Incipient evolution of Wolbachia compatibility types.
Cytoplasmic incompatibility (CI) is induced in arthropods by the maternally inherited bacterium Wolbachia. When infected males mate with uninfected females or with females bearing a different Wolbachia variant, paternal chromosomes behave abnormally and embryos die. This pattern can be interpreted as resulting from two bacterial effects: One (usually termed mod, for modification) would affect sperm and induce embryo death, unless Wolbachia is also present in the egg, which implies the existence of a second effect, usually termed resc, for rescue. The fact that CI can occur in crosses between males and females infected by different Wolbachia shows that mod and resc interact in a specific manner. In other words, different compatibility types, or mod/resc pairs seem to have diverged from one (or a few) common ancestor(s). We are interested in the process allowing the evolution of mod/resc pairs. Here this question is addressed experimentally after cytoplasmic injection into a single host species (Drosophila simulans) by investigating compatibility relationships between closely related Wolbachia variants naturally evolving in different dipteran hosts: D. simulans, Drosophila melanogaster, and Rhagoletis cerasi. Our results suggest that closely related bacteria can be totally or partially incompatible. The compatibility relationships observed can be explained using a formal description of the mod and resc functions, implying both qualitative and quantitative variations.
Charlat
Sylvain
S
Institut Jacques Monod, CNRS-Université Paris 6, Laboratoire Dynamique du Genome et Evolution, 2 place Jussieu, 75251 Paris 05, France. s.charlat@ucl.ac.uk
Riegler
Markus
M
Baures
Isabelle
I
Poinsot
Denis
D
Stauffer
Christian
C
Merçot
Hervé
H
D000818:Animals; D005075:Biological Evolution; D003433:Crosses, Genetic; D003593:Cytoplasm / Q000382:microbiology / Q000502:physiology; D004330:Drosophila / Q000382:microbiology* / Q000502:physiology; D006790:Host-Parasite Interactions; D008954:Models, Biological; D012098:Reproduction / Q000235:genetics / Q000502:physiology; D013045:Species Specificity; D018709:Statistics, Nonparametric; D033621:Tephritidae / Q000382:microbiology* / Q000502:physiology; D020577:Wolbachia / Q000235:genetics* / Q000502:physiology