Coordinator: Didier Bouchon
Bacterial symbioses constitute a major evolutionary force. In this respect, vertically-transmitted intracytoplasmic symbionts represent models of choice. This is because their obligatory intracellular life style makes possible exchanges with hosts and induces important genetic changes in symbionts (e.g. genome size reduction, loss of mobile elements, etc.).
Wolbachia symbiosis presents exceptional features making it a unique and pertinent model for the analysis of eukaryotes-bacteria interactions: Wolbachia are vertically-transmitted, intracytoplasmic α-Proteobacteria found in 20-70% of arthropod species. This ancient symbiosis (>70 million years) is among the most frequent in the animal kingdom. Interactions between Wolbachia and its hosts vary from parasitism to obligatory mutualism which, in all cases, involve host reproduction manipulation (i.e. via cytoplasmic incompatibility, feminization, male-killing, parthenogenesis and requirement for oogenesis). The occurrence of numerous interspecific transfers of Wolbachia among hosts has been demonstrated and allows for transient or stable multi-infections that may promote genetic exchanges.
The goals of our research on Wolbachia are to understand the links existing between these different features and to analyze the evolutionary success of symbiosis. Can the demographic success of Wolbachia be explained by an important genomic plasticity conferring a high adaptation potential, associated to the mechanisms by which they manipulate host reproduction? We aim at identifying the mechanisms enabling the different types of associations between Wolbachia and their hosts, and the constraints resulting from the interactions. Strong aspects in our program include the sequencing of the Wolbachia genome harbored by the isopod Armadillidium vulgare, comparative genomic analyses, study of the role of mobile genetic elements, identification of factors of bacterial virulence and host resistance.
The results of our work will constitute bases for a better understanding of symbiosis, and will also allow to offer new strategies of control based on the manipulation of symbiotic populations, including the control or manipulation of vector arthropod populations and/or pathogenic agents.