Presence of extensive Wolbachia symbiont insertions discovered in the genome of its host Glossina morsitans morsitans.

Corey Brelsfoard,Serap Aksoy,Uzma Alam,Peter Takac,Erich Telleria,Vangelis Doudoumis,Marco Falchetto,Francesca Scolari,Anna R Malacrida,Kostas Bourtzis,Martin Swain,George Tsiamis,Ludvik M Gomulski,Joshua B Benoit

doi:10.1371/journal.pntd.0002728

Abstract

Tsetse flies (Glossina spp.) are the cyclical vectors of Trypanosoma spp., which are unicellular parasites responsible for multiple diseases, including nagana in livestock and sleeping sickness in humans in Africa. Glossina species, including Glossina morsitans morsitans (Gmm), for which the Whole Genome Sequence (WGS) is now available, have established symbiotic associations with three endosymbionts: Wigglesworthia glossinidia, Sodalis glossinidius and Wolbachia pipientis (Wolbachia). The presence of Wolbachia in both natural and laboratory populations of Glossina species, including the presence of horizontal gene transfer (HGT) events in a laboratory colony of Gmm, has already been shown. We herein report on the draft genome sequence of the cytoplasmic Wolbachia endosymbiont (cytWol) associated with Gmm. By in silico and molecular and cytogenetic analysis, we discovered and validated the presence of multiple insertions of Wolbachia (chrWol) in the host Gmm genome. We identified at least two large insertions of chrWol, 527,507 and 484,123 bp in size, from Gmm WGS data. Southern hybridizations confirmed the presence of Wolbachia insertions in Gmm genome, and FISH revealed multiple insertions located on the two sex chromosomes (X and Y), as well as on the supernumerary B-chromosomes. We compare the chrWol insertions to the cytWol draft genome in an attempt to clarify the evolutionary history of the HGT events. We discuss our findings in light of the evolution of Wolbachia infections in the tsetse fly and their potential impacts on the control of tsetse populations and trypanosomiasis.

Highlights

The genus Wolbachia encompasses intracellular maternally inherited Gram-negative bacteria estimated to infect over 40% of insect species, in addition to filarial nematodes, crustaceans, and arachnids [1,2]
In this paper, which is being submitted as a satellite to the manuscript describing the Whole Genome Sequence (WGS) of the tsetse species Glossina morsitans morsitans (Gmm), we report on the draft genome sequence of its associated cytoplasmic Wolbachia endosymbiont
One interesting feature of Wolbachia genomes is the presence of high numbers of genes encoding proteins containing ankyrin repeat domains (ANK), which are thought to play an important role in host-symbiont interactions, the establishment of symbiosis and the induction of reproductive phenotypes [76]

Summary

Introduction

The genus Wolbachia encompasses intracellular maternally inherited Gram-negative bacteria estimated to infect over 40% of insect species, in addition to filarial nematodes, crustaceans, and arachnids [1,2]. Wolbachia interactions with its host can have diverse outcomes that range from mutualistic to pathogenic or reproductive parasitism [3]. Wolbachia alterations to host reproduction include parthenogenesis induction, male killing, feminization of genetic males, and cytoplasmic incompatibility (CI) [1,4]. In its simplest form, CI occurs when a Wolbachia infected male mates with an uninfected female, causing developmental arrest of the embryo. Wolbachia infected females can mate with either an uninfected male or a male infected with the same Wolbachia strain, and produce viable Wolbachia infected offspring. It has been suggested that the reproductive advantage afforded by the Wolbachia induced CI mechanism may permit the rapid spread of desirable host phenotypes into natural populations as a novel disease control approach [4,5,6,7]

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