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Acta Prataculturae Sinica ›› 2023, Vol. 32 ›› Issue (7): 85-95.DOI: 10.11686/cyxb2022332

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Codon usage bias analysis of the chloroplast genome of Bothriochloa ischaemum

Shou-yu GAO(), Yu-ying LI(), Zhi-qing YANG, Kuan-hu DONG(), Fang-shan XIA   

  1. College of Grassland Science,Shanxi Agricultural University,Jinzhong 030801,China
  • Received:2022-08-17 Revised:2022-11-04 Online:2023-07-20 Published:2023-05-26
  • Contact: Yu-ying LI,Kuan-hu DONG

Abstract:

The chloroplast genome is highly conserved and has a slow evolutionary rate. The study of chloroplast genome codon bias could clarify the expression efficiency of genes, and could even determine plant phylogeny and species evolution. In order to analyze the phylogenetic relationship between Bothriochloa ischaemum and its related species, we analyzed the codon usage pattern of the chloroplast genome of B. ischaemum using CAIcal and CodonW1.4.2 software, and a cluster map was constructed using relative synonymous codon usage (RSCU) of B. ischaemum and its related species. Results showed that the average guanine-cytosine (GC) content was 38.79% in the B. ischaemum chloroplast genome sequences which had been screened, and the content was GC1>GC2>GC3. In these sequences, the third base of the codon was mostly A or U. The number of effective codons (ENC) ranges from 36 to 61 and indicates that the codon bias of B. ischaemum is weak. In addition, a total of 26 codons are used with high frequency, among which 25 codons end in A or U. Combined with the analyses of neutral plot, ENC-plot, ENC ratio and PR2-plot, we found that the codon bias of chloroplast genes of B. ischaemum is affected by both mutation pressure and natural selection, and the effect of mutation pressure is greater. Through the RSCU data analysis, a total of 15 optimal codons were screened from B. ischaemum chloroplast genome, and all of these end in A or U. In the present study, RSCU clustering showed that the codon usage pattern of B. ischaemum is different from that of related species. The present study therefore provides a reference for phylogenetic study of plants of the genus Bothriochloa.

Key words: chloroplast genome, Bothriochloa ischaemum, codon usage bias, optimal codons