Contrasting Patterns of Virus Protection and Functional Incompatibility Genes in Two Conspecific Strains from .

infections can present different phenotypes in hosts, including different forms of reproductive manipulation and antiviral protection, which may influence infection dynamics within host populations. In populations of two distinct strains coexist, each manipulating host reproduction: strain PanCI causes cytoplasmic incompatibility (CI), whereas strain PanMK causes male killing (MK). CI occurs when a -infected male mates with a female not infected with a compatible type of , leading to nonviable offspring. PanMK can rescue PanCI-induced CI but is unable to induce CI. The antiviral protection phenotypes provided by the PanCI and PanMK infections were characterized; the strains showed differential protection phenotypes, whereby cricket paralysis virus (CrPV)-induced mortality was delayed in flies infected with PanMK but enhanced in flies infected with PanCI compared to their respective -cured counterparts. Homologs of the and genes involved in CI identified in PanMK and PanCI showed a high degree of conservation; however, the CifB protein in PanMK is truncated and is likely nonfunctional. The presence of a likely functional CifA in PanMK and PanMK's ability to rescue PanCI-induced CI are consistent with the recent confirmation of CifA's involvement in CI rescue, and the absence of a functional CifB protein further supports its involvement as a CI modification factor. Taken together, these findings indicate that PanCI and PanMK have different relationships with their hosts in terms of their protective and CI phenotypes. It is therefore likely that different factors influence the prevalence and dynamics of these coinfections in natural hosts. strains are common endosymbionts in insects, with multiple strains often coexisting in the same species. The coexistence of multiple strains is poorly understood but may rely on organisms having diverse phenotypic effects on their hosts. As is increasingly being developed as a tool to control disease transmission and suppress pest populations, it is important to understand the ways in which multiple strains persist in natural populations and how these might then be manipulated. We have therefore investigated viral protection and the molecular basis of cytoplasmic incompatibility in two coexisting strains with contrasting effects on host reproduction.