The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Bruce A. Webb - One of the best experts on this subject based on the ideXlab platform.
-
2002. Characterization of Campoletis Sonorensis ichnovirus segment I genes Int
2016Co-Authors: S. Hilgarth, Bruce A. WebbAbstract:Campoletis Sonorensis ichnovirus (CsIV) is a symbiotic virus associated with the endoparasitic wasp C. Sonorensis. The virus is injected into the wasp’s host, Heliothis virescens, during oviposition. One CsIV gene has been identified as a repeat element (rep) gene and encodes a ubiquitous imperfectly conserved 540 bp sequence. We report the sequencing and mapping of a rep-containing segment, segment I, that hybridizes to a known rep sequence from segment O1. Analysis of this 8–6 kbp segment identified three ORFs having high similarity to the 540 bp rep sequence. All three rep sequence ORFs were expressed in parasitized H. virescens as well as in C. Sonorensis tissues. Two of these rep genes, I 0.9 and I 1.1, have single copies of the 540 bp repeat sequence, while the third rep gene, I 1.2, has two imperfect copies, which are more similar to each other than to sequences on the segment I single-motif genes. Like the CsIV BHv 0.9 rep gene, the segment I rep genes lack introns and a signal peptide, suggesting that they are not secreted. Based on their similarity in nucleotide sequence, predicted amino acid sequence and gene structure, the three segment I repeat-containing genes, I 0.9, I 1.1 and I 1.2, are new members of the rep gene family
-
analysis of gene transcription and relative abundance of the cys motif gene family from Campoletis Sonorensis ichnovirus csiv and further characterization of the most abundant cys motif protein whv1 6
Insect Molecular Biology, 2013Co-Authors: Torrence A Gill, Bruce A. WebbAbstract:The cys-motif gene family associated with Campoletis Sonorensis ichnovirus contains 10 members, WHv1.6, WHv1.0, VHv1.1, VHv1.4, AHv1.0, A'Hv0.8, FHv1.4, LHv2.8, UHv0.8, and UHv0.8a. The results of this study indicated that, within the encapsidated virion, WHv1.6 is the most abundant cys-motif gene, while the combined AHv genes are the least abundant. During parasitization of Heliothis virescens by Campoletis sonorenis, WHv1.6 transcripts were the mostly highly expressed, while the combined UHv genes had the lowest expression. Further proteomic analysis of WHv1.6 showed that it accumulates at high levels in parasitized plasma by 6 h, and is detectable in the haemocytes, fat body, malpighian tubules, nerve cord and epidermis by 2 days after parasitization. Localization experiments led us to conclude that WHv1.6 interacts with the cell membrane along with other organelles within a virus-infected cell and prevents immunocytes from spreading or adhering to a foreign surface. Similarly to VHv1.4 and VHv1.1, WHv1.6 is able to inhibit the translation of haemocyte and Malpighian tubule RNAs. Our results showed that the expression of cys-motif genes during parasitization is related to the gene copy number of each gene within the encapsidated virion and may also be dependent upon cis-regulatory element activity in different target tissues. In addition, WHv1.6 plays a major role in inhibiting the cellular encapsulation response by H. virescens.
-
Journal of Insect
2013Co-Authors: Matthew W Turnbull, Stacy B Martin, Bruce A. WebbAbstract:insectscience.org Quantitative analysis of hemocyte morphological abnormalities associated with Campoletis Sonorensis parasitizatio
-
the Campoletis Sonorensis ichnovirus vankyrin protein p vank 1 inhibits apoptosis in insect sf9 cells
Insect Molecular Biology, 2009Co-Authors: Angelika Fathgoodin, Jeremy A Kroemer, Bruce A. WebbAbstract:: The Campoletis Sonorensis ichnovirus (CsIV) vankyrin genes encode proteins containing truncated ankyrin repeat domains with sequence homology to the inhibitory domains of NF-kappaB transcription factor inhibitors, IkappaBs. The CsIV vankyrin proteins are thought to be involved in the suppression of NF-kappaB activity during immune response and/or developmental events in the parasitized host. Here we report that when P-vank-1 was expressed stably from Sf9 cells, prolonged survival of these cells was observed after baculovirus infection, UV irradiation, and treatment with the apoptosis-inducing chemical camptothecin compared to untransformed Sf9 cells. Furthermore, P-vank-1 inhibited nuclear and internucleosomal degradation and caspase activity after induction of apoptosis in Sf9 cells stably expressing P-vank-1. This is the first report of a polydnavirus protein with anti-apoptotic function.
