A valine to leucine mutation in hypomorphic Wolbachia CidB reduces both deubiquitylation and cytoplasmic incompatibility

Abstract

Cytoplasmic incompatibility (CI) remains one of the most highly researched and applied phenotype conferred by the bacterium, Wolbachia on the host organisms it infects. For programs that rely on the CI phenomenon, the strength of CI expression is critical and must be maintained at high levels. Unfortunately, CI strength has been observed to vary and the determinants for the variability in cytoplasmic incompatibility (CI) strength remain unknown. While selection does not act to maintain CI strength, we show through a genomic and biochemical analysis that a valine to leucine mutation (V875L) in the deubiquitylating (DUB) domain of a Wolbachia CI-inducing gene reduces the cleavage capability and efficiency in cytoplasmic incompatibility deubiquitylating protein (CidB) responsible for causing CI. To describe this analysis, I focus on first re-introducing the CI phenomenon, its source, genetic factors, pathways, effects and real-world applications. Later, I talk about the discovery of hypomorphic (weak) CI and preliminary research done to narrow down probably determinants that might cause weak CI. Finally, I create a model to test the hypothesis that a certain valine to leucine mutation (V875L) in the DUB domain of the effector proteins of CI lead to varying strengths of CI commonly identified as hypormorphic CI in the wild.