Cytoplasmic Incompatibility in Ticks – CYTOTICKS

In the CYTOTICKS project, we aim to test the hypothesis that the reproductive biology and evolution of ticks are manipulated by two of their native bacterial symbionts, Rickettsia and Rickettsiella, through the induction of cytoplasmic incompatibility (CI). Ticks are widely recognized for their ability to transmit pathogens, acting as a major vector of diseases and posing substantial risks to both human and veterinary health. However, our recent publications show that microbial communities hosted by ticks are predominantly composed of maternally inherited bacteria that do not infect vertebrates. Notably, our preliminary findings reveal that the genomes of certain tick-borne Rickettsia (Rickettsiales) and Rickettsiella (Legionellales) strains have lost the integrity of their virulence genes, yet have acquired the cif gene system, which is known to induce CI expression in a symbiont commonly found in insects, Wolbachia. Additionally, we have further confirmed that some Rickettsia and Rickettsiella strains extensively colonize ovaries of ticks, exhibit high-fidelity maternal transmission, and reach high prevalence within tick populations, a pattern expected for bacteria inducing CI. To date, we have identified more than 15 tick species harboring Rickettsia or Rickettsiella strains that carry the cif genes. In this context, our objectives are as follows:
(1) To experimentally test the expression of CI induced by Rickettsia and Rickettsiella in ticks.
(2) To validate the functionality of Rickettsia and Rickettsiella cif genes as reproductive manipulators.
(3) To characterize the impacts of CI on tick population genetics.
The CYTOTICKS project aims to explore novel aspects of tick biology, going far beyond the traditional focus on tick-borne diseases. The project's innovation lies in its ability to characterize new symbiotic effects on ticks, as well as their impact on tick evolution and biodiversity.