Convergence and minimal mutation criteria for evaluating early events in tRNA evolution

Area of Science:

• Evolutionary biology
• Molecular biology
• Bioinformatics

Background:

• Homology testing is crucial for understanding sequence relationships.
• Phylogenetic methods can reconstruct ancestral sequences.
• Transfer RNA (tRNA) evolution provides insights into genetic code development.

Purpose of the Study:

• To test sequence homology using convergent ancestral sequences.
• To investigate the evolutionary origins of different tRNA families (phenylalanine, tyrosine, glycine).
• To explore the early stages of genetic code evolution.

Main Methods:

• Independent reconstruction of ancestral sequences from different phylogenetic branches.
• Application of the convergence criterion to assess sequence homology.
• Comparative analysis of eukaryotic and prokaryotic tRNA sequences.

Main Results:

• All phenylalanine tRNAs demonstrate homology to a common ancestor.
• Eukaryotic and prokaryotic tyrosine tRNAs may have independent evolutionary origins.
• All glycine tRNAs share a common ancestor, with divergence predating eukaryotic-prokaryotic split.
• Structural similarities in prokaryotic glycine and valine tRNAs suggest a shared, ancient ancestor.

Conclusions:

• The convergence of ancestral sequences is a valid test for homology.
• Glycine tRNA evolution supports incremental genetic code elaboration.
• Tyrosine tRNA origins may be a key divergence point between eukaryotes and prokaryotes.