Complete chloroplast genome sequence of Camellia sinensis: genome structure, adaptive evolution, and phylogenetic relationships

The chloroplast (cp) genome holds immense potential for a variety of applications including species identification, phylogenetic analysis, and evolutionary studies. In this study, we utilized Illumina NovaSeq 6000 to sequence the DNA of Camellia sinensis L. cultivar 'Zhuyeqi', followed by the assembly of its chloroplast genome using SPAdes v3.10.1, with subsequent analysis of its features and phylogenetic placement. The results showed that the cp genome of 'Zhuyeqi' was 157,072 bp, with a large single-copy region (LSC, 86,628 bp), a small single-copy region (SSC,18,282 bp), and two inverted repeat regions (IR, 26,081 bp). The total AT and GC contents of the cp genome of 'Zhuyeqi' were observed to be 62.21% and 37.29%, respectively. The cp genome encoded 135 unique genes, including 90 protein-coding genes (CDS), 37 tRNA genes, and 8 rRNA genes. Moreover, 31 codons and 247 simple sequence repeats (SSRs) were identified. The cp genomes of 'Zhuyeqi' were found to be relatively conserved, with conservation observed in the IR region, which showed no evidence of inversions or rearrangements. The five regions with the largest variations were identified, with four regions (rps12, rps19, rps16, and rpl33) located in the LSC region and one divergent region (trnI-GAU) in the IR region. Phylogenetic analysis revealed that Camellia sinensis (KJ996106.1) was closely related to 'Zhuyeqi', indicating a close phylogenetic relationship between these two species. These findings could provide important genetic information for further research into breeding of tea tree, phylogeny, and evolution of Camellia sinensis.