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Ouvrages Année : 2012

Evolution and Origin of Polydnavirus Virulence Genes. In Symbionts and Pathogens

Résumé

Polydnaviruses (PDVs) have a unique life-cycle, comprised of a mutualistic lifestyle with their associated parasitoid wasps and a parasitic interaction with the lepidopteran wasp hosts. They are present as proviruses in the parasitoid wasps that harbor them. The female wasps produce particles that contain circular double-stranded DNA versions of the viruses that are injected into the wasps' lepidopteran hosts. This 'injected circular form' is replication deficient but is absolutely essential for the physiological regulation of caterpillars that leads to parasitoid survival. PDVs are divided into two genera, bracoviruses (BVs) and ichnoviruses (IVs) associated with tens of thousands of endoparasitoid braconid and ichneumonid wasps, respectively, belonging to the Ichneumonoidea superfamily. The absence of PDVs in basal lineages of Ichneumonoidea strongly suggests that the association of BVs with braconids and IVs with ichneumonids arose independently. In ichneumonids, PDVs have been identified in the Campopleginae and Banchinae subfamily. The unique genomic features of the first banchine virus examined to date also suggest they could have an origin distinct from those of IVs and BVs (Lapointe et al., 2007). The absence of genes involved in virus production in the injected circular form is likely to be a signature of the reductive evolution that these PDVs have been subjected to, due to their reliance on wasps for transmission and the absence of replication in host larvae. In this chapter, we will focus on the PDV circular genomes that are injected into the lepidopteran hosts and highlight how selection pressures are likely to have modeled their content, organization, gene function, and efficiency. These PDV genomes are atypical for viruses in the sense that they harbor numerous genes, many of which
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Dates et versions

hal-00769220 , version 1 (29-12-2012)

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Citer

Elisabeth Huguet, Céline Serbielle, Sébastien Moreau. Evolution and Origin of Polydnavirus Virulence Genes. In Symbionts and Pathogens. Elsevier, Eds Beckage and J-M Drezen, San Diego, USA., pp.63-78, 2012, ⟨10.1016/B978-0-12-384858-1.00005-9⟩. ⟨hal-00769220⟩
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