Progress 09/15/01 to 09/30/04
Outputs
The Polydnaviridae is a unique family of viruses associated with parasitoid wasps whose hosts are other insects. Polydnaviruses (PDVs) only replicate in wasps but they infect and cause severe physiological alterations in hosts essential for survival of the immature parasitoid. Thus, a true mutualism exists between PDVs and wasps as viral transmission depends on parasitoid survival and parasitoid survival depends on viral infection of the host. Here we report the genome sequences of two PDVs from divergent parasitoid lineages, Campoletis sonorensis ichnovirus (CsIV) and Microplitis demolitor bracovirus (MdBV). CsIV and MdBV share several organizational and structural features including segmented genomes, virulence determinants that form gene families, extensive regions of non-coding sequence, and a lack of genes present in other viruses. However, CsIV and MdBV share no sequence homology with one another. We have also sequenced much of the genomes from Hyposoter
fugitivis (HfIV), Tranosema rostrale (TrIV) and Glypta fumiferana (GfIV). These polydnavirus sequences are being submitted to Genbank as annotations are completed with the MdBV, CsIV and HfIV genomes completely available at this time. The principle organizational paradigms of the overall polydnavirus genomes appear conserved. Viral gene families are a predominant feature. Only the viral ankyrin genes are evident in all polydnavirus genomes with other gene families differing between ichnovirus and bracovirus groups. The organization of the GfIV genome is distinctive and may indicate a novel origin for the Banchine viruses. Overall our data suggest the organizational similarities among polydnavirus genomes in ichneumonid and braconid wasps reflect convergent evolution driven by their alternately beneficial and pathogenic associations with insects.
Impacts
We expect to elucidate the relationships between genome organization and function. This may enable development of approaches to gene expression in diverse systems that utilize similar approaches to regulating gene expression We also expect to identify viral genes that disrupt insect physiology and the ways in which they are delivered to insects. Such genes could enable development of new methods of insect control.
Publications
- Kroemer, J.A. and Webb, B.A. 2005. Ikb-related vankyrin genes in the Campoletis sonorensis ichnovirus exhibit temporal and tissue-specific expression in parasitized Heliothis virescens lepidopteran hosts. Journal of Virology (in press)
- Webb, B.A., Beckage, N.E., Hayakawa, Y., Krell, P.J., Lanzrein, B., Strand, M.R., Stoltz, D.B. and Summers, M.D. 2004. Polydnaviridae. In: Virus Taxonomy. (C. Fauquet et al eds.) pp 253-259.
- Webb, B.A. and Strand, M.R. 2005. The Biology and Genomics of Polydnaviruses. Comparative Physiology and Biochemistry. In Comprehensive Molecular Insect Comprehensive Molecular Insect Science. Editors: Lawrence I. Gilbert, Kostas Iatrou and Sarjeet S. Gill Elsevier Press. Volume 5 pp 323-260.
- Kroemer, J.A. and Webb, B.A. 2004. Polydnavirus genes and genomes: emerging gene families and new insights into polydnavirus replication. Annual Review of Entomology 49:431-456.
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Progress 01/01/03 to 12/31/03
Outputs
Over the last year of this project we have focused on comparative analyses of the MdBV and CsIV genomes. This has been possible because of the completion of the Campoletis sonorensis ichnovirus genome and completion of the Microplitis croceipes bracovirus genomes (MdBV). We are also making significant progress in our analyses of the Hyposoter fugitives and Tranosema rostrale ichnoviruses and anticipate that we will complete sequence of these viruses in the coming year. We have initiated sequence of a fourth polydnavirus, the Glypta fumiferatus virus, but this is in its initial stages. We are noting broad themes in the organization of these polydnavirus genomes that are consistent with our hypothesis that the organization of these viruses results from convergent evolution within the constraints of the mutualism between polydnaviruses and parasitoids. We note that hypermolar segments typically encode gene families that have signal peptides while hypomolar segments
encode a different set of gene families that tend not to be secreted. Both polydnavirus groups encode a limited number of gene families (4 CsIV and 5 MdBV) with a sometimes large number of genes within a gene family (e.g. CsIV has 27 rep genes). The identities of some gene families suggests functional roles that we have begun to investigate. Many of these results should be published in the coming year.
Impacts
We expect to elucidate the relationships between genome organization and function. This may enable development of approaches to gene expression in diverse systems that utilize similar approaches to regulating gene expression We also expect to identify viral genes that disrupt insect physiology and the ways in which they are delivered to insects. Such genes could enable development of new methods of insect control.
Publications
- Rattanadechakul W and Webb B.A. (2003) Characterization of Campoletis sonorensis ichnovirus unique segment B and excision locus structure. J. Insect Physiol. 49:523-532.
- Galibert L., Barry P., Ravellec M., Webb B.A. Volkoff A.N. (2003) Update on the Hyposoter didymator ichnovirus genes expressed in the lepidopteran host: characterization of two novel genes J. Insect Physiol. 49:441-451.
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Progress 01/01/02 to 12/31/02
Outputs
This project entails complete sequence analysis of 4 polydnavirusm genomes. BRIEF SUMMARY OF PROGRESS: Milestones completed & anticipated: 1. Campoletis sonorensis ichnovirus sequence completed 1/1/02; annotation completed 9/1/02), all sequences submitted and released through Genbank by 9/1/02. 2. Microplitis croceipes bracovirus. Draft sequence completed 10/1/02, annotation in progress, sequences to be submitted and released through Genbank as annotation is completed. 3. Hyposoter fugitivis ichnovirus - draft sequence (12/15/02), finished sequence (ant. 3/1/03). 4. Tranosema rostrale ichnovirus - draft sequence in progress. Notable findings. Bracovirus genome segments are integrated at a single locus in wasp chromosomes so BAC cloning/sequencing strategy has been adopted as more effective. Bracovirus and ichnovirus genoms have similar features in that they are largely non-coding, encode multiple gene families and genes found on hypermolar DNA segments are highly
expressed. Both braco- and ichnoviruses encode genes related to NF-kb gene family of transcriptional regulators.
Impacts
We expect to identify genes that disrupt insect immunity, growth and development that are conserved among the various polydnavirus species. These genes may be used to develop novel means for insect control.
Publications
- No publications reported this period
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Progress 09/15/01 to 12/31/01
Outputs
This project will support the sequence analysis of 2 ichneumonid and 2 braconid polydnaviruses. We have acquired viral DNA from the ichnovirus, Hyposoter fugitivis, have constructed libraries and have sequenced over 50 kbp from this virus. We will acquire viral DNA from the Tranosema rostrale virus this summer as the insect is available only from June-August. Analyses of bracovirus genomes will also begin in the coming months.
Impacts
We expect to identify genes that may control insect growth and development and describe the genetic mechanisms through which viruses deliver these genes during parasitization.
Publications
- No publications reported this period
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