| Summary: | Apicomplexan are unicellular eukaryotic microorganisms that have evolved towards strict parasitic lifestyle. Some apicomplexan groups include species that cause serious pathologies such as malaria (Plasmodium ssp.), toxoplasmosis (Toxoplasma gondii) and cryptosporidiosis (Cryptosporidium spp.). While the genomes of these highly pathogenic agents are now well documented, this is not the case for other apicomplexan lineages such as gregarines, which are considered basal within the Apicomplexa, have low pathogenicity and above all are non-cultivable. Their molecular study currently represents a major bottleneck, whereas a precise knowledge of their genomes would be essential to better understand the evolutionary history of apicomplexan parasites and the diversity of their adaptive paths to parasitic lifestyle. During this thesis the genome caracterisation of 2 marine gregarines, Porospora gigantea, parasite of the European lobster Homarus gammarus and Diplauxis hatti, parasite of the Polychaeta marine worm Perinereis cultrifera; and 1 terrestrial gregarine, Gregarina acridiorum, parasite of the locust Locusta migratoria have been carried out. The discovery of two coexisting genomes matching the morphologically described species P. gigantea, along with another example involving G. acridiorum illustrates the magnitude of the upcoming taxonomic revisions, and the need to turn to molecular markers, likely on a genomic scale, to properly assess the diversity of gregarines. Furthermore, the first comparative genomics analyses including gregarines reveal their unsuspected genetic diversity across Apicomplexa. An apicomplexan scale analyses of the glideosome proteins was also performed. This model refers to a complex molecular structure at the origin of gliding, a signature movement of Apicomplexa that is essential for the manifestation of their pathogenicity. A detailed comparative analysis highlights its differential conservation at the apicomplexan scale, suggesting a diversity of adaptations to motility and host cell ...
|
|---|