华北落叶松叶绿体基因组特征及密码子偏好性分析OA

In order to promote the molecular breeding process of Larix principis-rupprechtii and provide a basis for the utilization and innovation of its germplasm resources,the chloroplast genome structure char-acteristics and codon use preference model were analyzed using needle samples as research materials.The results showed that:1)The chloroplast genome of Larix principis-rupprechtii was 122 588 bp in length,with a total GC content of 38.74%.There were no typical inverted repeat sequences.A total of 115 genes were encoded,including 77 protein-coding genes,34 transfer RNA genes,and 4 ribosomal RNA genes.2)The average GC content of all codons in the 43 CDS sequences of the chloroplast genome of Larix principis-rupprechtii was 40.17%.The GC content at different positions was ranked as GC1(49.60%)＞GC2(41.31%)＞GC3(30.06%).The average values of CAI,CBI,and Fop were 0.174,-0.075,and 0.368,respectively,and the average value of ENC was 49.31,indicating a low gene expression level and weak codon usage bias in the chloroplast genome.3)The analysis results of correlation,neutral plotting,ENC-plot,and PR2-plot revealed that the formation of codon bias in the chloroplast genes of Larix principis-rupprechtii was mainly influenced by natural selection,while the influences of mutation pressure,base composition,and expression efficiency were relatively small.4)A total of 13 optimal codons were screened out,12 of which ended with A and U.Compared with other conifer species,the chloroplast genome of Lar-ix principis-rupprechtii showed a consistent codon usage bias,but also showed a high stability.The opti-mal codons selected can be applied to the chloroplast gene engineering of Larch,so as to optimize the prim-ers design to enhance the translation and transcription efficiency and improve the expression level of exoge-nous genes.