Thèse soutenue

Génome et facteurs de virulence d'un polydnavirus d'hyménoptère parasitoïde
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Auteur / Autrice : Bertille Provost
Direction : Jean-Michel DrezenÉlisabeth Huguet
Type : Thèse de doctorat
Discipline(s) : Sciences de la vie
Date : Soutenance en 2004
Etablissement(s) : Tours

Résumé

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The hymenoptera Cotesia congregata lays its eggs into its host, a caterpillar of the lepidoptera Manduca sexta and introduces bracovirus (CcBV) particles. The proteins encoded by viral genes expressed in the parasitized host play an essential role for succesful parasitism, leading to modifications of host physiology such as alteration of immunity and prewandering developmental arrest. The introduction of this thesis summarizes up-to-date knowledge about insect immunity and bracoviral genes potentially involved in host physiology control. Sequencing and genome analyses demonstrated that the CcBV genome is composed of 30 double-stranded DNA circles coding for 9 multigenic families comprising protein tyrosine phosphatases, cystatins and ankyrin motif containing proteins. The characterisation of the viral genes expressed in the host is a key step toward further identification of the role of each protein in host physiology alteration. Field inversion gel electrophoresis (FIGE) allowed to physically localize PTP genes on the viral genome. Their expression was analysed on different host tissues by a multiplex RT PCR method. Next, biochemical activity tests of 2 PTPs were performed. Globally, genes of the described families are expressed in the parasitized host and some proteins have the biochemical function predicted by their conserved domains, suggesting these proteins play a role in the host physiological modifications induces by parasitism.