-
Divergences in protein activity and cellular localization within the Campoletis Sonorensis Ichnovirus Vankyrin family.
Journal of virology, 2006Co-Authors: Jeremy A Kroemer, Bruce A. WebbAbstract:Ichnoviruses (IVs) occur in obligate symbiotic associations with endoparasitic ichneumonid wasps. IVs are injected with eggs during parasitization, where viral infection and gene expression alter host physiology to ensure endoparasitoid survival. The seven Campoletis Sonorensis IV (CsIV) vankyrin genes encode proteins that possess ankyrin repeat domains resembling the inhibitory domains of NF-κB transcription factor inhibitors (IκBs). The CsIV vankyrins are divided into two subclasses: those expressed primarily in the host fat body (three genes) and those expressed in host hemocytes (four genes). CsIV vankyrin proteins showed limited antigenic similarity when analyzed by Western blotting. Cellular localization and expression patterns of recombinant vankyrin proteins in High Five and Sf9 insect cells differed within and between the subclasses and in cells exposed to lipopolysaccharide, laminarin, or viral immune challenge. In unstimulated Sf9 cells, five vankyrins were detected in cell nuclei. The remaining two proteins localized predominantly to cytoplasmic granules. Immune stimulation of cells resulted in a nuclear-to-cytoplasmic shift of three vankyrins but did not affect localization of other variants. When expressed from recombinant Autographa californica multiple nucleopolyhedroviruses (AcMNPVs), all vankyrins showed a nuclear localization during early stages of infection with patterns resembling those of immune-challenged cells as the infection progressed. Two fat body vankyrins also produced unique biological effects when expressed from recombinant AcMNPV. Insect cells infected with these viruses exhibited enhanced longevity compared to those infected with viruses expressing other vankyrins. Together, these data suggest that vankyrin proteins in CsIV have divergent physiological functions.
S B Vinson - One of the best experts on this subject based on the ideXlab platform.
-
Stage-specific effects of Campoletis Sonorensis parasitism on Heliothis virescens development and prothoracic glands.
Physiological Entomology, 2008Co-Authors: B A Dover, S B VinsonAbstract:The ichneumonid endoparasitoid Campoletis Sonorensis Cameron (Hymenoptera: Ichneumonidae) injects a polydnavirus when it oviposits into a host. We compared the development of Heliothis virescens (F.) (Lepidoptera: Noctuidae) larvae parasitized in the penultimate (fourth) stadium with those parasitized in the last (fifth) stadium by C.Sonorensis and show that hosts stung in the fifth stadium exhibited arrested or delayed development compared to the controls. Parasitoids developed normally to the point of emergence in larvae stung in the fifth stadium but most did not successfully emerge from the host. The prothoracic glands in all successfully parasitized fifth stadium hosts and most unsuccessfully parasitized fifth stadium hosts showed some degree of virally-induced degeneration. Larvae stung in the fourth stadium developed more slowly than controls and either did not moult or developed to a fifth and sometimes a supernumerary sixth stadium before parasitoid emergence. Unsuccessfully parasitized hosts were delayed in their development but eventually moulted to the fifth and, in some cases, a supernumerary sixth stadium before pupating. Hosts stung in the fourth stadium showed no signs of prothoracic gland degeneration whether successfully parasitized or not. In addition, calyx fluid injections into early fourth stadium hosts did not cause prothoracic gland degeneration even after these hosts moulted to the fifth stadium, suggesting that degeneration induced by polydnavirus is specific to the last stadium of the host.
-
The in vitro development from egg to prepupa of Campoletis Sonorensis (Hymenoptera: Ichneumonidae) in an artificial medium: importance of physical factors.
