title: Bracovirus gene products are highly divergent from insect proteins.
abstract: Recently, several polydnavirus (PDV) genomes have been completely sequenced. The dsDNA circles enclosed in virus particles and injected by wasps into caterpillars appear to mainly encode virulence factors potentially involved in altering host immunity and/or development, thereby allowing the survival of the parasitoid larvae within the host tissues. Parasitoid wasps generally inject virulence factors produced in the venom gland. As PDV genomes are inherited vertically by wasps through a proviral form, wasp virulence genes may have been transferred to this chromosomal form, leading to their incorporation into virus particles. Indeed, many gene products from Cotesia congregata bracovirus (CcBV), such as PTPs, IkappaB-like, and cystatins, contain protein domains conserved in metazoans. Surprisingly however, CcBV virulence gene products are not more closely related to insect proteins than to human proteins. To determine whether the distance between CcBV and insect proteins is a specific feature of BV proteins or simply reflects a general high divergence of parasitoid wasp products, which might be due to parasitic lifestyle, we have analyzed the sequences of wasp genes obtained from a cDNA library. Wasp sequences having a high similarity with Apis mellifera genes involved in a variety of biological functions could be identified indicating that the high level of divergence observed for BV products is a hallmark of these viral proteins. We discuss how this divergence might be explained in the context of the current hypotheses on the origin and evolution of wasp-bracovirus associations.
authors.affiliation: Institut de Recherche sur la Biologie de l'Insecte, UMR CNRS 6035, Université F. Rabelais, Tours, France.
authors.forename: Annie
authors.initials: A
authors.lastname: Bézier
authors.forename: Juline
authors.initials: J
authors.lastname: Herbinière
authors.forename: Céline
authors.initials: C
authors.lastname: Serbielle
authors.forename: Jérome
authors.initials: J
authors.lastname: Lesobre
authors.forename: Patrick
authors.initials: P
authors.lastname: Wincker
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Huguet
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Drezen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016000:Cluster Analysis; D015891:Cystatins / Q000235:genetics; D019143:Evolution, Molecular; D015723:Gene Library; D014644:Genetic Variation; D051550:I-kappa B Kinase / Q000235:genetics; D019476:Insect Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D018071:Polydnaviridae / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014764:Viral Proteins / Q000235:genetics*; D037521:Virulence Factors / Q000235:genetics*; D014863:Wasps / Q000821:virology*
chemical_list: D015891:Cystatins; D019476:Insect Proteins; D014764:Viral Proteins; D037521:Virulence Factors; D051550:I-kappa B Kinase