Figure 1.

Qualitative maps of the radiations of tRNAomes for various species based on interpretation of evolutionary trees (Figures S1–S8). A) Model for LUCA; B) Three Pyrococcus species; C) Pyrobaculum aerophilium str. IM2; D) Staphylothermus marinus F1; E) Aeropyrum pernix K1; F) Sulfolobus solfataricus P2 (archaea); and G) Thermus thermophilus HB27 (bacteria). We posit that tRNAs are added to the code in the approximate order cyan→orange→green→purple→red. Asterisks (Pyrococcus; Figure 1B) indicate two tRNAs that appear to be reassigned to encode distinct amino acids compared to LUCA and other archaea.