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Isolation and characterization of a baculovirus associated with the insect parasitoid wasp, Cotesia marginiventris, or its host, Trichoplusia ni.

ABSTRACT: A multiple nucleopolyhedrovirus (MNPV) was isolated from Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) larvae that had been stung by the parasitoid Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae). The wild type virus was plaque purified by infecting a Heliothis subflexa (BCIRL- HsAM1) cell line and isolating several clones. The mean estimated genomic size of this virus based on PstI, BstEII, StyI, HindIII restriction profiles was estimated to be 106 +/- 2.5 kbp (mean+/-SE). A clone designated as TnMNPV/CmBCL9 was used in bioassays against several lepidopteran pests and in comparative studies with the baculoviruses AcMNPV, AgMNPV, AfMNPV, PxMNPV and HzSNPV of Autographa califomica, Anticarsia gemmatalis, Anagrapha falcifera, Plutella xylostella, and Helicoverpa zea, respectively. Infectivity studies showed that TnMNPV/CmBCL9 was highly infectious for Heliothis subflexa and T. ni, with an LC(50) value 0.07 occlusion bodies/mm(2) in both species and also infectious for H. zea and Heliothis virescens with LC(50) values of 0.22 and 0.27 occlusion bodies/mm(2), respectively. Restriction endonuclease analysis of the isolate and selected baculoviruses revealed profiles that were very similar to AfMNPV but different from the restriction endonuclease profiles of the other baculoviruses. Hybridization studies suggest that the TnMNPV/CmBCL9 was closely related to AfMNPV and AcMNPV-HPP. Further support for this comes from a phylogenetic analysis employing a split-graphs network, comparing the polh, egt, and p10 genes from TnMNPV/CmBCL9 with those from other baculoviruses and suggests that this virus is closely related to the AcMNPV variants, AfMNPV and RoMNPV of Rachiplusia ou.

SUBMITTER: Grasela JJ

PROVIDER: S-EPMC3127397 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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Isolation and characterization of a baculovirus associated with the insect parasitoid wasp, Cotesia marginiventris, or its host, Trichoplusia ni.

Grasela James J JJ McIntosh Arthur H AH Shelby Kent S KS Long Steve S

Journal of insect science (Online) 20080101

A multiple nucleopolyhedrovirus (MNPV) was isolated from Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) larvae that had been stung by the parasitoid Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae). The wild type virus was plaque purified by infecting a Heliothis subflexa (BCIRL- HsAM1) cell line and isolating several clones. The mean estimated genomic size of this virus based on PstI, BstEII, StyI, HindIII restriction profiles was estimated to be 106 +/- 2.5 kbp (mean+/-SE). A clon ...[more]

PMID: 20334593

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Project description:UnlabelledProductive infection of Trichoplusia ni cells by the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) leads to expression of ~156 viral genes and results in dramatic cell remodeling. How the cell transcriptome responds to viral infection was unknown due to the lack of a reference genome and transcriptome for T. ni. We used an ~60-Gb RNA sequencing (RNA-seq) data set from infected and uninfected T. ni cells to generate and annotate a de novo transcriptome assembly of approximately 70,322 T. ni unigenes (assembled transcripts), representing the 48-h infection cycle. Using differential gene expression analysis, we found that the majority of host transcripts were downregulated after 6 h postinfection (p.i.) and throughout the remainder of the infection. In contrast, 5.7% (4,028) of the T. ni unigenes were upregulated during the early period (0 to 6 h p.i.), followed by a decrease through the remainder of the infection cycle. Also, a small subset of genes related to metabolism and stress response showed a significant elevation of transcript levels at 18 and 24 h p.i. but a decrease thereafter. We also examined the responses of genes belonging to a number of specific pathways of interest, including stress responses, apoptosis, immunity, and protein trafficking. We identified specific pathway members that were upregulated during the early phase of the infection. Combined with the parallel analysis of AcMNPV expression, these results provide both a broad and a detailed view of how baculovirus infection impacts the host cell transcriptome to evade cellular defensive responses, to modify cellular biosynthetic pathways, and to remodel cell structure.ImportanceBaculoviruses are insect-specific DNA viruses that are highly pathogenic to their insect hosts. In addition to their use for biological control of certain insects, baculoviruses also serve as viral vectors for numerous biotechnological applications, such as mammalian cell transduction and protein expression for vaccine production. While there is considerable information regarding viral gene expression in infected cells, little is known regarding responses of the host cell to baculovirus infection. In these studies, we assembled a cell transcriptome from the host Trichoplusia ni and used that transcriptome to analyze changes in host cell gene expression throughout the infection cycle. The study was performed in parallel with a prior study of changes in viral gene expression. Combined, these studies provide an unprecedented new level of detail and an overview of events in the infection cycle, and they will stimulate new experimental approaches to understand, modify, and utilize baculoviruses for a variety of applications.

