title: Asgard archaea illuminate the origin of eukaryotic cellular complexity.
abstract: 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.
authors.affiliation: Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Zaremba-Niedzwiedzka
authors.affiliation: Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
authors.forename: Eva F
authors.initials: EF
authors.lastname: Caceres
authors.affiliation: Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
authors.forename: Jimmy H
authors.initials: JH
authors.lastname: Saw
authors.affiliation: Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
authors.forename: Disa
authors.initials: D
authors.lastname: Bäckström
authors.affiliation: Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
authors.forename: Lina
authors.initials: L
authors.lastname: Juzokaite
authors.affiliation: Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
authors.forename: Emmelien
authors.initials: E
authors.lastname: Vancaester
authors.affiliation: Department of Marine Science, University of Texas-Austin, Marine Science Institute, Port Aransas, Texas 78373, USA.
authors.forename: Kiley W
authors.initials: KW
authors.lastname: Seitz
authors.affiliation: Department of Earth and Planetary Sciences, and Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA.
authors.forename: Karthik
authors.initials: K
authors.lastname: Anantharaman
authors.affiliation: Section for Microbiology and Center for Geomicrobiology, Department of Bioscience, Aarhus University, DK-8000 Aarhus, Denmark.
authors.forename: Piotr
authors.initials: P
authors.lastname: Starnawski
authors.affiliation: Section for Microbiology and Center for Geomicrobiology, Department of Bioscience, Aarhus University, DK-8000 Aarhus, Denmark.
authors.forename: Kasper U
authors.initials: KU
authors.lastname: Kjeldsen
authors.affiliation: GNS Science, Extremophile Research Group, Private Bag 2000, Taupō 3352, New Zealand.
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Stott
authors.affiliation: Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka 237-0061, Japan.
authors.forename: Takuro
authors.initials: T
authors.lastname: Nunoura
authors.affiliation: Department of Earth and Planetary Sciences, and Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA.
authors.forename: Jillian F
authors.initials: JF
authors.lastname: Banfield
authors.affiliation: Section for Microbiology and Center for Geomicrobiology, Department of Bioscience, Aarhus University, DK-8000 Aarhus, Denmark.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schramm
authors.affiliation: Department of Marine Science, University of Texas-Austin, Marine Science Institute, Port Aransas, Texas 78373, USA.
authors.forename: Brett J
authors.initials: BJ
authors.lastname: Baker
authors.affiliation: Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
authors.forename: Anja
authors.initials: A
authors.lastname: Spang
authors.affiliation: Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
authors.forename: Thijs J G
authors.initials: TJ
authors.lastname: Ettema
mesh_terms: D001105:Archaea / Q000145:classification / Q000166:cytology* / Q000235:genetics*; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics; D022181:COP-Coated Vesicles / Q000378:metabolism; D056890:Eukaryota / Q000145:classification / Q000166:cytology* / Q000235:genetics; D005057:Eukaryotic Cells / Q000145:classification / Q000166:cytology* / Q000378:metabolism; D019143:Evolution, Molecular; D020745:Genome, Archaeal / Q000235:genetics*; D056186:Metagenomics; D008954:Models, Biological; D010802:Phylogeny
chemical_list: D019843:Archaeal Proteins