Journal of insect physiology, 1998Co-Authors: S B VinsonAbstract:A further attempt to improve the in vitro rearing of the solitary larval endoparasitoid Campoletis Sonorensis (Hymenoptera: Ichneumonidae) was made after third instars were obtained in previous studies. Respiration was an important factor for the parasitoid's continued development: both small diet volumes that exposed the larval cuticle to air and O(2)greatly improved growth and development of C. Sonorensis. Fifth instars were obtained when the parasitoid larvae were reared in medium volumes of 0.25ml and 0.1ml per well. Increasing the O(2) tension of the air resulted in larger larvae and prepupae. The agar layer under the nutritional medium was designed to slowly remove water from the diet. The results indicated that a drier environment was important for the parasitoid at the terminal stage. One percent and 0.8% agar gels, which removed water from the diet more rapidly, provided a drier environment and resulted in improved larval growth compared to the 0.6% agar gel. The detrimental effect of higher concentration of chicken egg yolk mixed in the diet was eliminated by using a dry egg yolk layer covered by an agar layer. This sandwich technique resulted in more parasitoid larvae molting to the final larval instar (5th) and the formation of many prepupae. However, the development of prepupae was premature and none of the fifth instar larvae successfully formed a normal cocoon.
-
in vitro rearing of Campoletis Sonorensis a larval endoparasitoid of heliothis virescens from egg to third instar in an artificial medium devoid of insect sources
Entomologia Experimentalis Et Applicata, 1997Co-Authors: J S Hu, S B VinsonAbstract:Campoletis Sonorensis is a solitary larval endoparasitoid of several Heliothis spp. pests. This study was carried out to develop media devoid of insect sources for in vitro rearing the parasitoid. Trehalose, lysine, threonine, asparagine, glutamine, hydroxyproline, serine, bovine serum albumin, and lactalbumin were beneficial to C. Sonorensis. Addition of fresh chicken egg yolk at a low level improved the artificial media. Addition of 20-hydroxyecdysone increased the molting rate, reduced the critical size at molt and decreased development time. Parasitoid development in vitro was dependent on eggs that had been in the host for at least 22 h. Luminosity was also critical for the development of C. Sonorensis in vitro. Optimal development occurred in a L14:D10 photoperiod at 43 Lux light intensity. Utilizing the best media and conditions, 100% of the parasitoid larvae reached the second instar and over 37% molted to the third instar. However, no further development occurred.
-
Stadium-specific degeneration of host prothoracic glands by Campoletis Sonorensis calyx fluid and its association with host ecdysteroid titers.
Journal of Insect Physiology, 1995Co-Authors: B A Dover, Toshiharu Tanaka, S B VinsonAbstract:Abstract Campoletis Sonorensis is a polydnavirus-carrying wasp that parasitizes Heliothis virescens larvae. Previous studies indicated that C. Sonorensis polydnavirus (CsPDV) induces degeneration of host prothoracic glands when injected into last-stadium hosts. Degeneration also occurs when last instars are naturally parasitized, but it is not observed in hosts parasitized as penultimate instars. This study investigated the effect of CsPDV on the development of penultimate-stadium hosts and the temporal sensitivity of H. virescens prothoracic glands to virally-induced degeneration. We found that calyx fluid (containing CsPDV) caused degeneration of host prothoracic glands when injected into newly-ecdysed, penultimate-stadium hosts, but degeneration was delayed until injected larvae reached the critical head capsule size for the last stadium, even when injected larvae exhibited supernumerary molts. Host prothoracic glands became sensitive to virally-induced gland degeneration just prior to apolysis to the last larval larval molt , simultaneous with an ecdysteroid peak. Prothoracic gland degeneration in response to calyx fluid was also noted in two other hosts of C. Sonorensis , Helicoverpa zea and Spodoptera exiguae .
-
stimuli influencing host microhabitat location in the parasitoid Campoletis Sonorensis
Entomologia Experimentalis Et Applicata, 1991Co-Authors: Heather J. Mcauslane, S B VinsonAbstract:The host microhabitat location behavior of females of the generalist parasitoid Campoletis Sonorensis (Cameron) (Hymenoptera: Ichneumonidae) was studied in a wind tunnel. Visual cues associated with the host plant cotton, Gossypium hirsutum L., were important and significantly more parasitoids completed flights to a damaged 4-leaf cotton plant bearing a Heliothis virescens (F.) (Lepidoptera: Noctuidae) larva and frass than to a similarly damaged single leaf with frass and a larva. This difference in completed flights was not due to differences in amounts of volatiles released by the two stimuli, Both naive and experienced parasitoids responded differently to an undamaged cotton leaf, a mechanically damaged leaf, a naturally damaged leaf with the host removed and a naturally damaged leaf with a host larva. Parasitoids completed significantly fewer flights to the undamaged sources of volatiles than to damaged sources of volatiles. Experienced females responded strongly to all types of damage. The number of flights completed by naive females to the three types of damage differed but not significantly and was less than the number completed by experienced females. Components of the preflight experience were varied to determine which factors were responsible for the higher response of experienced females to the host/plant complex. Oviposition was the most important component of this experience. Contact with host frass or plant damage followed by oviposition did not increase the response over that exhibited by females allowed oviposition only. When frass or damaged plant material were contacted without subsequent oviposition, females completed fewer flights than naive females.
