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Figure 5 | BMC Evolutionary Biology

Figure 5

From: Molecular evidence for the evolution of ichnoviruses from ascoviruses by symbiogenesis

Figure 5

Hypothetical mechanism for the integration and evolution of ascovirus genomes in endoparasitic wasps. Schematic representation of the three-step process of symbiogenesis, and DNA rearrangements that putatively occurred in the germ line of the wasp ancestors in the Banchinae and Campopleginae lineages, from the integration of an ascoviral genome to the proviral ichnoviral genome. Sequences that originate from the ascovirus are in blue, those of the wasp host and its chromosomes are in pink. Genes of ascoviral origin are surrounded by a thin black or white line, depending on their final chromosomal location. Two solutions can account for the final chromosomal organisation of the proviral ichnovirus genome, monolocus or multilocus, since this question is not fully understood in either wasp lineage. More complex alternatives to this three-step process might also be proposed and would involve, for example, the complete de novo creation of a mono or multi locus proviral genome from the recruitment by recombination or transposition of ascoviral and host genes located elsewhere in the wasp chromosomes. This model for the chromosomal organization of proviral DNA in polydnaviruses is consistent with data recently published [58].

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