Mesona chinensis Benth (MCB) is one of the main economic crops in tropical and subtropical areas. To understand the codon usage bias (CUB) in M. chinensis Benth, chloroplast genome is essential to study its genetic law, molecular phylogenetic relationships, and exogenous gene expression. Results showed that the GC content of 53 CDS sequences was 37.95%, and GC1, GC2, and GC3 content were 46.02%, 38.26%, and 29.85%, respectively. The general GC content order was GC1>GC2>GC3. Moreover, the majority of genes had an effective number of codon (ENC) value greater than 40, except ndhE, rps8, and rps18. Correlation analysis results revealed that the GC content was significantly correlated with GC1, GC2, GC3, and ENC. Neutrality plot analysis, ENC-plot analysis, and PR2-plot analysis presented that the CUB of M. chinensis Benth chloroplast genome was mainly affected by mutation and selection. In addition, GGG, GCA, and TCC were found to be the optimal codons. Furthermore, results of cluster analysis and evolutionary tree showed that M. chinensis Benth was closely related to Ocimum basilicum, indicating that there was a certain correlation between the CUB of the chloroplast gene and the genetic relationship of plant species. Overall, the study on the CUB of chloroplast genome laid a basis for genetic modification and phylogenetic research of M. chinensis Benth chloroplast genome.

凉草（ Mesona chinensis Benth，MCB）是热带、亚热带地区的主要经济作物之一。为了了解中华木樨的密码子使用偏倚（CUB），叶绿体基因组对于研究其遗传规律、分子系统发育关系和外源基因表达至关重要。结果显示，53条CDS序列的GC含量为37.95%，GC1、GC2、GC3含量分别为46.02%、38.26%、29.85%。一般GC含量顺序为GC1>GC2>GC3。此外，除了ndhE、rps8和rps18之外，大多数基因的有效密码子数 (ENC) 值大于 40 。相关分析结果显示GC含量与GC1、GC2、GC3、ENC显着相关。中性图分析、ENC图分析和PR2图分析表明，中华木本叶绿体基因组的CUB主要受突变和选择的影响。此外，GGG、GCA 和 TCC 被发现是最佳密码子。此外，聚类分析和进化树结果表明，M. chinensis Benth与罗勒(Ocimum basilicum)亲缘关系较近，表明叶绿体基因的CUB与植物物种的亲缘关系存在一定的相关性。总体而言，叶绿体基因组CUB的研究为中华木本叶绿体基因组的遗传修饰和系统发育研究奠定了基础。