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Séminaire PHILBIO invité Paul Rainey
Notre invité sera Paul RAINEY (New Zealand Institute for Advanced Studies). Il interviendra sur le thème suivant : "Origins of multicellularity"
Résumé: The evolution of multicellular life from unicellular predecessors marks a Major Evolutionary Transition that has been central to the emergence of complex biological form. Cooperation is central to the process, however the means by which the earliest groups of cells maintained integrity in the face of destructive cheating types is unclear. One idea posits cheats as a primitive germ line in a life cycle that facilitates group reproduction. I will describe an experiment in which simple cooperating lineages of bacteria were propagated under a selective regime that rewarded collective-level fecundity. Collectives reproduced via life cycles that either embraced, or purged, cheating types. When embraced, the life cycle alternated between phenotypic states. Selection fostered inception of a developmental switch that underpinned the emergence of collectives whose fitness, during the course of evolution, became decoupled from the fitness of constituent cells. Such development and decoupling did not occur when groups reproduced via a cheat-purging regime. The findings capture key events in the evolution of Darwinian individuality during the transition from single cells to multicellularity — they also draw attention to life cycles and the role they play in establishing conditions for selection to operate over time scales longer than those defined by the doubling time of individual cells. If time permits, I will discuss recent work at ESPCI using droplet technologies to construct ecological conditions sufficient to promote Major Evolutionary Transitions of an egalitarian type, such as those that led to evolution of the eukaryotic cell.