关键词: 苜蓿, 密码子偏好性, 最优密码子, 基因编辑, 自然选择

Abstract: The genes codon usage of species has a bias,which can avoid the wrong incorporation of amino acids. The bias of Medicago codon has not been reported. In order to reveal the codon bias characteristics of Medicago genome,we used software to analyze the codon composition of the coding region,the relative synonymous codon use frequency (RSCU),and other parameters of four Medicago species to explore the codon bias characteristics. At the same time,we used various methods to analyze the influencing factors causing the codon bias of Medicago,and calculated the optimal codon of Medicago. Finally,the evolutionary relationship of codon usage bias among species was studied by cluster analysis. The results showed that the codon bias of four Medicago species was relatively weak,of which ‘Zhongmu No.1’ was the weakest,and the third position of Medicago codon prefered A/T;The codon bias of four Medicago species was greatly affected by natural selection pressure,and most of the optimal codons ended in A/T. The bias of four Medicago species was similar and close to Nicatiana tabacum L.and Solanum lycopersicum L.. This study provides a theoretical basis for the application of Medicago codon optimization,especially through the optimization to improve the expression of Cas9 protein to promote gene editing.

Key words: Medicago, Codon usage bias, Optimal codon, Gene editing, Natural selection