Effects of host interaction withWolbachiaon cytoplasmic incompatibility in the two-spotted spider miteTetranychus urticae

The endosymbiotic bacterium Wolbachia pipientis infects a wide range of arthropods and induces a variety of reproductive anomalies, including cytoplasmic incompatibility (CI). Three populations of the two-spotted spider mite, Tetranychus urticae, were investigated in the present study. Based on gene sequencing, they had different host genetic backgrounds but were infected with the same Wolbachia strain. We also examined the CI level relative to host background, male age, Wolbachia density, and Ankyrin (ANK) gene expression in T. urticae. The results of the present study suggest that: (1) CI differences between populations appear to be a result of host genetic background; (2) male age is not a factor determining intensity of CI; (3) Wolbachia density in males may serve as threshold factor necessary for the CI to occur in T. urticae, after which other factors become important in determining the strength of CI; and (4) hosts may modulate CI intensity through modulation of ANK gene expression in males. Our results describe a new type of interaction between Wolbachia and its hosts, and the effect of the interactions on CI. Further investigations on the functions of Wolbachia ankyrin gene products and their host targets, particularly with respect to host reproductive manipulation, are also imperative.