title: Extensive transcription analysis of the Hyposoter didymator Ichnovirus genome in permissive and non-permissive lepidopteran host species.
abstract: Ichnoviruses are large dsDNA viruses that belong to the Polydnaviridae family. They are specifically associated with endoparasitic wasps of the family Ichneumonidae and essential for host parasitization by these wasps. We sequenced the Hyposoter didymator Ichnovirus (HdIV) encapsidated genome for further analysis of the transcription pattern of the entire set of HdIV genes following the parasitization of four different lepidopteran host species. The HdIV genome was found to consist of at least 50 circular dsDNA molecules, carrying 135 genes, 98 of which formed 18 gene families. The HdIV genome had general features typical of Ichnovirus (IV) genomes and closely resembled that of the IV carried by Hyposoter fugitivus. Subsequent transcriptomic analysis with Illumina technology during the course of Spodoptera frugiperda parasitization led to the identification of a small subset of less than 30 genes with high RPKM values in permissive hosts, consisting with these genes encoding crucial virulence proteins. Comparisons of HdIV expression profiles between host species revealed differences in transcript levels for given HdIV genes between two permissive hosts, S. frugiperda and Pseudoplusia includens. However, we found no evident intrafamily gene-specific transcription pattern consistent with the presence of multigenic families within IV genomes reflecting an ability of the wasps concerned to exploit different host species. Interestingly, in two non-permissive hosts, Mamestra brassiccae and Anticarsia gemmatalis (most of the parasitoid eggs were eliminated by the host cellular immune response), HdIV genes were generally less strongly transcribed than in permissive hosts. This suggests that successful parasitism is dependent on the expression of given HdIV genes exceeding a particular threshold value. These results raise questions about the mecanisms involved in regulating IV gene expression according to the nature of the lepidopteran host species encountered.
authors.affiliation: INRA - Université de Montpellier 2, Unité « Diversité, Génomes et Interactions Insectes-Microorganismes », Place Eugène Bataillon, CC101, Montpellier, France.
authors.forename: Tristan
authors.initials: T
authors.lastname: Dorémus
authors.affiliation: INRA - Université de Montpellier 2, Unité « Diversité, Génomes et Interactions Insectes-Microorganismes », Place Eugène Bataillon, CC101, Montpellier, France.
authors.forename: François
authors.initials: F
authors.lastname: Cousserans
authors.affiliation: France Génomique - Commissariat à l'Energie Atomique - Institut de Génomique, Génoscope, 2, Evry, France.
authors.forename: Gabor
authors.initials: G
authors.lastname: Gyapay
authors.affiliation: INRA - Université de Montpellier 2, Unité « Diversité, Génomes et Interactions Insectes-Microorganismes », Place Eugène Bataillon, CC101, Montpellier, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Jouan
authors.affiliation: Escola Superior de Agricultura Luiz de Queiroz - Universidade de Sao Paulo, Departamento de Entomologia e Acarologia, Laboratório de Interações em Insetos, Piracicaba, Sao Paulo, Brazil.
authors.forename: Patricia
authors.initials: P
authors.lastname: Milano
authors.affiliation: INRA - CNRS - Université Nice Sophia Antipolis, Institut Sophia Agrobiotech, Sophia Antipolis, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Wajnberg
authors.affiliation: INRA - Université de Montpellier 2, Unité « Diversité, Génomes et Interactions Insectes-Microorganismes », Place Eugène Bataillon, CC101, Montpellier, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Darboux
authors.affiliation: Escola Superior de Agricultura Luiz de Queiroz - Universidade de Sao Paulo, Departamento de Entomologia e Acarologia, Laboratório de Interações em Insetos, Piracicaba, Sao Paulo, Brazil.
authors.forename: Fernando Luis
authors.initials: FL
authors.lastname: Cônsoli
authors.affiliation: INRA - Université de Montpellier 2, Unité « Diversité, Génomes et Interactions Insectes-Microorganismes », Place Eugène Bataillon, CC101, Montpellier, France.
authors.forename: Anne-Nathalie
authors.initials: AN
authors.lastname: Volkoff
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D023061:Gene Order; D016679:Genome, Viral; D054884:Host-Pathogen Interactions; D007915:Lepidoptera / Q000821:virology*; D008969:Molecular Sequence Data; D018071:Polydnaviridae / Q000235:genetics*; D014158:Transcription, Genetic; D059467:Transcriptome; D056189:Viral Tropism