Jeremy A Kroemer - One of the best experts on this subject based on the ideXlab platform.
-
the Campoletis Sonorensis ichnovirus vankyrin protein p vank 1 inhibits apoptosis in insect sf9 cells
Insect Molecular Biology, 2009Co-Authors: Angelika Fathgoodin, Jeremy A Kroemer, Bruce A. WebbAbstract:: The Campoletis Sonorensis ichnovirus (CsIV) vankyrin genes encode proteins containing truncated ankyrin repeat domains with sequence homology to the inhibitory domains of NF-kappaB transcription factor inhibitors, IkappaBs. The CsIV vankyrin proteins are thought to be involved in the suppression of NF-kappaB activity during immune response and/or developmental events in the parasitized host. Here we report that when P-vank-1 was expressed stably from Sf9 cells, prolonged survival of these cells was observed after baculovirus infection, UV irradiation, and treatment with the apoptosis-inducing chemical camptothecin compared to untransformed Sf9 cells. Furthermore, P-vank-1 inhibited nuclear and internucleosomal degradation and caspase activity after induction of apoptosis in Sf9 cells stably expressing P-vank-1. This is the first report of a polydnavirus protein with anti-apoptotic function.
-
Divergences in protein activity and cellular localization within the Campoletis Sonorensis Ichnovirus Vankyrin family.
Journal of virology, 2006Co-Authors: Jeremy A Kroemer, Bruce A. WebbAbstract:Ichnoviruses (IVs) occur in obligate symbiotic associations with endoparasitic ichneumonid wasps. IVs are injected with eggs during parasitization, where viral infection and gene expression alter host physiology to ensure endoparasitoid survival. The seven Campoletis Sonorensis IV (CsIV) vankyrin genes encode proteins that possess ankyrin repeat domains resembling the inhibitory domains of NF-κB transcription factor inhibitors (IκBs). The CsIV vankyrins are divided into two subclasses: those expressed primarily in the host fat body (three genes) and those expressed in host hemocytes (four genes). CsIV vankyrin proteins showed limited antigenic similarity when analyzed by Western blotting. Cellular localization and expression patterns of recombinant vankyrin proteins in High Five and Sf9 insect cells differed within and between the subclasses and in cells exposed to lipopolysaccharide, laminarin, or viral immune challenge. In unstimulated Sf9 cells, five vankyrins were detected in cell nuclei. The remaining two proteins localized predominantly to cytoplasmic granules. Immune stimulation of cells resulted in a nuclear-to-cytoplasmic shift of three vankyrins but did not affect localization of other variants. When expressed from recombinant Autographa californica multiple nucleopolyhedroviruses (AcMNPVs), all vankyrins showed a nuclear localization during early stages of infection with patterns resembling those of immune-challenged cells as the infection progressed. Two fat body vankyrins also produced unique biological effects when expressed from recombinant AcMNPV. Insect cells infected with these viruses exhibited enhanced longevity compared to those infected with viruses expressing other vankyrins. Together, these data suggest that vankyrin proteins in CsIV have divergent physiological functions.
