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Curr Biol. 2014 Feb 17;24(4):465-70. doi: 10.1016/j.cub.2014.01.036. Epub 2014 Feb 6.

An alternative root for the eukaryote tree of life.

Author information

1
Program in Systematic Biology, Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 75236 Uppsala, Sweden.
2
Program in Systematic Biology, Department of Organismal Biology, Uppsala University, Norbyvägen 18D, 75236 Uppsala, Sweden. Electronic address: sandra.baldauf@ebc.uu.se.

Abstract

The root of the eukaryote tree of life defines some of the most fundamental relationships among species. It is also critical for defining the last eukaryote common ancestor (LECA), the shared heritage of all extant species. The unikont-bikont root has been the reigning paradigm for eukaryotes for more than 10 years but is becoming increasingly controversial. We developed a carefully vetted data set, consisting of 37 nuclear-encoded proteins of close bacterial ancestry (euBacs) and their closest bacterial relatives, augmented by deep sequencing of the Acrasis kona (Heterolobosea, Discoba) transcriptome. Phylogenetic analysis of these data produces a highly robust, fully resolved global phylogeny of eukaryotes. The tree sorts all examined eukaryotes into three megagroups and identifies the Discoba, and potentially its parent taxon Excavata, as the sister group to the bulk of known eukaryote diversity, the proposed Neozoa (Amorphea + Stramenopila+Alveolata+Rhizaria+Plantae [SARP]). All major alternative hypotheses are rejected with as little as ∼50% of the data, and this resolution is unaffected by the presence of fast-evolving alignment positions or distant outgroup sequences. This "neozoan-excavate" root revises hypotheses of early eukaryote evolution and highlights the importance of the poorly studied Discoba for understanding the evolution of eukaryotic diversity and basic cellular processes.

PMID:
24508168
DOI:
10.1016/j.cub.2014.01.036
[Indexed for MEDLINE]
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