Analysis of synonymous codon usage patterns in seven different citrus species

Area of Science:

• Genomics
• Evolutionary Biology
• Molecular Biology

Background:

• Codon usage bias (CUB) is a significant factor in gene expression and evolution.
• Understanding CUB patterns in important fruit trees like Citrus is crucial for evolutionary insights.

Purpose of the Study:

• To characterize CUB patterns across seven Citrus species.
• To investigate the evolutionary effects of CUB on selection and base composition.
• To determine the factors influencing codon usage variation in Citrus.

Main Methods:

• Analysis of large expressed sequence tag (EST) datasets.
• Identification of preferred codons.
• Correspondence analysis and effective number of codons (ENCs) plots.
• Multiple regression analysis to assess gene expression influence.

Main Results:

• A- and T-ending codons are predominant in Citrus species.
• 21 preferred codons for 18 amino acids were identified across all species.
• Gene expression consistently influences the frequency of optional codons (FOP).
• Positive selection was detected during Citrus evolution, suggesting it drives codon usage.

Conclusions:

• Codon usage in Citrus is a result of positive selection.
• Translational selection is the primary driver of CUB in Citrus, with mutational bias and gene length playing lesser roles.
• The strong, selection-mediated codon bias in Citrus may be linked to its status as a widely cultivated fruit tree.