Project description:The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a large double-stranded DNA (dsDNA) virus that encodes approximately 156 genes and is highly pathogenic to a variety of larval lepidopteran insects in nature. Oral infection of larval midgut cells is initiated by the occlusion-derived virus (ODV), while secondary infection of other tissues is mediated by the budded virus (BV). Global viral gene expression has been studied in detail in BV-infected cell cultures, but studies of ODV infection in the larval midgut are limited. In this study, we examined expression of the ∼156 AcMNPV genes in Trichoplusia ni midgut tissue using a transcriptomic approach. We analyzed expression profiles of viral genes in the midgut and compared them with profiles from a T. ni cell line (Tnms42). Several viral genes (p6.9, orf76, orf75, pp31, Ac-bro, odv-e25, and odv-ec27) had high expression levels in the midgut throughout the infection. Also, the expression of genes associated with occlusion bodies (polh and p10) appeared to be delayed in the midgut in comparison with the cell line. Comparisons of viral gene expression profiles revealed remarkable similarities between the midgut and cell line for most genes, although substantial differences were observed for some viral genes. These included genes associated with high level BV production (fp-25k), acceleration of systemic infection (v-fgf), and enhancement of viral movement (arif-1/orf20). These differential expression patterns appear to represent specific adaptations for virus infection and transmission through the polarized cells of the lepidopteran midgut.IMPORTANCE Baculoviruses such as AcMNPV are pathogens that are natural regulators of certain insect populations. Baculovirus infections are biphasic, with a primary phase initiated by oral infection of midgut epithelial cells by occlusion-derived virus (ODV) virions and a secondary phase in which other tissues are infected by budded-virus (BV) virions. While AcMNPV infections in cultured cells have been studied extensively, comparatively little is known regarding primary infection in the midgut. In these studies, we identified gene expression patterns associated with ODV-mediated infection of the midgut in Trichoplusia ni and compared those results with prior results from BV-infected cultured cells, which simulate secondary infection. These studies provide a detailed analysis of viral gene expression patterns in the midgut, which likely represent specific viral strategies to (i) overcome or avoid host defenses in the gut and (ii) rapidly move infection from the midgut, into the hemocoel to facilitate systemic infection.

Project description:BackgroundA fundamental feature of parasitism is the nutritional exploitation of host organisms by their parasites. Parasitoid wasps lay eggs on arthropod hosts, exploiting them for nutrition to support larval development by using diverse effectors aimed at regulating host metabolism. However, the genetic components and molecular mechanisms at the basis of such exploitation, especially the utilization of host amino acid resources, remain largely unknown. To address this question, here, we present a chromosome-level genome assembly of the parasitoid wasp Cotesia chilonis and reconstruct its amino acid biosynthetic pathway.ResultsAnalyses of the amino acid synthetic pathway indicate that C. chilonis lost the ability to synthesize ten amino acids, which was confirmed by feeding experiments with amino acid-depleted media. Of the ten pathways, nine are known to have been lost in the common ancestor of animals. We find that the ability to synthesize arginine was also lost in C. chilonis because of the absence of two key genes in the arginine synthesis pathway. Further analyses of the genomes of 72 arthropods species show that the loss of arginine synthesis is common in arthropods. Metabolomic analyses by UPLC-MS/MS reveal that the temporal concentrations of arginine, serine, tyrosine, and alanine are significantly higher in host (Chilo suppressalis) hemolymph at 3 days after parasitism, whereas the temporal levels of 5-hydroxylysine, glutamic acid, methionine, and lysine are significantly lower. We sequence the transcriptomes of a parasitized host and non-parasitized control. Differential gene expression analyses using these transcriptomes indicate that parasitoid wasps inhibit amino acid utilization and activate protein degradation in the host, likely resulting in the increase of amino acid content in host hemolymph.ConclusionsWe sequenced the genome of a parasitoid wasp, C. chilonis, and revealed the features of trait loss in amino acid biosynthesis. Our work provides new insights into amino acid exploitation by parasitoid wasps, and this knowledge can specifically be used to design parasitoid artificial diets that potentially benefit mass rearing of parasitoids for pest control.

Dataset Information

Isolation and characterization of a baculovirus associated with the insect parasitoid wasp, Cotesia marginiventris, or its host, Trichoplusia ni.

Publications

Isolation and characterization of a baculovirus associated with the insect parasitoid wasp, Cotesia marginiventris, or its host, Trichoplusia ni.

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