Abstract: To understand the codon bias of LaAP2 in Lepidium apetalum, LaAP2 gene codon bias was analyzed by Codon W, and EMBOSS programs was used to analyze the codon usage bias of the Lepidium apetalum LaAP2 gene. Correlation analysis was conducted to compare the bias of the Lepidium apetalum LaAP2 gene in model organisms for which relatively mature genetic transformation systems are available. Neutral drawing, ENc plots and parity rule 2 polt were subsequently used for the exploration of possible factors that affect the formation of the bias. The results showed that the ENc, CAI, and GC content of LaAP2 were respectively 48-65, 0-214, and 42-69%, indicating that the codon bias level of LaAP2 in Lepidium apetalum was low and biased toward the synonymous codons with A or T. According to the RSCU value, 11 codons showed high-frequency. Comparison of the codon usage preference of homolongous genes with other crops suggested that there was a certain difference in codon usage preference among AP2 genes in different species. The RSCU cluster analysis showed that the preference of LaAP2 gene was the closest to that of brassicaceae burnett in dicotyledonous plants. The codon base composition and correlation analysis showed that the codon bias of the Lepidium apetalum LaAP2 gene had many factors such as mutation and selective pressure playing an important role in shaping codon usage bias. Based on the analysis of the frequency of codon usage across species, the prokaryote E. coli expression system was found to be the most suitable for use with the LaAP2 gene, and the model plant Arabidopsis was the most ideal genetic transformation receptor of the LaAP2 gene. This study provided important reference information for further studies on the heterologous sexpression and the function of the LaAP2 gene in Lepidium apetalum.

Key words: Lepidium apetalum Willd., LaAP2 gene, codon usage bias, cluster analysis