Abstract: In order to understand the phylogenetic, codon bias and molecular evolution characteristics of DXS gene, the DXS gene sequences from 44 representative species were selected for analysis. The results showed that the DXS gene family was highly conserved and the mean genetic distance between sequences was 0.243. The differentiation time of DXS gene preceded the species differentiation, and the phylogenetic tree of DXS gene and species was the same topological structure. The gymnosperm, monocotyledonts and the same family plants of dicotyledonts were clustered together, respectively. The codon bias of DXS gene was low, and the average effective number of codon, GC3 and G+C contents were 47.25, 0.49 and 0.51, respectively. DXS gene was mainly subjected to purification selection in the evolutionary process, the DXS gene of Glycine soja with the maximum dN/dS of 0.981, and the DXS gene of Panicum hallii with the minimum dN/dS of 0.001, the average dN/dS was 0.094. There were no positive selection sites with BEB greater than 0.95 detected in all models. There was no significant correlation between the effective number of codon, GC3, G+C contents and the dN/dS of DXS gene. This study provided a theoretical basis for further research on the function of DXS gene and its regulatory mechanism in the MEP pathway.

Key words: DXS gene, phylogenetic analysis, codon bias, molecular evolution