-
Iκβ-Related vankyrin Genes in the Campoletis Sonorensis Ichnovirus: Temporal and Tissue-Specific Patterns of Expression in Parasitized Heliothis virescens Lepidopteran Hosts
Journal of virology, 2005Co-Authors: Jeremy A Kroemer, Bruce A. WebbAbstract:Polydnaviruses (PDVs) are unusual insect viruses that occur in obligate symbiotic associations with parasitic ichneumonid (ichnoviruses, or IVs) and braconid (bracoviruses, or BVs) wasps. PDVs are injected with eggs, ovarian proteins, and venom during parasitization. Following infection of cells in host tissues, viral genes are expressed and their products function to alter lepidopteran host physiology, enabling endoparasitoid development. Here we describe the Campoletis Sonorensis IV viral ankyrin (vankyrin) gene family and its transcription. The seven members of this gene family possess ankyrin repeat domains that resemble the inhibitory domains of the Drosophila melanogaster NF-κβ transcription factor inhibitor (Iκβ) cactus. vankyrin gene expression is detected within 2 to 4 h postparasitization (p.p.) in Heliothis virescens hosts and reaches peak levels by 3 days p.p. Our data indicate that vankyrin genes from the C. Sonorensis IV genome are differentially expressed in the tissues of parasitized hosts and can be divided into two subclasses: those that target the host fat body and those that target host hemocytes. Polyclonal antibodies raised against a fat-body targeting vankyrin detected a 19-kDa protein in crude extracts prepared from the 3 days p.p. fat body. Vankyrin-specific Abs localized to 3-day p.p. fat-body and hemocyte nuclei, suggesting a role for vankyrin proteins in the nuclei of C. Sonorensis IV-infected cells. These data are evidence for divergent tissue specificities and targeting of multigene families in IVs. We hypothesize that PDV vankyrin genes may suppress NF-κβ activity during immune responses and developmental cascades in parasitized lepidopteran hosts of C. Sonorensis.
Liwang Cui - One of the best experts on this subject based on the ideXlab platform.
-
Relationships between polydnavirus gene expression and host range of the parasitoid wasp Campoletis Sonorensis.
Journal of insect physiology, 2000Co-Authors: Liwang Cui, Ana I. Soldevila, Bruce A. WebbAbstract:To evaluate the relationship between immune suppression and host range six lepidopteran species were parasitized by the ichneumonid parasitoid Campoletis Sonorensis. Parasitism inhibited the growth of permissive hosts (Heliothis virescens, Helicoverpa zea, and Trichoplusia ni), whereas growth of semi-permissive (Spodoptera exigua, Agrotis ipsilon) and non-permissive hosts (Manduca sexta) was not significantly affected. The 29-36 kDa ovarian protein (OP), responsible for transient immunosuppression in the permissive host H. virescens, bound to and was endocytosed by hemocytes of permissive and non-permissive hosts. Expression of the cysteine-rich polydnavirus gene, VHv1.4, was detected in all the hosts, but declined only in semi- and non-permissive hosts at later times after parasitization. The VHv1.4 protein bound to hemocytes of permissive and semi-permissive hosts, but did not bind to hemocytes of the non-permissive host, M. sexta. Melanization of larval hemolymph was severely inhibited by parasitism in permissive hosts, but was unaffected in M. sexta. In the semi-permissive host, A. ipsilon, hemolymph melanization was transiently inhibited while viral genes were expressed. In conclusion, C. Sonorensis OP transiently inhibits encapsulation in all hosts that were tested. The host range of C. Sonorensis seems to be determined by whether or not the C. Sonorensis ichnovirus (CsIV) is able to establish persistent infections of parasitized larvae to provide long-term suppression of host immunity.
-
relationships between polydnavirus gene expression and host range of the parasitoid wasp Campoletis Sonorensis
Journal of Insect Physiology, 2000Co-Authors: Liwang Cui, Ana I. Soldevila, Bruce A. WebbAbstract:To evaluate the relationship between immune suppression and host range six lepidopteran species were parasitized by the ichneumonid parasitoid Campoletis Sonorensis. Parasitism inhibited the growth of permissive hosts (Heliothis virescens, Helicoverpa zea, and Trichoplusia ni), whereas growth of semi-permissive (Spodoptera exigua, Agrotis ipsilon) and non-permissive hosts (Manduca sexta) was not significantly affected. The 29‐36 kDa ovarian protein (OP), responsible for transient immunosuppression in the permissive host H. virescens, bound to and was endocytosed by hemocytes of permissive and non-permissive hosts. Expression of the cysteine-rich polydnavirus gene, VHv1.4, was detected in all the hosts, but declined only in semi- and non-permissive hosts at later times after parasitization. The VHv1.4 protein bound to hemocytes of permissive and semi-permissive hosts, but did not bind to hemocytes of the non-permissive host, M. sexta. Melanization of larval hemolymph was severely inhibited by parasitism in permissive hosts, but was unaffected in M. sexta. In the semi-permissive host, A. ipsilon, hemolymph melanization was transiently inhibited while viral genes were expressed. In conclusion, C. Sonorensis OP transiently inhibits encapsulation in all hosts that were tested. The host range of C. Sonorensis seems to be determined by whether or not the C. Sonorensis ichnovirus (CsIV) is able to establish persistent infections of parasitized larvae to provide long-term suppression of host immunity. © 2000 Elsevier Science Ltd. All rights reserved.
