Influence du volume cellulaire sur les stratégies evolutives des cellules eucaryotes

Cell volume is a fundamental characteristic of living cells. In eukaryotes, cell size is a highly controlled phenotypic trait that modulates intracellular biochemistry, delineates the interaction of cells with their environment, and plays a role in the size of multicellular organisms. Cell volume is intimately linked to cell proliferation, and several processes have been identified that couple cell size and cell cycle progression, ensuring volume homeostasis at the population level. Surprisingly, despite the conservation of the core mechanisms underlying the division cycle, cell size can vary by several orders of magnitude between species. Thus, cell volume may be the product of evolutionary constraints while directly contributing to the adaptation strategies of eukaryotic cells. During my PhD, I therefore investigated whether the initial volume of a cell plays a role in its evolutionary trajectory in challenging environments. To this end, I used a unique fission yeast model that allowed me to generate distinct populations of genetically identical cells but with different average cell volumes. Using hyperosmotic stress as a model selective pressure, I combined this approach with experimental evolution methods to determine the influence of cell size on the evolution of these distinct populations. Remarkably, my studies revealed a striking interplay between cell volume and adaptation at the phenotypic, genetic, and mechanistic levels. Altogether, my results demonstrate that cell size can be a key adaptive driver, with implications for the evolutionary trajectories of eukaryotic cells exposed to deleterious environments.