title: Quest for Ancestors of Eukaryal Cells Based on Phylogenetic Analyses of Aminoacyl-tRNA Synthetases.
abstract: The three-domain phylogenetic system of life has been challenged, particularly with regard to the position of Eukarya. The recent increase of known genome sequences has allowed phylogenetic analyses of all extant organisms using concatenated sequence alignment of universally conserved genes; these data supported the two-domain hypothesis, which place eukaryal species as ingroups of the Domain Archaea. However, the origin of Eukarya is complicated: the closest archaeal species to Eukarya differs in single-gene phylogenetic analyses depending on the genes. In this report, we performed molecular phylogenetic analyses of 23 aminoacyl-tRNA synthetases (ARS). Cytoplasmic ARSs in 12 trees showed a monophyletic Eukaryotic branch. One ARS originated from TACK superphylum. One ARS originated from Euryarchaeota and three originated from DPANN superphylum. Four ARSs originated from different bacterial species. The other 8 cytoplasmic ARSs were split into two or three groups in respective trees, which suggested that the cytoplasmic ARSs were replaced by secondary ARSs, and the original ARSs have been lost during evolution of Eukarya. In these trees, one original cytoplasmic ARS was derived from Euryarchaeota and three were derived from DPANN superphylum. Our results strongly support the two-domain hypothesis. We discovered that rampant-independent lateral gene transfers from several archaeal species of DPANN superphylum have contributed to the formation of Eukaryal cells. Based on our phylogenetic analyses, we proposed a model for the establishment of Eukarya.
authors.affiliation: Laboratory of Extremophiles, Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, Japan.
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Furukawa
authors.affiliation: Laboratory of Extremophiles, Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, Japan.
authors.forename: Mizuho
authors.initials: M
authors.lastname: Nakagawa
authors.affiliation: Laboratory of Extremophiles, Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Kuroyanagi
authors.affiliation: Laboratory of Extremophiles, Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Yokobori
authors.affiliation: Laboratory of Extremophiles, Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, Japan. yamagish@toyaku.ac.jp.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yamagishi
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics*; D001105:Archaea / Q000235:genetics; D001419:Bacteria / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D005075:Biological Evolution; D003198:Computer Simulation; D056890:Eukaryota / Q000235:genetics*; D005057:Eukaryotic Cells; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal / Q000235:genetics; D008957:Models, Genetic; D010802:Phylogeny; D016415:Sequence Alignment / Q000379:methods
chemical_list: D000604:Amino Acyl-tRNA Synthetases
keywords: Aminoacyl-tRNA synthetase; DPANN superphylum; Last eukaryal common ancestor (LECA); Phylogenetic analysis