-
Expression and hemocyte-targeting of a Campoletis Sonorensis polydnavirus cysteine-rich gene in Heliothis virescens larvae.
Archives of insect biochemistry and physiology, 1997Co-Authors: Liwang Cui, Ana I. Soldevila, Bruce A. WebbAbstract:The polydnavirus associated with the parasitic wasp Campoletis Sonorensis is injected into the lepidopteran insect, Heliothis virescens, during parasitization, after which viral gene products suppress the cellular immune system of the hosts. Four related cysteine-rich polydnavirus gene have been identified in parasitized H. virescens larvae and grouped into a family. In this study, we investigated the expression and hemocyte targeting of the cysteine-rich VHv1.4 protein. Full-length and truncated VHv1.4 proteins were produced in a bacterial expression system, and the purified proteins were used to raise polyclonal antisera. In immunoblots the VHv1.4 protein was detected in parasitized insects as early as 6 h and throughout the entire course of parasitism. The VHv1.4 protein appeared predominantly in the plasma fraction of hemolymph from parasitized larvae, suggesting that this protein is secreted. The VHv1.4 protein expressed from a recombinant baculovirus was secreted in two lepidopteran cell lines and in larvae injected with the recombinant virus. Digestion with endoglycosidases suggests that the VHv1.4 protein is glycosylated at multiple N-glycosylation sites. Immunofluorescence assays showed that the VHv1.4 protein binds to the hemocytes, most notably the granulocytes, in H. virescens larvae. After binding, the VHv1.4 protein was internalized, probably by endocytosis. Specific binding of the VHv1.4 to granulocytes implies an important function in the suppression of host cellular encapsulation response.
-
Homologous sequences in the Campoletis Sonorensis polydnavirus genome are implicated in replication and nesting of the W segment family
1997Co-Authors: Liwang Cui, A. WebbAbstract:Polydnaviruses (PDVs) are double-stranded DNA viruses with segmented genomes that replicate only in the oviducts of some species of parasitic wasps and are required for the successful parasitization of lepidopteran insects. PDV DNA segments are integrated in the genomes of their associated wasp hosts, and some are nested; i.e., smaller segments are produced from and largely colinear with larger segments. To determine the internal structure of nested viral segments, the first complete nucleotide sequence of a PDV genome segment and its integration locus was determined. By restriction mapping, Southern blot, and sequence analyses, we demon-strated that the Campoletis Sonorensis PDV segment W is integrated into wasp genomic DNA. DNA sequence analysis revealed that proviral segment W terminates in two 1,185-bp direct long terminal repeats (LTRs) in the wasp chromosome, while only one LTR copy is present in the extrachromosomal (viral) W. The results suggest that terminal direct repeats are a general feature of PDV DNA segment integration but that the homology and size of the repeats can vary extensively. Segment W contains 12 imperfect direct repeats of six different types between 89 bp and 1.9 kbp with 65 to 90 % homology. The orientation and structure of the repeats suggest that W itself may have arisen through sequence duplication and subsequent divergence. Mapping, hybridization, and sequence analyses of cloned R and M demonstrated that these segments are nested within segment W and that internal imperfect direct repeats of one type are implicated in the homologous intramo
-
Homologous sequences in the Campoletis Sonorensis polydnavirus genome are implicated in replication and nesting of the W segment family.
