title: The mosaic genome structure of the Wolbachia wRi strain infecting Drosophila simulans.
abstract: The obligate intracellular bacterium Wolbachia pipientis infects around 20% of all insect species. It is maternally inherited and induces reproductive alterations of insect populations by male killing, feminization, parthenogenesis, or cytoplasmic incompatibility. Here, we present the 1,445,873-bp genome of W. pipientis strain wRi that induces very strong cytoplasmic incompatibility in its natural host Drosophila simulans. A comparison with the previously sequenced genome of W. pipientis strain wMel from Drosophila melanogaster identified 35 breakpoints associated with mobile elements and repeated sequences that are stable in Drosophila lines transinfected with wRi. Additionally, 450 genes with orthologs in wRi and wMel were sequenced from the W. pipientis strain wUni, responsible for the induction of parthenogenesis in the parasitoid wasp Muscidifurax uniraptor. The comparison of these A-group Wolbachia strains uncovered the most highly recombining intracellular bacterial genomes known to date. This was manifested in a 500-fold variation in sequence divergences at synonymous sites, with different genes and gene segments supporting different strain relationships. The substitution-frequency profile resembled that of Neisseria meningitidis, which is characterized by rampant intraspecies recombination, rather than that of Rickettsia, where genes mostly diverge by nucleotide substitutions. The data further revealed diversification of ankyrin repeat genes by short tandem duplications and provided examples of horizontal gene transfer across A- and B-group strains that infect D. simulans. These results suggest that the transmission dynamics of Wolbachia and the opportunity for coinfections have created a freely recombining intracellular bacterial community with mosaic genomes.
authors.affiliation: Department of Molecular Evolution, Evolutionary Biology Centre, Uppsala University, SE-752 36 Uppsala, Sweden.
authors.forename: Lisa
authors.initials: L
authors.lastname: Klasson
authors.forename: Joakim
authors.initials: J
authors.lastname: Westberg
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Sapountzis
authors.forename: Kristina
authors.initials: K
authors.lastname: Näslund
authors.forename: Ylva
authors.initials: Y
authors.lastname: Lutnaes
authors.forename: Alistair C
authors.initials: AC
authors.lastname: Darby
authors.forename: Zoe
authors.initials: Z
authors.lastname: Veneti
authors.forename: Lanming
authors.initials: L
authors.lastname: Chen
authors.forename: Henk R
authors.initials: HR
authors.lastname: Braig
authors.forename: Roger
authors.initials: R
authors.lastname: Garrett
authors.forename: Kostas
authors.initials: K
authors.lastname: Bourtzis
authors.forename: Siv G E
authors.initials: SG
authors.lastname: Andersson
mesh_terms: D000818:Animals; D017487:Ankyrins / Q000235:genetics; D004330:Drosophila / Q000382:microbiology*; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D016680:Genome, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D009030:Mosaicism; D011995:Recombination, Genetic; D020577:Wolbachia / Q000235:genetics*
chemical_list: D017487:Ankyrins