Speaker
Description
Chloroplasts, crucial organelles in autotrophic organisms, possess distinctive regulatory pathways to control molecular processes that respond dynamically to environmental cues. Protein synthesis in these organelles relies on transfer RNAs (tRNAs) encoded by the chloroplast genome, which undergo extensive post-transcriptional modifications. These modifications play critical roles in accurate mRNA decoding, structural stability of tRNAs, modulation of amino acid charging, and efficient ribosomal recognition. While the phenomenon is common across all genetic systems, the landscape of chloroplast tRNA modification is not well characterised.
In this study, we investigated the post-transcriptional modifications in chloroplast tRNAs of Arabidopsis thaliana using tRNA sequencing, liquid chromatography-mass spectrometry, and analysis of public data. Our results revealed similarities between chloroplast tRNAs and bacterial systems (e.g., Escherichia coli), such as modification patterns at the anticodon-adjacent position and the variable loop of tRNAs. Additionally, we identified structural features shared with eukaryotic systems that likely contribute to the proper folding and functionality of chloroplast tRNAs. Notably, our tRNA-seq analysis identified the presence of the recently discovered 2-aminovaleramididine modification at the wobble position of tRNA-IleCAU, which is crucial for differentiating isoleucine codons from methionine codons.
These findings suggest that the chloroplast translation machinery, through co-evolution with its eukaryotic host, has adopted features beyond those typically found in bacteria, reflecting a blend of ancestral and acquired characteristics. This dual adaptation likely enhances the efficiency and fidelity of chloroplast translation, providing insight into the evolutionary convergence of chloroplast and eukaryotic systems.