From: Université Paris-Saclay

Will give a seminar entitled:

On the Origin and Early Evolution of Eukaryotes

The origin of the eukaryotic cell, eukaryogenesis, was a major evolutionary transition that led to the emergence of complex cells from simpler ancestors. This process was followed by a rapid and wide diversification of lineages. Most of them correspond to unicellular eukaryotes (or protists), but some of them independently evolved complex forms of multicellularity (e.g. animals, plants, fungi or kelp). Reconstructing the phylogenetic tree of eukaryotes is important to unravel the underlying evolution of traits and to infer the features of the last eukaryotic common ancestor. How did that ancestor evolved? Although the endosymbiotic origin of mitochondria and chloroplasts from, respectively, Alphaproteobacteria and Cyanobacteria was clearly established more than four decades ago, the origin of the host to those bacteria remained elusive. The discovery and characterization of Asgard archaea, which harbor many genes in common with eukaryotes and are their closest relatives in phylogenomic trees, support scenarios of symbiosis between archaea and bacteria at the origin of the eukaryotic cell. I will briefly review these recent discoveries and the associated conceptual shift on eukaryogenesis, evoking current models and open questions and challenges.

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