Data from: Asgard archaea illuminate the origin of eukaryotic cellular complexity

The origin and cellular complexity of eukaryotes represent a major enigma
in biology. Current data support scenarios in which an archaeal host cell
and an alphaproteobacterial (mitochondrial) endosymbiont merged together,
resulting in the first eukaryotic cell. The host cell is related to
Lokiarchaeota, an archaeal phylum with many eukaryotic features. The
emergence of the structural complexity that characterizes eukaryotic cells
remains unclear. Here we describe the ‘Asgard’ superphylum, a group of
uncultivated archaea that, as well as Lokiarchaeota, includes Thor-, Odin-
and Heimdallarchaeota. Asgard archaea affiliate with eukaryotes in
phylogenomic analyses, and their genomes are enriched for proteins
formerly considered specific to eukaryotes. Notably, thorarchaeal genomes
encode several homologues of eukaryotic membrane-trafficking machinery
components, including Sec23/24 and TRAPP domains. Furthermore, we identify
thorarchaeal proteins with similar features to eukaryotic coat proteins
involved in vesicle biogenesis. Our results expand the known repertoire of
‘eukaryote-specific’ proteins in Archaea, indicating that the archaeal
host cell already contained many key components that govern eukaryotic
cellular complexity.