Allelic Variation at tRNA Genes in Three Nematode Species Indicates Mutation Load Despite Strong Purifying Selection.

Area of Science:

• Evolutionary Biology
• Molecular Genetics
• Genomics

Background:

• Cytosolic transfer RNAs (tRNAs) are nuclear-encoded and prone to high mutation rates.
• Previous research hypothesized tRNAs contribute significantly to mutational load in populations.
• A comprehensive understanding of tRNA repertoire variation across species is lacking.

Purpose of the Study:

• To characterize the allelic variation within nuclear-encoded tRNA genes in three nematode species.
• To investigate the evolutionary pressures acting on tRNA genes.
• To compare tRNA gene organization and variation with protein-coding regions.

Main Methods:

• Analysis of within-species allelic variation in nuclear-encoded tRNAs.
• Examination of historical transcription-associated mutagenesis signatures.
• Assessment of purifying selection acting on tRNA genes.
• Comparison of tRNA genomic organization and variation patterns with protein-coding regions.

Main Results:

• tRNA genes exhibit signatures of high historical mutation rates and purifying selection.
• Allelic variation includes frequent mismatches between the tRNA's anticodon and its recognized amino acid.
• tRNA gene organization and variation patterns differ significantly from protein-coding regions.
• Individual nematode genomes possess distinct tRNA gene complements with potential functional implications.

Conclusions:

• Variation in tRNA repertoires is shaped by unique micro-evolutionary processes.
• These findings provide a basis for connecting tRNA evolution to broader macro-evolutionary patterns.
• Understanding tRNA variation is crucial, given its links to human disease.