The archaeal ‘TACK’ superphylum and the origin of eukaryotes

Although most hypotheses to explain the emergence of the eukaryotic lineage are conflicting, some consensus exists concerning the requirement of a genomic fusion between archaeal and bacterial components. Recent phylogenomic studies have provided support for eocyte-like scenarios in which the alleged ‘archaeal parent’ of the eukaryotic cell emerged from the Crenarchaeota/Thaumarchaeota. Here, we provide evidence for a scenario in which this archaeal parent emerged from within the ‘TACK’ superphylum that comprises the Thaumarchaeota, Crenarchaeota and Korarchaeota, as well as the recently proposed phylum ‘Aigarchaeota’. In support of this view, functional and comparative genomics studies have unearthed an increasing number of features that are uniquely shared by the TACK superphylum and eukaryotes, including proteins involved in cytokinesis, membrane remodeling, cell shape determination and protein recycling.