Wolbachia injection from usual to naive host in Drosophila simulans (Diptera: Drosophilidae)

Abstract

Abstract. Wolbachiapipientis (Hertig) (Rickettsiaceae) is an endocellular bacterium infecting numerous species of arthropods. The bacterium is harboured by males and females but is only transmitted maternally because spermatocytes shed their Wolbachia during maturation. The presence of this endosymbiont can lead to feminisation of the host, parthenogenesis, male-killing or reproductive incompatibility called cytoplasmic incompatibility (Cl). Although Wolbachia transmission is exclusively maternal, phylogenetic evi dence indicates that very rare inter-species transmission events have taken place. Horizontal transmission is possible in the labora tory by transferring cytoplasm from infected to uninfected eggs. Using this technique, we have artificially infected lines of the fruit fly Drosophila simulans Sturtevant (Drosophilidae). Recipient lines came from two different D. simulans populations. One ("naive" host) is not infected in the wild. The other ("usual" host) is a population naturally carrying Wolbachia in the wild. In this second case, recipient flies used in the experiment came from a stock culture that had been cured off its infection beforehand by an antibi otic treatment. Infected D. simulans laboratory stocks were used as donors. We assessed the three following parameters: (i) trans infection success rate (ratio of infected over total female zygote having survived the injection), (ii) level of cytoplasmic incompatibility expressed by trans-infected males three generations post-trans-infection, and (iii) infection loss rate over time in trans-infected lines (percentage of lines having lost the infection after 20 to 40 generations). We observed that parameter (i) did not differ significantly whether the recipient line came from a "naive" or a "usual" host population. However, both (ii) and (iii) were sig nificantly higher in the "naive" trans-infected stock, which is in agreement with earlier theoretical considerations.

Dynamics of double and single Wolbachia infections in Drosophila simulans from New Caledonia

“…We observed intermediate incompatibility when males infected with wHa were crossed with uninfected females (54% ± 8). Poinsot and Merçot (2001) also report low incompatibility in wHa infected males from New Caledonia (57.7%). In contrast, previous reports revealed strong incompatibly caused by wHa infected males from Hawaii and Tahiti when crossed with uninfected females (greater than 95%, O'Neill and Karr, 1990;Merçot et al, 1995b;James and Ballard, 2000).…”

“…One characteristic property of Wolbachia in D. simulans is its incompatibility phenotype. Although strains may induce strong, weak, or intermediate incompatibility, these simple phenotypic definitions are confounded by differences in host genetic background, which can greatly affect the bacterial expression of incompatibility (Poinsot and Merçot, 2001). This plasticity of phenotypic expression makes us wary of using the level of incompatibility in the definition of a strain until both host genetic background and Wolbachia density are controlled.…”

Generation of a novel Wolbachia infection in Aedes albopictus (Asian tiger mosquito) via embryonic microinjection

“…The presence of superinfection in G 0 but not thereafter suggests that maternal transmission between G 0 and G 1 represents a bottleneck for transfected Wolbachia and may result from artificially low infection levels in microinjected embryos or somatic G 0 infections that are not maternally inherited. Super-infection segregation following microinjection transfection has also been reported in Drosophila (Poinsot and Mercot, 2001;Riegler et al, 2004). It is useful to note that subsequent to G 1 , maternal transmission loss was not observed.…”

Symbiosis And The Origin Of Species

“…Wolbachia-induced phenotypes are then characterized in this new genetic background. The most common effect described in these studies is a change in CI level and bacterial densities when the Wolbachia are in a foreign genetic background (Boyle et al, 1993;Bordenstein and Werren, 1998;McGraw et al, 2001;Poinsot and Merçot, 2001). Other Wolbachia-host genotypic interactions include rescue of a Drosophila lethal mutation (Karr, 2000) and a phenotypic switch from feminization to male killing when a Wolbachia strain is experimentally transferred from one Lepidopteran species to another (Fujii et al, 2001).…”