Welcome to Journal of Tea Science,Today is

Journal of Tea Science ›› 2026, Vol. 46 ›› Issue (2): 221-237.doi: 10.13305/j.cnki.jts.2026.02.005

• Research Paper • Previous Articles     Next Articles

Analysis of Mitochondrial Genome Characteristics and Codon Usage Bias in Camellia sinensis cv. ‘Zhuyeqi’

CHEN Zhiyin1,2,3,4, ZENG Wenjuan1,2,3, YANG Pan1,2,3, WEN Cong1,2,3, JIANG Rui1,2,3, ZHONG Qianyi1,2,3, JING Yuanrong1,5, ZHU Zanjiang1,5,*   

  1. 1. College of Agriculture and Biotechnology, Hunan University of Humanities, Science and Technology, Loudi 417000, China;
    2. Innovation and Entrepreneurship Education Center for Horticultural Production and Processing in Hunan Province, Hunan University of Humanities, Science and Technology, Loudi 417000, China;
    3. Hunan University of Humanities, Science and Technology, Hunan Provincial Innovation and Entrepreneurship Demonstration Base, Loudi 417000, China;
    4. Key Laboratory of Characteristic Agricultural Resource Development and Quality Safety Control in Hunan Province, Hunan University of Humanities, Science and Technology, Loudi 417000, China;
    5. Loudi Crop Germplasm Resources Conservation and Utilization Engineering Technology Research Center, Loudi 417000, China
  • Received:2025-12-19 Revised:2026-02-17 Online:2026-04-15 Published:2026-04-22

Abstract: This study utilized Camellia sinensis cv. ‘Zhuyeqi’ as the research material and employed a combined strategy of Illumina ( the second-generation sequencing) and Oxford Nanopore (the third-generation sequencing) to systematically analyze and achieve a high-quality assembly of its mitochondrial genome. Furthermore, through gene annotation, codon usage bias analysis and phylogenetic analysis, this study aimed to elucidate the genetic mechanisms and evolutionary characteristics of Camellia sinensis cv. ‘Zhuyeqi’. The results indicate that the mitochondrial genome consists of seven fragments, including “one circular and six linear” structures, with a total length of 911 255 bp and a guanine-cytosine (GC) content of 45.7%. Among these fragments, fragment 1 is circular (311 104 bp), while the remaining fragments are linear. A total of 77 functional genes were annotated, including 38 protein-coding genes (PCGs), 33 transfer RNA (tRNA) genes, 3 ribosomal RNA (rRNA) genes, and 3 pseudogenes. Additionally, 269 simple sequence repeats (SSRs) were identified, with tetranucleotide repeats being the most abundant type (43.49%). Mononucleotide repeats were primarily composed of adenine (A)/thymine (T) (91.18%). A total of 780 long repeat sequences were identified, comprising 354 forward repeats and 426 palindromic repeats. The analysis of nonsynonymous substitutions (Ka) and synonymous substitutions (Ks) indicates that the ccmBrps10 and mttB genes are under significant and positive selection (Ka/Ks>1), suggesting their crucial roles in adaptive evolution to environmental conditions. Codon usage bias analysis reveals that the GC content of the third codon position (GC3, 37.36%) in 29 PCGs was significantly lower than that of the first (GC1, 47.81%) and second (GC2, 43.01%) codon positions. The mean effective number of codons (ENC) is 51.98, indicating weak codon usage bias. Regression analysis of GC12 and GC3 (R2 = 0.004 5) reveals that natural selection contributed 88.45%, significantly outweighing mutational pressure. Base preference shows C3>G3 and T3>A3, with optimal codons predominantly ending in uracil (U)/adenine (A) (60.87%). Phylogenetic analysis indicates that C. sinensis cv. ‘Zhuyeqi’ forms a monophyletic group with core species of the genus Camellia, supporting its taxonomic status. This study provided critical insights into the evolutionary mechanisms of the mitochondrial genome and the adaptive functions of genes in tea plants.

Key words: tea plant, C. sinensis cv. ‘Zhuyeqi’, mitochondrial genome, codon usage bias, phylogeny

CLC Number: