Reconstruction of gene content for a putative last universal common ancestor

by Christos Ouzounis (National Center for Research & Technology, Thessalonica)

Friday 22 Mar 2013, 15:15 → 16:30 Europe/Stockholm

Magnelísalen (Arrheniuslaboratoriet)

Ever since the first genome sequences were produced, there has been a quest for the definition of a common core of gene and protein families shared by all organisms. Yet, this set of common families has been shrinking with the inclusion of an ever-increasing number of species. The subsquently proposed notion of a pangenome relates to this matter, as a data-driven definition of a common core for a 'superspecies', not always taking into account the loss and horizontal gene transfer of families across clades. During the last decade, an arsenal of methods for automated large-scale analysis of genomes resulted in more accurate computations of gene content and facilitated the inference of ancestral states for a given phylogeny, also known as paleogenomes. We discuss the historical development and the semantics of LUCA's initials, exempify the reconstruction of LUCA's gene content with different methods - taking into account factors that shape gene content - and demonstrate that contemporary genomes support the notion that LUCA was a complex entity. We also explain our recent attempts to infer the metabolic complement of ancestral pathway modules, going beyond gene content. Potential applications of paleogenomes include novel insights into deep phylogeny, module discovery for synthetic biology and life detection for planetary exploration.