Recombination landscapes and genome evolution in flowering plants

Soutenance de thèse de Thomas Brazier (Université de Rennes 1, ECOBIO, OSUR)

Recombination landscapes and genome evolution in flowering plants
Mardi 13 décembre 2022, 13h00
Observatoire des Sciences de l'Univers de Rennes (OSUR) - Campus de Beaulieu, Bâtiment 14B, Salle de conférence

The jury will be composed of: Reviewers \* Crhistine Mézard, DR CNRS, INRAE Versailles IJPB \* Adam Eyre-Walker, Professor, University of Sussex Examiners \* Anne-Marie Chèvre, DR INRAE, IGEPP, INRAE Le Rheu \* Carina Farah Mugal, CR CRNS, LBBE Université Lyon 1 \* Laurent Duret, DR CRNS, LBBE Université Lyon 1 Supervisor \* Sylvain Glémin, DR CNRS, ECOBIO Université de Rennes 1 Keywords: comparative genomics, crossover, genetic shuffling, linkage disequilibrium, meiosis. Abstract: Meiotic recombination is a universal feature of sexually reproducing species during which crossovers play a fundamental role for the proper segregation of chromosomes and reshuffling alleles among chromosomes. How much variation in recombination is expected within a genome and among different species remains a central question for understanding the genomic consequences of recombination. We characterised and compared patterns of recombination at a broad scale in a comparative context amongst a large set of flowering plant species. We found two main patterns (with a few exceptions) associated with chromosome length, chromosome structure and gene density. As chromosome size increases, crossovers are distributed towards the periphery which globally corresponds to the underlying gene distribution and affects how efficiently genes are shuffled at meiosis. At a fine scale, we detected 5’-3’ gradients of recombination within coding regions in several species presenting a diversity in genomic characteristics and covering a broad phylogenetic scale. Recombination gradients were mainly shaped by the location and intensity of recombination hotspots in 5’ and 3’ ends of genes and by gene structure itself. Both ends of the transcribed region experience more recombination than the middle of genes which implies more recombination in shorter genes. These results raise new questions on the evolution of recombination rates but also on the impact of recombination on the diversity of genomic patterns such as polymorphism and base composition across and among species.