Presence of Extensive Wolbachia Symbiont Insertions Discovered in the Genome of Its Host Glossina morsitans morsitans

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.

Genome of Rhodnius prolixus , an insect vector of Chagas disease, reveals unique adaptations to hematophagy and parasite infection

“…These regions spanned 100-2,500 bp, which were smaller and more dispersed than those reported in Glossina morsitans (two segments of ∼500 Kb) (9). A previous transcriptome analysis showed that eight of these genes appear to be transcribed in the midgut (10).…”

“Wigglesworthia morsitans” Folate (Vitamin B 9 ) Biosynthesis Contributes to Tsetse Host Fitness

“…It is also worth noting that within the bedbug (Cimex lectularius), Wolbachia symbionts are localized to bacteriomes and are associated with nutritional mutualism (82), in stark contrast to the reproductive parasitism resulting from these infections in most other insects. Further, significant portions of the Wolbachia genome have been inserted into the G. morsitans chromosomal DNA (58,83). Future analyses should examine whether these horizontal transfer events are associated with metabolic activity and the extent of these transfers in other tsetse fly species.…”

Abbreviations and acronyms

“…LGT of fragments of the Wolbachia genome (total size approximately 1.2 Mb), ranging from 500 base pairs to more than 1 Mb, have been observed in many invertebrates, including beetles (Nikoh et al, 2008), grasshoppers (Funkhouser-Jones, 2015;Toribio-Fernández et al, 2017), wasps (Dunning-Hotopp et al, 2007), fruit flies (Dunning-Hotopp et al, 2007;Klasson et al, 2014;Choi, Bubnell and Aquadro, 2015;Morrow et al, 2015), tsetse flies (Brelsfoard et al, 2014;Nakao et al, 2016), butterflies and moths , kissing bugs (Mesquita et al, 2015), mosquitoes (Klasson et al, 2009;Hou et al, 2014), filarial nematodes (Fenn et al, 2006;Dunning-Hotopp et al, 2007;Keroack et al, 2016) and spiders (Baldo et al, 2008).…”