紫花苜蓿叶绿体基因组密码子偏好性分析.

To character the codon usage patterns of chloroplast genome in alfalfa, forty-nine coding DNA sequences were analyzed using CodonW, CUSP, CHIPS and SPSS softwares. The results were as follows:(1)The average GC content at the 3rd codon position was 26.44% in the alfalfa chloroplast genome. The effective codon number(ENC)ranged from 40.6 to 51.41, indicating that codon bias was weak in the alfalfa chloroplast genome.(2)Thirty codons showed relative synonymous codon usage(RSCU)value greater than 1, including 29 codons ending with A and U, which suggested that the third codon position preferred A or U.(3)Neutrality analysis showed no significant correlation was observed between GC3 and GC12, suggesting natural selection mainly contributed to the codon usage bias. ENC-plot analysis showed that there were some genes with low ENC values lying below or near the expected curve, which indicated that mutation also affected the formation of codon usage bias. In addition, 17 codons were identified as optimal codons in alfalfa. We concluded that the codon usage bias of alfalfa is formed under effect of natural selection and mutational bias. This study will lay a good foundation for development of chloroplast genetic engineering and molecular breeding of alfalfa. [ABSTRACT FROM AUTHOR]