacques Régnière
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Québec G1V 4C7, Canada
| | - Maxence Bory
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Québec G1V 4C7, Canada
| | - Don Stewart
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Québec G1V 4C7, Canada
| | - Abdelmadjid Djoumad
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Québec G1V 4C7, Canada
| | - Sandy M Smith
- University of Toronto, Faculty of Forestry, 33 Willcocks Street, Toronto, Ontario M5S 3B3, Canada
| | - Véronique Martel
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., Québec G1V 4C7, Canada
| |
Collapse
|
3
|
Dorémus T, Darboux I, Cusson M, Ravallec M, Jouan V, Frayssinet M, Stoltz DB, Webb BA, Volkoff AN. Specificities of ichnoviruses associated with campoplegine wasps: genome, genes and role in host-parasitoid interaction. CURRENT OPINION IN INSECT SCIENCE 2014; 6:44-51. [PMID: 32846675 DOI: 10.1016/j.cois.2014.09.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 09/23/2014] [Accepted: 09/24/2014] [Indexed: 06/11/2023]
Abstract
Ichnoviruses (IVs), unique symbiotic viruses carried by ichneumonid campoplegine wasps, derive from integration of a paleo-ichnovirus into an ancestral wasp genome. The modern 'genome' is composed of both regions that are amplified, circularized and encapsidated into viral particles and non-encapsidated viral genomic regions involved in particle morphogenesis. Packaged genomes include multiple circular dsDNAs encoding many genes mostly organized in gene families. Virus particles are assembled in specialized ovarian cells from which they exit into the oviduct lumen; mature virions are injected during oviposition into the insect host. Expression of viral proteins in infected cells correlates with physiological alterations of the host enabling success of parasitism.
Collapse
Affiliation(s)
- Tristan Dorémus
- "Diversity, Genomes & Interactions Microorganisms Insects" Laboratory, INRA (UMR 1333), Université de Montpellier 2, Place Eugène Bataillon, CC101, 34095 Montpellier Cedex, France
| | - Isabelle Darboux
- "Diversity, Genomes & Interactions Microorganisms Insects" Laboratory, INRA (UMR 1333), Université de Montpellier 2, Place Eugène Bataillon, CC101, 34095 Montpellier Cedex, France
| | - Michel Cusson
- Laurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, 1055 du P.E.P.S., P.O. Box 10380, Stn. Ste. Foy, Quebec G1V 4C7, Canada
| | - Marc Ravallec
- "Diversity, Genomes & Interactions Microorganisms Insects" Laboratory, INRA (UMR 1333), Université de Montpellier 2, Place Eugène Bataillon, CC101, 34095 Montpellier Cedex, France
| | - Véronique Jouan
- "Diversity, Genomes & Interactions Microorganisms Insects" Laboratory, INRA (UMR 1333), Université de Montpellier 2, Place Eugène Bataillon, CC101, 34095 Montpellier Cedex, France
| | - Marie Frayssinet
- "Diversity, Genomes & Interactions Microorganisms Insects" Laboratory, INRA (UMR 1333), Université de Montpellier 2, Place Eugène Bataillon, CC101, 34095 Montpellier Cedex, France
| | - Don B Stoltz
- Department of Microbiology and Immunology, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, P.O. Box 15000, Halifax, Nova Scotia B3H 4R2, Canada
| | - Bruce A Webb
- Department of Entomology, S-225 Agricultural Science Center N, University of Kentucky, Lexington, KY 40546-0091, USA
| | - Anne-Nathalie Volkoff
- "Diversity, Genomes & Interactions Microorganisms Insects" Laboratory, INRA (UMR 1333), Université de Montpellier 2, Place Eugène Bataillon, CC101, 34095 Montpellier Cedex, France.
