Phage WO Infection Patterns In Fig Wasps And Association With MtDNA Variation Of Host Insect

Wolbachia (Alphaproteobacteria) are maternally inherited, endosymbiotic bacterium found in arthropods and filarial nematodes, which infect a diverse range of arthropods, with the rate ranging from20to76%in nature and can manipulate the reproduction system of its host in many ways. Bacteriophages are the most abundant organisms in the biosphere and play important roles in bacterial genome evolution. The temperate phage WO was first detected in2000, and is deemed to one of the rare reported cases of bacteriophage infection in Wolbachia. The distribution of WO is more widespread than you think. Many Wolbachia strains are infected with WO, and PCR amplification of the minor capsid gene orj7showed that the phage occurs in the majority of the parasitic A and B Wolbachia supergroups. Most phage-infected Wolbachia strains harbor low numbers of phages, only1or2different phage types were found in85%Wolbachia strains.Insect hosts-Wolbachia-phage WO is an ideal model system for studying tripartite interactions among viruses, bacteria and eukaryotes. To understand the microbial systems and their exploitation, it is important to unravel the phylogenetic relationship between Wolbachia and WO. Many researchers have investigated the relationship between Wolbachia and WO, including the insect hosts of Drosphila simulans, Ephestia kuehniella, Nasonia vitripennis, Culex pipens, Gryllus pennsylvanicus and so on, finding there is no phylogenetic congruence between Wolbachia and WO, suggesting the lateral transfer of WO in Wolbachia is common.Previous surveys of phage WO are sampled from open and semi-open communities; however, the infection pattern of WO in enclosed community is unreported. To detect the infection pattern of WO in a closed community and learn the phylogenetic relationship between WO and Wolbachia, we selected fig wasps to study. Figs and fig wasps constitude a well-known system of mutualism. Figs are pollinated on their inflorescences by their obligate fig wasps. Previous surveys have proved that the incidence of Wolbachia in fig wasps is almost the highest infection rate, up to59%-67%, remarkably higher than other insects.In the present study, we investigated23fig wasps species from three figs to elucidate the phage infection pattern and the following main conclusions:(1) The infection of Wolbachia in fig wasps was high, the infection incidence was83%. The infection of WO in fig wasps was low, the infection incidence was83%. Most species in fig wasps harbored single WO type;(2) There are no phylogenetic congruence between WO and Wolbachia, WO and fig wasps;(3) Based on the or f7gene, we found that WO have "host specific";(4) There are high frequency horizontal transfer among Wolbachia and WO;(5) WO could influence fig wasps mitochondrial variations.The infection of Wolbachia was high and the Wolbachia strains were complicated. And the infection of WO was high and the WO type was single, arousing our great interest. In addition to or/7sequences in our survey, tree-based analyses were performed for other21species insects commonly found in previous studies. The result revealed that phage WO from fig wasps clustered alone, showing "host-specific". The finding by analysis is that the acommunity the fig wasps lived may be the main factor. The fig syconium formed a relatively closed world isolate from the outside, and fig wasps have limited contact or communications with the outside world.Based on phylogenetic analyses, the phylogenetic relationship between Wolbachia and its host, WO and Wolbachia, WO and fig wasps isn’t express agreement. It indicates that WO and Wolbachia are able to successfully transfer itself horizontally between different insects except vertical transfer. So putative horizontal transfer routes of wsp and orf7types infecting more than one fig wasps species are assumed according to the sequences in three closed syconium. We discuss the mode of horizontal transfer of WO and the effect of frequent horizontal transmission of Wolbachia on phage transfer.We screened the species that have three infection patterns:(1) uninfected Wolbachia and uninfected WO;(2) infected Wolbachia and uninfected WO;(3) infected Wolbachia and infected WO. All individuals were divided into two groups, according to their WO infection status, in their mtDNA tree, indicating that WO could influence host mitochondrial variations. And the individuals infected Wolbachia and uninfected Wolbachia were no different.