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24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

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Charrier Pierre

Genomic diversity, evolution and adaptation in ticks Ixodes ricinus

Summary of the thesis :

Ticks are haematophagous acarians that are vectors of numerous micro-organisms, some of which are responsible for human or animal diseases (e.g. Lyme Borreliosis). The tick Ixodes ricinus, is widely distributed in Europe where it is the main vector of the agent responsible for Lyme disease. Three aspects were approached during this thesis, by carrying out high-throughput transcriptome sequencing for each point. In the first part, a catalogue of transcripts was reconstructed and annotated from individuals from different physiological conditions (developmental stages, gorgement state, sex). Differential expression analysis was used to determine which genes are expressed more specifically during gorgement (cuticular proteins in particular, but also metallo-proteases, etc.). In the second part, the genetic structure of I. ricinus was explored from twelve European populations. My results show for the first time a clear signal of geographical structuring and isolation by distance at the European scale. In the third part, I used a phylogenomic approach on the group of hard ticks: to do this, I reconstructed the transcriptomes of 27 tick species (including nine species sequenced for this project), making it possible to propose a very robust phylogenetic tree for this group.

Mots-clefs :

Transcriptome, Ixodes Ricinus, RNA-seq, Differential Expression Analysis, Population Genomics, Phylogenomics