| |
Collapse
|
4
|
Djoumad A, Dallaire F, Lucarotti CJ, Cusson M. Characterization of the polydnaviral ‘T. rostrale virus’ (TrV) gene family: TrV1 expression inhibits in vitro cell proliferation. J Gen Virol 2013; 94:1134-1144. [DOI: 10.1099/vir.0.049817-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Tranosema rostrale ichnovirus (TrIV) is a polydnavirus (PDV) transmitted by the endoparasitic wasp T. rostrale to its host Choristoneura fumiferana during oviposition. PDV genes are expressed in infected caterpillars, causing physiological disturbances that promote the survival of the developing endoparasite. The previously sequenced genome of TrIV contains ~86 genes organized in multigene families and distributed on multiple segments of circular dsDNA. Among these, the ‘T. rostrale virus’ (TrV) family comprises seven genes that are absent in other PDV genomes examined to date and whose function(s) remain(s) unknown. Here, we initiated a functional analysis of the TrV family using qPCR, transfection and RNAi approaches. TrV family genes were weakly expressed in wasp ovaries, but some displayed high transcript abundance in parasitized caterpillars. Whilst TrV1 was the most highly transcribed TrV gene in infected caterpillars, transcript levels for TrV5 and TrV6 were nearly undetectable, indicating that they may be pseudogenes. Temporal and tissue-specific patterns of transcript abundance were similar for all expressed TrV family genes, indicative of an apparent lack of difference in function or tissue specificity. Infection of Cf-203 and Sf-21 insect cells with TrIV led to a dose-dependent inhibition of cell proliferation with no sign of apoptosis. Whilst similar inhibition was observed following transfection of cells with a cloned genome segment carrying the TrV1 gene, RNA interference targeting TrV1 largely restored cell growth in TrIV-infected cells, indicating that TrV1 expression was responsible for the observed inhibition. We suggest that TrV genes may contribute to host developmental disruption by interfering with host-cell proliferation during parasitism.
Collapse
Affiliation(s)
- Abdelmadjid Djoumad
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn. Sainte‐Foy, Québec, Quebec G1V 4C7, Canada
| | - Fréderic Dallaire
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn. Sainte‐Foy, Québec, Quebec G1V 4C7, Canada
| | - Christopher J. Lucarotti
- Natural Resources Canada, Canadian Forest Service, Atlantic Forestry Centre, 1350 Regent Street, Fredericton, New Brunswick E3C 2G6, Canada
| | - Michel Cusson
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn. Sainte‐Foy, Québec, Quebec G1V 4C7, Canada
| |
Collapse
|
5
|
Dorémus T, Jouan V, Urbach S, Cousserans F, Wincker P, Ravallec M, Wajnberg E, Volkoff AN. Hyposoter didymator uses a combination of passive and active strategies to escape from the Spodoptera frugiperda cellular immune response. JOURNAL OF INSECT PHYSIOLOGY 2013; 59:500-508. [PMID: 23458339 DOI: 10.1016/j.jinsphys.2013.02.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 02/19/2013] [Accepted: 02/20/2013] [Indexed: 06/01/2023]
Abstract
An endoparasitic life style is widespread among Hymenoptera, and various different strategies allowing parasitoids to escape from the host encapsulation response have been reported. Species carrying polydnaviruses (PDVs), such as the ichneumonid Hyposoter didymator, generally rely on the viral symbionts to evade host immune responses. In this work, we show that H. didymator eggs can evade encapsulation by the host in the absence of calyx fluid (containing the viral particles), whereas protection of the larvae requires the presence of calyx fluid. This evasion by the eggs depends on proteins associated with the exochorion. This type of local passive strategy has been described for a few species carrying PDVs. Immune evasion by braconid eggs appears to be related to PDVs or proteins synthesized in the oviducts being associated with the egg. We report that in H. didymator, by contrast, proteins already present in the ovarian follicles are responsible for the eggs avoiding encapsulation. Mass spectrometry analysis of the egg surface proteins revealed the presence of host immune-related proteins, including one with similarities with apolipophorin-III, and also the presence of three viral proteins encoded by IVSPERs (Ichnovirus Structural Protein Encoding Regions).
