Comparative analysis of codon usage patterns in chloroplast genomes of ten Epimedium species

Abstract

BackgroundThe Phenomenon of codon usage bias exists in the genomes of prokaryotes and eukaryotes. The codon usage pattern is affected by environmental factors, base mutation, gene flow and gene expression level, among which natural selection and mutation pressure are the main factors. The study of codon preference is an effective method to analyze the source of evolutionary driving forces in organisms. Epimedium species are perennial herbs with ornamental and medicinal value distributed worldwide. The chloroplast genome is self-replicating and maternally inherited which is usually used to study species evolution, gene expression and genetic transformation.ResultsThe results suggested that chloroplast genomes of Epimedium species preferred to use codons ending with A/U. 17 common high-frequency codons and 2–6 optimal codons were found in the chloroplast genomes of Epimedium species, respectively. According to the ENc-plot, PR2-plot and neutrality-plot, the formation of codon preference in Epimedium was affected by multiple factors, and natural selection was the dominant factor. By comparing the codon usage frequency with 4 common model organisms, it was found that Arabidopsis thaliana, Populus trichocarpa, and Saccharomyces cerevisiae were suitable exogenous expression receptors.ConclusionThe evolutionary driving force in the chloroplast genomes of 10 Epimedium species probably comes from mutation pressure. Our results provide an important theoretical basis for evolutionary analysis and transgenic research of chloroplast genes.