The tick species Ixodes ricinus is the most represented in France and Europe. It can transmit many pathogens: viruses, parasites, bacteria (including that responsible for Lyme disease). Knowing its genome should provide clues to fight against this tick and better manage the risks of pathogen transmission. The TiBoDi team of UMR BIOEPAR coordinates the scientific community studying this genome and ensures the dissemination of the results.

DNA sequence analysis

The sequencing and assembly of the genome (obtained at the chromosomal level) was carried out by the Genoscope (Evry). Annotation and functional analyses of the genes of interest are in progress, in collaboration with several European laboratories. Other partners mainly in Rennes (IRISA, Genouest) will participate in bioinformatic analyses and in making genome data available. The study of the tick genome and its variability will make it possible to identify the genetic bases of certain traits, such as the ability to harbour and transmit certain pathogens. It may also reveal sequences that have evolved in interaction with hosts, their pathogens, or with the tick's own parasites or pathogens.

Analysis of transcribed sequences

In addition to knowledge of the genome, it is interesting to know how this genome is expressed, i.e. which sequences are transcribed into RNA and then translated into functional proteins. Researchers at UMR BIOEPAR have carried out high-speed sequencing of the transcribed sequences of Ixodes ricinus and have identified a very complete catalogue of more than 190,000 transcripts. They then highlighted genes that express themselves differently depending on physiological states, for example before or during the blood meal, and which may therefore play a role in this blood meal. A second study based on tick transcriptomes broadened the field of study, this time including 27 different tick species. For this study, nine new transcriptomes were sequenced and combined with published data from other groups and for other species. The analysis consisted in reconstructing a catalogue of genes coding for each tick species and then using the core of genes common between these species to carry out a study of the phylogeny of this group.

References:

Charrier, N. P., Couton, M., Voordouw, M. J., Rais, O., Durand-Hermouet, A.,  Hervet, C., Plantard, O.,  & Rispe, C. (2018). Whole body transcriptomes and new insights into the biology of the tick Ixodes ricinus. Parasites & Vectors, 11(1), 364. 

Charrier, N. P., Hermouet, A., Hervet, C., Agoulon, A., Barker, S. C.,  Heylen, D., Toty, C., McCoy, K. D., Plantard, O., & Rispe, C. (2019). A transcriptome-based phylogenetic study of hard ticks (Ixodidae). Scientific Reports 9:12923. 

BIOEPAR members involved in the project: 

• Claude Rispe
• Olivier Plantard
• Caroline Hervet

DNA sequence analysis