Bidirectional incompatibility among divergent Wolbachia and incompatibility level differences among closely related Wolbachia in Nasonia.
Most insect groups harbor obligate bacterial symbionts from the alpha-proteobacterial genus Wolbachia. These bacteria alter insect reproduction in ways that enhance their cytoplasmic transmission. One of the most common alterations is cytoplasmic incompatibility (CI) - a post-fertilization modification of the paternal genome that renders embryos inviable or unable to complete diploid development in crosses between infected males and uninfected females or infected females harboring a different strain. The parasitic wasp species complex Nasonia (N. vitripennis, N. longicornis and N. giraulti) harbor at least six different Wolbachia that cause CI. Each species have double infections with a representative from both the A and B Wolbachia subgroups. CI relationships of the A and B Wolbachia of N. longicornis with those of N. giraulti and N. vitripennis are investigated here. We demonstrate that all pairwise crosses between the divergent A strains are bidirectionally incompatible. We were unable to characterize incompatibility between the B Wolbachia, but we establish that the B strain of N. longicornis induces no or very weak CI in comparison to the closely related B strain in N. giraulti that expresses complete CI. Taken together with previous studies, we show that independent acquisition of divergent A Wolbachia has resulted in three mutually incompatible strains, whereas codivergence of B Wolbachia in N. longicornis and N. giraulti is associated with differences in CI level. Understanding the diversity and evolution of new incompatibility strains will contribute to a fuller understanding of Wolbachia invasion dynamics and Wolbachia-assisted speciation in certain groups of insects.
Bordenstein
S R
SR
Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, The Marine Biological Laboratory, Woods Hole, MA 02543, USA. sbordenstein@mbl.edu
Werren
J H
JH
D000818:Animals; D003433:Crosses, Genetic; D016680:Genome, Bacterial / Q000235:genetics; D049750:Genome, Insect / Q000235:genetics; D013045:Species Specificity; D013559:Symbiosis / Q000235:genetics*; D014863:Wasps / Q000235:genetics* / Q000382:microbiology*; D020577:Wolbachia / Q000235:genetics*