Wolbachia infections in Nasonia vitripennis: A host-endosymbiont interaction study

Alok Tiwary, Biological Sciences, Indian Institute of Science Education and Research, Mohali, Mohali, India and Rhitoban Raychoudhury, BIOLOGICAL SCIENCES, Indian Institute of Science and Education Research Mohali, Mohali, India

Background/Question/Methods:
Wolbachia is a maternally inherited endosymbiont which alters its host’s reproductive biology in order to increase the number of Wolbachia-infected females in the population. One of these alterations include sperm-egg incompatibility known as Cytoplasmic Incompatibility (CI). CI leads to a Wolbachia infected male produce viable offspring only with a female having the same Wolbachia type infection. Thus two different Wolbachia types are also incompatible with each other (show CI between them). Wolbachia induces CI in the parasitoid host Nasonia vitripennis (Hymenoptera: Pteromalidae). World-wide population of Nasonia vitripennis is infected with two Wolbachia infections, one each from the supergroups of A and B. In case of multiple infection in a single host, several unanswered questions remain. How these infections are being maintained over long evolutionary time scale even though the two supergroups show CI between each other? Wolbachia also competes with the host for nutritional benefits. Many theoretical studies suggest mutualism as the preferred means for the existence of endosymbionts. However, Wolbachia maintains a parasitic relationship with the host. So, how these single and multiple Wolbachia infections are being maintained in the host over long evolutionary time scale?
Results/Conclusions:
To address these questions, we have separated the two infections in Nasonia vitripennis and have generated single lines for Wolbachia supergroup A and supergroup B infections. We have studied the dynamics of these infections at different developmental stage of its host Nasonia vitripennis. The study demonstrates a "cost" incurred on both the sexes of the host Nasonia vitripennis for the maintenance of single and multiple Wolbachia infections. Many of the life history traits like Progeny family size, fecundity, longevity, male mating potential etc. are compromised in the case of infected strains.
Even though Wolbachia-induced CI has been an area of attraction in recent times, the genetics basis of CI remains poorly understood. Using Nasonia vitripennis as a model system, we are also trying to understand how Wolbachia alters its host reproductive behavior? We have identified the stage of Nasonia vitripennis male development where CI is introduced by Wolbachia. We intend to find out the genes playing a role in this alteration by doing stage specific transcriptome studies. Our study will lead to deeper insights into the biology of Wolbachia-host interaction.