Loss of reproductive parasitism following transfer of male-killing Wolbachia to Drosophila melanogaster and Drosophila simulans

Abstract

Wolbachia manipulate insect host biology through a variety of means that result in increased production of infected females, enhancing its own transmission. A Wolbachia strain (wInn) naturally infecting Drosophila innubila induces male killing, while native strains of D. melanogaster and D. simulans usually induce cytoplasmic incompatibility (CI). In this study, we transferred wInn to D. melanogaster and D. simulans by embryonic microinjection, expecting conservation of the male-killing phenotype to the novel hosts, which are more suitable for genetic analysis. In contrast to our expectations, there was no effect on offspring sex ratio. Furthermore, no CI was observed in the transinfected flies. Overall, transinfected D. melanogaster lines displayed lower transmission rate and lower densities of Wolbachia than transinfected D. simulans lines, in which established infections were transmitted with near-perfect fidelity. In D. simulans, strain wInn had no effect on fecundity and egg-to-adult development. Surprisingly, one of the two transinfected lines tested showed increased longevity. We discuss our results in the context of host-symbiont co-evolution and the potential of symbionts to invade novel host species.

Figure 1

Representative ovaries and testes of adult transinfected D. melanogaster (a and b) and transinfected D. simulans (c and d), respectively. Wolbachia are stained green and nuclei red (propidium iodide). Representative D. innubila egg chamber (e), the red stain is propidium iodide (which stains host and Wolbachia DNA), and the green is phalloidin (which stains F actin). Scale bars are 100 μm.