Collapse
Affiliation(s)
- Tristan Dorémus
- INRA (UMR 1333), Université de Montpellier 2, Insect-Microorganisms Diversity, Genomes and Interactions, Place Eugène Bataillon, CC101, 34095 Montpellier Cedex, France
| | | | | | | | | | | | | | | |
Collapse
|
6
|
Huang F, Shi M, Chen YF, Cao TT, Chen XX. Oogenesis of Diadegma semiclausum (Hymenoptera: Ichneumonidae) and its associated polydnavirus. Microsc Res Tech 2008; 71:676-83. [PMID: 18454475 DOI: 10.1002/jemt.20594] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We present a detailed ultrastructural analysis of ovary and calyx cell differentiation of Diadegma semiclausum. Numerous gametangia in various developmental stages were examined with electron microscopy to characterize the ultrastructure features of oogenesis, the most important of which is the development of nurse cells. In the germarium, the undifferentiated germ cells diversify, and one of the central cells of the cluster differentiates into an oocyte while the remaining become nurse cells. Germ cells continue developing in the vitellarium until mature and then enter into the calyx region. The calyx epithelium contains typical ichneumonid polydnaviruses with the following characteristics: (1) the virus particles assemble in the nuclei of calyx cells where they acquire an initial (inner) membrane, then migrate through the cytoplasm and budd out into the lumen of the ovary, at which time they acquire a second envelope (outer membrane); (2) the particle has a genome comprising several DNA segments. However, this new polydnavirus (Diadegma semiclausum polydnavirus) in the genus ichnovirus was not attached to the surface of the egg chorion.
Collapse
Affiliation(s)
- Fang Huang
- Institute of Insect Sciences, Zhejiang University, Hangzhou 310029, China
| | | | | | | | | |
Collapse
|
7
|
Stoltz D, Lapointe R, Makkay A, Cusson M. Exposure of ichnovirus particles to digitonin leads to enhanced infectivity and induces fusion from without in an in vitro model system. J Gen Virol 2007; 88:2977-2984. [PMID: 17947519 DOI: 10.1099/vir.0.83118-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Unlike most viruses, the mature ichnovirus particle possesses two unit membrane envelopes. Following loss of the outer membrane in vivo, nucleocapsids are believed to gain entry into the cytosol via a membrane fusion event involving the inner membrane and the plasma membrane of susceptible host cells; accordingly, experimentally induced damage to the outer membrane might be expected to increase infectivity. Here, in an attempt to develop an in vitro model system for studying ichnovirus infection, we show that digitonin-induced disruption of the virion outer membrane not only increases infectivity, but also uncovers an activity not previously associated with any polydnavirus: fusion from without.
Collapse
Affiliation(s)
- Don Stoltz
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 4H7, Canada
| | - Renée Lapointe
- Laurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, Quebec City, QC G1V 4C7, Canada
| | - Andrea Makkay
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 4H7, Canada
| | - Michel Cusson
- Laurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, Quebec City, QC G1V 4C7, Canada
| |
Collapse
|
8
|
Tanaka K, Lapointe R, Barney WE, Makkay AM, Stoltz D, Cusson M, Webb BA. Shared and species-specific features among ichnovirus genomes. Virology 2007; 363:26-35. [PMID: 17306851 DOI: 10.1016/j.virol.2006.11.034] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Revised: 09/13/2006] [Accepted: 11/13/2006] [Indexed: 10/23/2022]
Abstract
During egg-laying, some endoparasitic wasps transmit a polydnavirus to their caterpillar host, causing physiological disturbances that benefit the wasp larva. Members of the two recognized polydnavirus taxa, ichnovirus (IV) and bracovirus (BV), have large, segmented, dsDNA genomes containing virulence genes expanded into families. A recent comparison of IV and BV genomes revealed taxon-specific features, but the IV database consisted primarily of the genome sequence of a single species, the Campoletis sonorensis IV (CsIV). Here we describe analyses of two additional IV genomes, the Hyposoter fugitivus IV (HfIV) and the Tranosema rostrale IV (TrIV), which we compare to the sequence previously reported for CsIV. The three IV genomes share several features including a low coding density, a strong A+T bias, similar estimated aggregate genome sizes ( approximately 250 kb) and the presence of nested genome segments. In addition, all three IV genomes contain members of six conserved gene families: repeat element, cysteine motif, viral innexin, viral ankyrin, N-family, and a newly defined putative family, the polar-residue-rich proteins. The three genomes, however, differ in their degree of segmentation, in within-family gene frequency and in the presence, in TrIV, of a unique gene family (TrV). These interspecific variations may reflect differences in parasite/host biology, including virus-induced pathologies in the latter.
