Persistence and expression of Cotesia congregata polydnavirus in host larvae of the tobacco hornworm, Manduca sexta

Le, N. T., Asgari, S., Amaya, K., Tan, F. F. and Beckage, N. E. (2003) Persistence and expression of Cotesia congregata polydnavirus in host larvae of the tobacco hornworm, Manduca sexta. Journal of Insect Physiology, 49 5: Polydnaviruses of Insects: Evolution and Physiological Functions: 533-543. doi:10.1016/S0022-1910(03)00052-0


Author Le, N. T.
Asgari, S.
Amaya, K.
Tan, F. F.
Beckage, N. E.
Title Persistence and expression of Cotesia congregata polydnavirus in host larvae of the tobacco hornworm, Manduca sexta
Journal name Journal of Insect Physiology   Check publisher's open access policy
ISSN 0022-1910
Publication date 2003-05-01
Year available 2003
Sub-type Article (original research)
DOI 10.1016/S0022-1910(03)00052-0
Open Access Status Not yet assessed
Volume 49
Issue 5: Polydnaviruses of Insects: Evolution and Physiological Functions
Start page 533
End page 543
Total pages 11
Editor Nancy Beckage
Place of publication Oxford
Publisher Elsevier Science Ltd
Language eng
Abstract The gregarious braconid wasp Cotesia congregata parasitizes host larvae of Manduca sexta, and several other sphingid species. Parasitism induces host immunosuppression due to the disruptive action of the wasp's polydnavirus (PDV) on host blood cells. During the initial stages of parasitism, these cells undergo apoptosis followed by cell clumping, which clears the hemolymph of a large number of cells. In this study, the persistence and expression of Cotesia congregata PDV (CcPDV) were examined using Southern and Nor-them blots, respectively. Digoxygenin-labelled total polydnaviral DNA was used to probe genomic DNA isolated from fat body and brains of hosts with emerged wasps taken 6 days following egress of the parasitoids, and significant cross-hybridization between the host fat body genomic DNA with viral DNA was seen. Thus, the virus persists in the host for the duration of parasitism. even during the post-emergence period, and may even be integrated in the host caterpillar DNA. Viral gene expression was examined using Northern blots and probes to the Cotesia rubecula CrV1 homolog, and the CrV1-like mRNAs were expressed as early as 4 h post-parasitization for at least 72 h and faint hybrization is even seen at the time the wasps eclose. In contrast, in Pieris rapae larvae the CrV1 transcript is expressed only for a brief time, during which time hemocyte function is disrupted. The effect is transitory, and hemocytes regain their normal functions after the parasites emerge as first instars. The genome of CcPDV contains one copy of the CrV1-like homolog as shown on Southern blots of viral genomic DNA. In conjunction with our earlier studies of the PDV-encoded early protein 1, the current work suggests multiple viral transcripts are produced following parasitization of the host. and likely target host hemocytes to induce their apoptosis, thereby preventing encapsulation of the parasitoid's eggs. Whether viral DNAs are integrated in the host's genomic DNA remains to be proven, but our results provide preliminary evidence that viral DNAs are detected in the host's fat body cells examined at the time of wasp ernergence and several days later. (C) 2003 Elsevier Science Ltd. All rights reserved.
Keyword Entomology
Physiology
Parasitism Polydnavirus
Viral Gene Expression
Viral Gene Integration
Tobacco Hornworm
Manduca Sexta
Braconid Wasp
Chelonus-inanitus Braconidae
Pseudoplusia-includens
Microplitis-demolitor
Heliothis-virescens
Wasp
Dna
Protein
Venom
Chromosome
Hemolymph
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Biological Sciences Publications
 
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Created: Mon, 13 Aug 2007, 23:37:09 EST