Archaeal ancestors of eukaryotes: not so elusive any more
Eugene V. Koonin
Correspondence: Eugene V Koonin koonin@ncbi.nlm.nih.gov
BMC Biology 2015, 13:84 doi:10.1186/s12915-015-0194-5
Published: 5 October 2015
Abstract
The origin of eukaryotes is one of the hardest problems in evolutionary biology and sometimes raises the ominous specter of irreducible complexity. Reconstruction of the gene repertoire of the last eukaryotic common ancestor (LECA) has revealed a highly complex organism with a variety of advanced features but no detectable evolutionary intermediates to explain their origin. Recently, however, genome analysis of diverse archaea led to the discovery of apparent ancestral versions of several signature eukaryotic systems, such as the actin cytoskeleton and the ubiquitin network, that are scattered among archaea. These findings inspired the hypothesis that the archaeal ancestor of eukaryotes was an unusually complex form with an elaborate intracellular organization. The latest striking discovery made by deep metagenomic sequencing vindicates this hypothesis by showing that in phylogenetic trees eukaryotes fall within a newly identified archaeal group, the Lokiarchaeota, which combine several eukaryotic signatures previously identified in different archaea. The discovery of complex archaea that are the closest living relatives of eukaryotes is most compatible with the symbiogenetic scenario for eukaryogenesis.
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NOTA DESTE BLOGGER:
Uai, mas a tese de complexidade irredutível de Behe já não tinha sido refutada? Pelo menos é que diz a Galera dos meninos e meninas de Darwin e alguns cientistas na Nomenklatura científica. Mas Koonin, um dos gigantes em Biologia evolucionária dos séculos 20 e 21, parece que não se convenceu das refutações apresentadas, para mim foram todas tentativas pífias, e se deu ao trabalho árduo de refutar a tese da complexidade de Behe lá na raiz do LECA (last eukaryotic common ancestor - último ancestral comum eucariótico)! E nos apresentou apenas uma CENÁRIO???
Pano rápido! Fui, cada vez mais confiante na robustez da tese de complexidade irredutível - um FENÔMENO REAL detectado na natureza!