Collapse
Affiliation(s)
- Kohjiro Tanaka
- Department of Entomology, University of Kentucky, Lexington, KY 40503, USA.
| | | | | | | | | | | | | |
Collapse
|
9
|
Doucet D, Levasseur A, Béliveau C, Lapointe R, Stoltz D, Cusson M. In vitro integration of an ichnovirus genome segment into the genomic DNA of lepidopteran cells. J Gen Virol 2007; 88:105-113. [PMID: 17170442 DOI: 10.1099/vir.0.82314-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polydnaviruses (PDVs) are dsDNA viruses transmitted by ichneumonid and braconid endoparasitoids to their lepidopteran hosts during oviposition. Wasp carriers are asymptomatic and transmit the virus to their progeny through the germ line; replication is confined to the calyx region of the wasp ovary, where the virus accumulates in the fluid bathing the eggs. In the lepidopteran host, however, no virus replication takes place, but PDV gene expression is essential for successful parasitism. Sustained gene expression in the absence of virus replication thus requires that the circular PDV genome segments persist for days within host cells. Available evidence suggests that most genome segments persist as episomes, but recent studies have indicated that some genome segments may undergo integration within lepidopteran genomic DNA, at least in vitro. In the present study, an integrated form of a Tranosema rostrale ichnovirus (TrIV) genome segment was cloned from genomic DNA extracted from infected Choristoneura fumiferana CF-124T cells and junction regions on either side of the viral DNA sequence were sequenced. This is the first proven example of integration of an ichnovirus genome segment in infected lepidopteran cells. Interestingly, circular forms of this genome segment do not appear to persist in these cells; none the less, a gene (TrFrep1) carried by this genome segment displays long-term transcription in infected cultured cells.
Collapse
Affiliation(s)
- Daniel Doucet
- Department of Microbiology and Immunology, Sir Charles Tupper Medical Building, Dalhousie University, Halifax, NS B3H 4H7, Canada
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn Ste-Foy, Quebec City, QC G1V 4C7, Canada
| | - Anic Levasseur
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn Ste-Foy, Quebec City, QC G1V 4C7, Canada
| | - Catherine Béliveau
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn Ste-Foy, Quebec City, QC G1V 4C7, Canada
| | - Renée Lapointe
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn Ste-Foy, Quebec City, QC G1V 4C7, Canada
| | - Don Stoltz
- Department of Microbiology and Immunology, Sir Charles Tupper Medical Building, Dalhousie University, Halifax, NS B3H 4H7, Canada
| | - Michel Cusson
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du PEPS, PO Box 10380, Stn Ste-Foy, Quebec City, QC G1V 4C7, Canada
| |
Collapse
|
10
|
Kroemer JA, Webb BA. Polydnavirus genes and genomes: emerging gene families and new insights into polydnavirus replication. ANNUAL REVIEW OF ENTOMOLOGY 2004; 49:431-456. [PMID: 14651471 DOI: 10.1146/annurev.ento.49.072103.120132] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Polydnavirus genome sequencing is providing new insights into viral genome organization and viral gene function. Sequence analyses demonstrate that the genomes of these viral mutualists are largely noncoding but maintain genes and gene families that are unrelated to other viral genes. Interestingly, these organizational patterns in polydnavirus genomes are evident in both the bracovirus and ichnovirus genera, even though these two genera are evolutionarily unrelated. The identity and function of some polydnavirus gene families are considered with some functions experimentally supported and others implied by homology relationships with known insect genes. The evidence relative to polydnavirus origins and evolution is considered but remains an area of speculation. However, sequencing of these viral genomes has been informative and provides opportunities for productive investigation of these unusual mutualistic insect viruses.
Collapse
Affiliation(s)
- Jeremy A Kroemer
- Department of Entomology, University of Kentucky, S-225 Agricultural Sciences Center North, Lexington, Kentucky 40546, USA.
