Comparative analysis of codon usage patterns in chloroplast genomes of six species.

plants are important as suppliers of biodiesel. In the current study, the codon usage patterns and sources of variance in chloroplast genome sequences of six different plant species have been systematically analyzed. Our results revealed that the chloroplast genomes of six plant species were biased towards A/T bases and A/T-ending codons, followed by detection of 17 identical high-frequency codons including GCT, TGT, GAT, GAA, TTT, GGA, CAT, AAA, TTA, AAT, CCT, CAA, AGA, TCT, ACT, TAT and TAA. It was found that mutation pressure was a minor factor affecting the variation of codon usage, however, natural selection played a significant role. Comparative analysis of codon usage frequencies of six plant species with four model organisms reflected that , , and should be considered as suitable exogenous expression receptor systems for chloroplast genes of six plant species. Furthermore, it is optimal to choose as the exogenous expression receptor. The outcome of the present study might provide important reference information for further understanding the codon usage patterns of chloroplast genomes in other plant species.