title: Palaeosymbiosis revealed by genomic fossils of Wolbachia in a strongyloidean nematode.
abstract: Wolbachia are common endosymbionts of terrestrial arthropods, and are also found in nematodes: the animal-parasitic filaria, and the plant-parasite Radopholus similis. Lateral transfer of Wolbachia DNA to the host genome is common. We generated a draft genome sequence for the strongyloidean nematode parasite Dictyocaulus viviparus, the cattle lungworm. In the assembly, we identified nearly 1 Mb of sequence with similarity to Wolbachia. The fragments were unlikely to derive from a live Wolbachia infection: most were short, and the genes were disabled through inactivating mutations. Many fragments were co-assembled with definitively nematode-derived sequence. We found limited evidence of expression of the Wolbachia-derived genes. The D. viviparus Wolbachia genes were most similar to filarial strains and strains from the host-promiscuous clade F. We conclude that D. viviparus was infected by Wolbachia in the past, and that clade F-like symbionts may have been the source of filarial Wolbachia infections.
authors.affiliation: Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Georgios
authors.initials: G
authors.lastname: Koutsovoulos
authors.affiliation: Institute of Infection and Global Health, The University of Liverpool, Liverpool, United Kingdom.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Makepeace
authors.affiliation: Institut de Recherche Agricole pour le Développement, Regional Centre of Wakwa, Ngaoundéré, Adamawa Region, Cameroon.
authors.forename: Vincent N
authors.initials: VN
authors.lastname: Tanya
authors.affiliation: Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Blaxter
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology / Q000469:parasitology; D004269:DNA, Bacterial / Q000235:genetics*; D016054:DNA, Protozoan / Q000235:genetics*; D004021:Dictyocaulus / Q000235:genetics* / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013559:Symbiosis; D020577:Wolbachia / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D016054:DNA, Protozoan