Rapid divergence of codon usage patterns within the rice genome.

Area of Science:

• Genomics
• Evolutionary Biology
• Molecular Biology

Background:

• Synonymous codon usage exhibits considerable variation across and within genomes.
• The drivers of this variation, whether translational selection or mutational bias, remain debated.

Purpose of the Study:

• To differentiate the roles of mutational bias and translational selection in shaping codon usage patterns.
• To investigate codon usage heterogeneity within and between plant genomes.

Main Methods:

• Intra-genomic and inter-genomic comparisons of synonymous codon usage.
• Analysis of nucleotide content, particularly GC content, in relation to codon usage.
• Correlation analysis between codon bias and gene length.

Main Results:

• Rice genes display extreme codon usage heterogeneity, strongly correlated with nucleotide content (GC content).
• Arabidopsis genes show minimal variation in codon usage and nucleotide content.
• Evidence suggests rapid GC content evolution in some rice genes drives codon usage differences.
• Codon bias is negatively correlated with gene length.

Conclusions:

• Mutational bias can lead to substantial evolutionary divergence in codon usage.
• Heterogeneity in rice codon usage is explained by a balance between mutational biases and negative selection proportional to coding sequence length.
• Variations in synonymous codon usage are not primarily driven by selection on translational efficiency.