The history of accretion of tRNA and RNase P RNA substructures reveals the early evolutionary appearance of Archaea. (a) Rooted trees of tRNA arm substructures reveal the early appearance of the acceptor arm (Acc) followed by the anticodon arm (AC) in Archaea or the pseudouridine (TC) arm in both Bacteria and Eukarya (from [108]). The result confirms the sister group relationship of Bacteria and Eukarya. (b) Trees of molecular substructures of RNase P RNAs were reconstructed from characters describing the geometry of their structures (from [135]). Branches and corresponding substructures in a 3D atomic model are colored according to the age of each substructure (nd, node distance). Note the early loss of stem P8 in Archaea immediately after the evolutionary assembly of the universal functional core of the molecule.
