Codon usage and codon pair patterns in non-grass monocot genomes.

Area of Science:

• Genomics
• Molecular Evolution
• Bioinformatics

Background:

• Previous studies on monocot codon usage primarily focused on grasses, leading to generalizations for all monocots.
• This study investigates codon usage patterns in non-grass monocots to identify taxon-specific differences.

Purpose of the Study:

• To analyze codon usage, codon-pair context bias, and nucleotide composition in non-grass monocots.
• To compare these patterns with those observed in grasses and identify the evolutionary forces shaping them.

Main Methods:

• Reviewed existing literature on monocot codon usage.
• Analyzed four non-grass monocot genomes (Musa acuminata, Musa balbisiana, Phoenix dactylifera, Spirodela polyrhiza) with available transcriptome data.
• Measured relative synonymous codon usage, effective number of codons, derived optimal codon, and GC content.

Main Results:

• Identified optimal codons, rare codons, and preferred codon-pair contexts in non-grass monocots.
• Observed a unimodal distribution of GC3 content, contrasting with the bimodal distribution in grasses.
• Found a positive correlation between codon adaptation index (CAI) and GC3, and a negative correlation between GC3 and gene length, suggesting the impact of GC-biased gene conversion (gBGC).

Conclusions:

• Optimal codons in non-grass monocots favor G/C at the third codon position.
• GC-biased gene conversion (gBGC) is a primary driver of codon usage and nucleotide composition in non-grass monocots.