| | | |
Collapse
|
11
|
Wyler T, Lanzrein B. Ovary development and polydnavirus morphogenesis in the parasitic wasp Chelonus inanitus. II. Ultrastructural analysis of calyx cell development, virion formation and release. J Gen Virol 2003; 84:1151-1163. [PMID: 12692280 DOI: 10.1099/vir.0.18830-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polydnaviruses are unique symbiotic viruses that are formed only in calyx cells in the ovary of parasitic wasps in the families Braconidae and Ichneumonidae; accordingly, two genera, Bracovirus and Ichnovirus are recognized. We have presented a detailed ultrastructural analysis of ovary and calyx cell differentiation and virion morphogenesis, together with the first data on virion release in a bracovirus. Differentiation of the ovary into germarium/vitellarium and the calyx region begins immediately after pupation. In the periphery and central part of the calyx, some cells and their nuclei begin to enlarge and the DNA content increases. The calyx cell nuclei then further increase and become highly lobulated, nuclear pores become very abundant and the cytoplasm is rich in ribosomes. This suggests synthesis and import of viral envelope proteins as viral envelopes appear in the nuclei shortly later. The appearance of viral envelopes is accompanied by a swelling of the nucleus and a change in electron density. Thereafter, the calyx cells reach the final stage with a highly swollen nucleus containing virogenic stroma and mature virions with nucleocapsids. Up to this stage, the DNA content of nuclei increases 120-fold and the volume 45-fold. The mature calyx cells are positioned in the vicinity of the oviduct lumen; for release of virions first the nuclear and then the plasma membrane disintegrate. On the border of the oviduct lumen, cells of an epithelial layer become phagocytic and remove debris, leading to a calyx fluid that contains only densely packed virions.
Collapse
Affiliation(s)
- Toni Wyler
- Institute of Cell Biology, University of Berne, Baltzerstrasse 4, CH-3012 Bern, Switzerland
| | - Beatrice Lanzrein
- Institute of Cell Biology, University of Berne, Baltzerstrasse 4, CH-3012 Bern, Switzerland
| |
Collapse
|
12
|
Galibert L, Rocher J, Ravallec M, Duonor-Cérutti M, Webb BA, Volkoff AN. Two Hyposoter didmator ichnovirus genes expressed in the lepidopteran host encode secreted or membrane-associated serine and threonine rich proteins in segments that may be nested. JOURNAL OF INSECT PHYSIOLOGY 2003; 49:441-451. [PMID: 12770623 DOI: 10.1016/s0022-1910(03)00061-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present in this work two novel Hyposoter didymator ichnovirus genes expressed in parasitized Spodoptera larvae. These genes, named HdCorfS6 and HdGorfP30, are unrelated and present in two different genome segments, possibly nested, SH-C and SH-G respectively. HdCorfS6 encodes a predicted transmembrane protein, putatively glycosylated. HdCorfS6 transcripts appear to be abundant in lepidopteran host hemocytes compared to the other tissues analyzed. The second gene described, HdGorfP30, is well expressed in hemocytes, but also in other tissues, such as the fat body, nervous system and epidermis. This gene is peculiar since it presents 17 perfectly conserved repeated sequences arranged in tandem arrays. Each of these repeats contains 58% of serine and threonine residues and therefore several potential sites for glycosylation. This mucin-like protein, predicted as highly glycosylated, could be involved in host immune suppression.
Collapse
Affiliation(s)
- L Galibert
- I.N.R.A., Laboratoire de Pathologie Comparée, UMR 5087 I.N.R.A./C.N.R.S./Université Montpellier II, 30380 St-Christol-les-Alès, France
| | | | | | | | | | | |
Collapse
|
13
|
Béliveau C, Levasseur A, Stoltz D, Cusson M. Three related TrIV genes: comparative sequence analysis and expression in host larvae and Cf-124T cells. JOURNAL OF INSECT PHYSIOLOGY 2003; 49:501-511. [PMID: 12770629 DOI: 10.1016/s0022-1910(03)00055-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report on the cloning and sequencing of two Tranosema rostrale ichnovirus (TrIV) genes, and assess their relatedness to TrV1, the gene encoding the most abundant TrIV transcript in last-instar Choristoneura fumiferana larvae parasitized by T. rostrale. One of the two newly isolated genes, TrV2, features an organization similar to that of TrV1, with one intron flanked by two exons; it encodes a 102 amino acid protein showing 79% similarity to TrV1. The third gene, TrV4, encodes a larger protein (143 aa) displaying similarity to the other two only over the first approximately 50 amino acid residues of its sequence; the remaining portion contains an imperfect octad repeat. Although the TrV4 gene contains only one exon, it has an intron similar in size and sequence to that of TrV1 and TrV2; in fact, the non-coding regions of all three genes show higher sequence identity than the coding regions, pointing to their common origin. Southern analysis suggests that each gene maps to a different TrIV genome segment, with homologous sequences apparently present on other segments. TrV1 and TrV4 transcription in penultimate (5th) instar hosts, parasitized shortly after the molt, was strong for both genes 1 and 2 days p.p., with transcript abundance decreasing after the final molt; thus, neither of these genes is upregulated during induction of developmental arrest in last-instar hosts. Cf-124T cells inoculated with T. rostrale calyx fluid showed significant levels of apoptosis 24-72 h p.i.; TrV1 was detected in the culture medium, suggesting that this and/or other TrIV-encoded proteins may be responsible for the observed cytopathic effect. Southern and Northern analyses, using DNA and RNA extracted from infected Cf-124T cells, revealed the presence of both TrV1- and TrV4-carrying genome segments and transcripts, but neither DNA, at least in episomal form, nor mRNA persisted for more than a few days p.i. This in vitro system may provide a suitable starting point for the study of TrIV gene functions.
