Supplemental Material for Shropshire, Rosenberg, and Bordenstein, 2020

Wolbachia endosymbionts in arthropods often cause cytoplasmic incompatibility (CI) that results in embryonic death when infected males mate with uninfected females or females harboring different Wolbachia strains. Here, we use Drosophila transgenics and a variety of CI gene (cifA and cifB) homologs to test if sequence variation causes phenotypic variation in the strength of CI and incompatibilities between strains. We report that cif homologs cause weak and rescuable CI, closely related cifA homologs are often interchangeable and compatible, cifB sequence variation associates with CI levels, and divergent homologs can exhibit unidirectional CI against each other.