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

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.

Near-membrane iminocoumarin-based low affinity fluorescent Ca(2+) indicators.

Two new potential near-membrane iminocoumarin-based fluorescent Ca(2+) indicators were synthesized and the spectral profiles of their free and Ca(2+) bound forms were studied. The probes incorporate in their BAPTA-related structures, the 3-(benzimidazolyl)iminocoumarin or the 3-(benzothiazolyl)iminocoumarin moiety, substituted at the imino nitrogen with an n-dodecyl lipophilic chain. The compounds are excited with visible light and have Ca(2+) dissociation constant values of 5.50 and 4.49 microM, respectively, the highest reported to date in the literature. Fluorescence spectra studies indicated a clear shift in their excitation wavelength maxima upon Ca(2+) binding along with changes in fluorescence intensity that enable the compounds to be used as ratiometric near-membrane, low Ca(2+) affinity probes.