Journal of virology, 1997Co-Authors: Liwang Cui, Bruce A. WebbAbstract:Polydnaviruses (PDVs) are double-stranded DNA viruses with segmented genomes that replicate only in the oviducts of some species of parasitic wasps and are required for the successful parasitization of lepidopteran insects. PDV DNA segments are integrated in the genomes of their associated wasp hosts, and some are nested; i.e., smaller segments are produced from and largely colinear with larger segments. To determine the internal structure of nested viral segments, the first complete nucleotide sequence of a PDV genome segment and its integration locus was determined. By restriction mapping, Southern blot, and sequence analyses, we demonstrated that the Campoletis Sonorensis PDV segment W is integrated into wasp genomic DNA. DNA sequence analysis revealed that proviral segment W terminates in two 1,185-bp direct long terminal repeats (LTRs) in the wasp chromosome, while only one LTR copy is present in the extrachromosomal (viral) W. The results suggest that terminal direct repeats are a general feature of PDV DNA segment integration but that the homology and size of the repeats can vary extensively. Segment W contains 12 imperfect direct repeats of six different types between 89 bp and 1.9 kbp with 65 to 90% homology. The orientation and structure of the repeats suggest that W itself may have arisen through sequence duplication and subsequent divergence. Mapping, hybridization, and sequence analyses of cloned R and M demonstrated that these segments are nested within segment W and that internal imperfect direct repeats of one type are implicated in the homologous intramolecular recombination events that generate segments R and M. Interestingly, segment nesting differentially increases the copy number of genes encoded by segment W, suggesting that the unusual genomic organization of PDVs may be directly linked to the unique functions of this virus in its obligate mutualistic association with parasitic wasps.
Pierre Franck - One of the best experts on this subject based on the ideXlab platform.
-
Population genetic structure of two primary parasitoids of Spodoptera frugiperda (Lepidoptera), Chelonus insularis and Campoletis Sonorensis (Hymenoptera): to what extent is the host plant important?
Molecular ecology, 2010Co-Authors: Violaine Jourdie, Nadir Alvarez, Ted C J Turlings, Trevor Williams, Jaime Molina-ochoa, David J. Bergvinson, Betty Benrey, Pierre FranckAbstract:Plant chemistry can strongly influence interactions between herbivores and their natural enemies, either by providing volatile compounds that serve as foraging cues for parasitoids or predators, or by affecting the quality of herbivores as hosts or prey. Through these effects plants may influence parasitoid population genetic structure. We tested for a possible specialization on specific crop plants in Chelonus insularis and Campoletis Sonorensis, two primary parasitoids of the fall armyworm, Spodoptera frugiperda. Throughout Mexico, S. frugiperda larvae were collected from their main host plants, maize and sorghum and parasitoids that emerged from the larvae were used for subsequent comparison by molecular analysis. Genetic variation at eight and 11 microsatellites were respectively assayed for C. insularis and C. Sonorensis to examine isolation by distance, host plant and regional effects. Kinship analyses were also performed to assess female migration among host-plants. The analyses showed considerable within population variation and revealed a significant regional effect. No effect of host plant on population structure of either of the two parasitoid species was found. Isolation by distance was observed at the individual level, but not at the population level. Kinship analyses revealed significantly more genetically related—or kin—individuals on the same plant species than on different plant species, suggesting that locally, mothers preferentially stay on the same plant species. Although the standard population genetics parameters showed no effect of plant species on population structure, the kinship analyses revealed that mothers exhibit plant species fidelity, which may speed up divergence if adaptation were to occur.
-
isolation and characterization of polymorphic microsatellite loci in two primary parasitoids of the noctuid spodoptera frugiperda chelonus insularis and Campoletis Sonorensis hymenoptera
Molecular Ecology Resources, 2009Co-Authors: Violaine Jourdie, Nadir Alvarez, Ted C J Turlings, Pierre FranckAbstract:Fifteen and 13 microsatellite loci were isolated, respectively, from Campoletis Sonorensis Cameron and from Chelonus insularis Cresson. These two parasitic Hymenoptera are primary parasitoids of Lepidoptera in North, Central and South America, including the important agricultural pest Spodoptera frugiperda. Allelic diversity and heterozygosity were quantified in samples from Mexico. Each locus was polymorphic, with the number of alleles ranging from two to 16 in C. Sonorensis and from four to 18 in C. insularis. Heterozygosity ranged from 0.088 to 0.403 in C. Sonorensis and from 0.106 to 0.458 in C. insularis.