Gaurav’s large-scale phylogenetic analysis of bacterial tRNA modification systems is now published in MBE!
An important property of tRNA molecules is the ability for wobble base pairing. Apart from the widely known GU wobble pairing, chemically modified bases in a tRNA extend wobble base pairing rules. Such tRNA modifications therefore expand the pool of tRNA in the cell and allow a handful of tRNAs to recognize all 61 codons. tRNA modifications also reduce translational errors, increase bacterial growth, and improve virulence, and should therefore face strong positive selection. However, the evolutionary history of bacterial tRNA modifications and their impact on tRNA gene content has remained unclear.
In this paper, we mapped the occurrence of five known tRNA modifications across 1093 bacteria. We found that while most modifications were ancient, some were repeatedly lost in several major lineages. Interestingly, most losses of modifications were associated with the retention or secondary gain of unmodified tRNAs, which would complete the full tRNA set. And, subsequent gain or retention of unmodified tRNA was phylogenetically correlated with the genome GC content of bacteria. Thus, our paper highlights the complex interplay between GC content, tRNA genes and tRNA modifications, and traces their evolutionary history. We hope you enjoy reading the paper as much as we enjoyed working on this project!
Update: Also see an NCBS news piece about this work here.