Collapse
Affiliation(s)
- C Béliveau
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., P.O. Box 3800, Sainte-Foy, Quebec G1V 4C7, Canada
| | | | | | | |
Collapse
|
14
|
Volkoff AN, Béliveau C, Rocher J, Hilgarth R, Levasseur A, Duonor-Cérutti M, Cusson M, Webb BA. Evidence for a conserved polydnavirus gene family: ichnovirus homologs of the CsIV repeat element genes. Virology 2002; 300:316-31. [PMID: 12350362 DOI: 10.1006/viro.2002.1535] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
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.
Collapse
Affiliation(s)
- A-N Volkoff
- I.N.R.A., Laboratoire de Pathologie Comparée, UMR 5087 INRA/CNRS/Université de Montpellier II, 30380, St Christol-les-Alès, France.
| | | | | | | | | | | | | | | |
Collapse
|
15
|
|
16
|
Béliveau C, Laforge M, Cusson M, Bellemare G. Expression of a Tranosema rostrale polydnavirus gene in the spruce budworm, Choristoneura fumiferana. J Gen Virol 2000; 81:1871-80. [PMID: 10859395 DOI: 10.1099/0022-1317-81-7-1871] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The endoparasitic wasp Tranosema rostrale (Ichneumonidae) transmits a polydnavirus (PDV) to its host, Choristoneura fumiferana, during oviposition. Unlike most other PDVs examined, the virus of T. rostrale (TrPDV) does not appear to play an important role in suppressing the host cellular immune response. However, it inhibits host metamorphosis. In the present study, TrPDV gene expression was examined in parasitized and virus-injected last-instar caterpillars. Northern analysis with viral DNA as a probe revealed only one detectable mRNA, of about 650 bp. The corresponding cDNA, termed TrV1, was cloned and sequenced and found to encode a protein of 103 amino acids which, following cleavage of the putative signal peptide, has a predicted molecular mass of 9.3 kDa. This protein displays limited similarity to the VHv1.4 cysteine-rich protein from the PDV of Campoletis sonorensis, mostly within the signal peptide region. By using a TrV1-specific probe, the TrV1 gene was localized to segment G of the TrPDV genome. The cuticle and fat body were identified as the principal sites of TrV1 transcription, with little transcription observed in haemocytes and midgut. Western analysis of proteins extracted from selected tissues of parasitized insects suggested that the TrV1 protein is secreted in the haemolymph. As observed for other PDVs, injection of TrPDV did not suppress transcription of the gene that encodes juvenile hormone esterase, the activity of which is inhibited by the virus. We speculate that the TrV1 protein may play a role in the inhibition of C. fumiferana metamorphosis.
Collapse
Affiliation(s)
- C Béliveau
- Département de Biochimie, Pavillon Charles-Eugène-Marchand, Université Laval, Sainte-Foy, QC, Canada G1K 7P4
| | | | | | | |
Collapse
|
17
|
Cusson M, Laforge M, Miller D, Cloutier C, Stoltz D. Functional significance of parasitism-induced suppression of juvenile hormone esterase activity in developmentally delayed Choristoneura fumiferana larvae. Gen Comp Endocrinol 2000; 117:343-54. [PMID: 10764546 DOI: 10.1006/gcen.1999.7406] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
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.
Collapse
Affiliation(s)
- M Cusson
- Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Sainte-Foy, Québec, Canada.
| | | | | | | | | |
Collapse
|