Jiang Dongzhen, Zhou Lei, Ran Zhaohui, Xiao Xu, Yang Xuehang, Li Zhi
College of Forestry, Guizhou University, Guiyang, China.
BMC Genomics. 2025 May 15;26(1):490. doi: 10.1186/s12864-025-11673-z.
Camellia tachangensis F. C. Zhang is an endemic Camellia species of the junction of Yunnan, Guizhou and Guangxi Provinces in China. It is characterized by a primitive five-chambered ovary morphology and serves as the botanical source of the renowned "Pu'an Red Tea". Unfortunately, the populations of the species have declined due to the destruction of their habitats by human activities. The lack of mitochondrial genomic resources has hindered research into molecular breeding and phylogenetic evolution of C. tachangensis.
In this study, we had sequenced, assembled, and annotated the mitochondrial genome of C. tachangensis to reveal its genetic characteristics and phylogenetic relation with other Camellia species. The assembly result indicated that the mitochondrial genome sequence of C. tachangensis was 746,931 bp (GC content = 45.86%). It consisted of one multibranched sequence (Chr1) and one circular sequence (Chr2), with Chr1 capable of producing 7 substructures. The comparative analysis of the mitochondrial and chloroplast DNA of C. tachangensis revealed 23 pairs of chloroplast homologous fragments, with 10 fully preserved tRNA genes within them. Interspecies comparison of Ka/Ks ratios revealed that mutations in mitochondrial protein-coding genes (PCGs) of C. tachangensis were predominantly shaped by purifying selection throughout its evolution (Ka/Ks < 1). The mitochondrial CDS-based phylogenetic tree indicated that within the Camellia lineage, C. tachangensis was phylogenetically independent of the species of sections Oleifera, Camellia, Heterogenea, and Chrysantha. However, it also did not support the clustering of C. tachangensis with certain variants of C. sinensis, due to the extremely low support (BS = 22, PP = 0.41). Meanwhile, the chloroplast PCG-based phylogenetic analysis revealed that C. tachangensis formed a strongly supported basal clade (BS = 100, PP = 1.00), alongside C. makuanica (NC_087766), C. taliensis (NC_022264), and C. gymnogyna (NC_039626).
Our study deciphered the mitochondrial genome and its multibranched structure of C. tachangensis. These findings not only enhanced our comprehension of the complexity and diversity of mitochondrial genome structures in Camellia species, but also established a foundational genetic data framework for future research on molecular breeding programs and phylogenetic relationship involving C. tachangensis and its related species.
大厂茶（Camellia tachangensis F. C. Zhang）是中国云南、贵州和广西三省交界处的一种特有山茶物种。其特征是具有原始的五心皮子房形态，是著名的“普安红茶”的植物来源。不幸的是，由于人类活动对其栖息地的破坏，该物种的种群数量已经下降。线粒体基因组资源的缺乏阻碍了对大厂茶分子育种和系统发育进化的研究。
在本研究中，我们对大厂茶的线粒体基因组进行了测序、组装和注释，以揭示其遗传特征以及与其他山茶物种的系统发育关系。组装结果表明，大厂茶的线粒体基因组序列为746,931 bp（GC含量=45.86%）。它由一个多分支序列（Chr1）和一个环状序列（Chr2）组成，Chr1能够产生7个子结构。大厂茶线粒体和叶绿体DNA的比较分析揭示了23对叶绿体同源片段，其中有10个完全保留的tRNA基因。种间Ka/Ks比值比较显示，大厂茶线粒体蛋白编码基因（PCG）的突变在其整个进化过程中主要受纯化选择的影响（Ka/Ks < 1）。基于线粒体CDS的系统发育树表明，在山茶谱系中，大厂茶在系统发育上独立于油茶组、山茶组、异形山茶组和金花茶组的物种。然而，由于支持率极低（BS = 22，PP = 0.41），它也不支持大厂茶与某些中华变种聚类。同时，基于叶绿体PCG的系统发育分析表明，大厂茶与马关茶（NC_087766）、大理茶（NC_022264）和秃房茶（NC_039626）一起形成了一个得到强烈支持的基部类群（BS = 100，PP = 1.00）。
我们的研究解析了大厂茶的线粒体基因组及其多分支结构。这些发现不仅增强了我们对山茶物种线粒体基因组结构复杂性和多样性的理解，也为未来涉及大厂茶及其相关物种的分子育种计划和系统发育关系研究建立了基础遗传数据框架。
