Asaf Sajjad, Williams Yetunde A, Riethoven Jean-Jack M, Eslamieh Jason, Al-Rawahi Ahmed, Al-Harrasi Ahmed, Khan Abdul Latif
Natural and Medical Sciences Research Center, University of Nizwa, Nizwa, Sultanate of Oman.
Department of Engineering Technology, Cullen College of Engineering, University of Houston, Houston, TX, USA.
Funct Integr Genomics. 2025 Aug 25;25(1):172. doi: 10.1007/s10142-025-01682-2.
The genus Boswellia is famous for its commercially important frankincense production. Additionally, it has unique ecological and taxonomic importance. However, the Boswellia species often face natural hybridization, and the lack of genomic datasets frequently contributes to taxonomic uncertainties. Here, we sequenced and analyzed the complete plastid genomes (plastomes) of six Boswellia species (B. carteri, B. bullata, B. dioscoridis, B. elongata, B. serrata, B. frereana, and a hybrid variant of B. sacra (B. sacra var. supersacra). The genome size of Boswellia plastomes is between 159,189 bp and 160,743 bp, displaying a typical structure with large single-copy (LSC; 86,811-88,054), small single-copy (SSC; 26,666-26,763), and inverted repeat (IR; 26,544-26,763) regions. The IR regions (~ 25,000 bp) are highly conserved across species, contributing to the stability of the plastome structure. Our study identified consistent gene content, typical of angiosperms, and showed that the IR boundaries remained unchanged across species. The simple sequence repeats revealed a range between 43 and 52 across the plastomes, with B. sacra exhibiting the highest count. We detected long, repetitive sequences that could serve as useful genetic markers for species differentiation. Nucleotide diversity analysis highlighted significant gene variations (matK, rbcL, rpl14, and rpoC2). The results showed substantial genetic divergence in regions (rpl14, matK, and rpoC2), demonstrating distinct variations among species. In evolutionary history, the B. carteri diverged around 4.2 million years ago (mya), while B. sacra and B. serrata separated by approximately 7.0 mya. The phylogenomic analysis supported the distinction between B. carteri and B. sacra, challenging prior claims that these are synonymous. These findings contribute to a deeper understanding of species boundaries within Boswellia and offer valuable resources for future DNA barcoding efforts.
乳香属以其具有重要商业价值的乳香生产而闻名。此外，它还具有独特的生态和分类学重要性。然而，乳香属物种经常面临自然杂交，并且缺乏基因组数据集常常导致分类学上的不确定性。在此，我们对六种乳香属物种（卡氏乳香、泡状乳香、迪氏乳香、长叶乳香、锯齿乳香、弗雷氏乳香以及一种神圣乳香的杂交变种（神圣乳香超神圣变种））的完整质体基因组（质体基因组）进行了测序和分析。乳香属质体基因组的大小在159,189碱基对至160,743碱基对之间，呈现出具有大单拷贝（LSC；86,811 - 88,054）、小单拷贝（SSC；26,666 - 26,763）和反向重复（IR；26,544 - 26,763）区域的典型结构。IR区域（约25,000碱基对）在物种间高度保守，有助于质体基因组结构的稳定性。我们的研究确定了与被子植物典型一致的基因内容，并表明IR边界在物种间保持不变。简单序列重复显示整个质体基因组的范围在43至52之间，神圣乳香的数量最多。我们检测到可作为物种分化有用遗传标记的长重复序列。核苷酸多样性分析突出了显著的基因变异（matK、rbcL、rpl14和rpoC2）。结果显示在区域（rpl14、matK和rpoC2）存在大量遗传分歧，表明物种间存在明显差异。在进化史上，卡氏乳香大约在420万年前分化，而神圣乳香和锯齿乳香大约在700万年前分开。系统发育基因组分析支持了卡氏乳香和神圣乳香之间的区别，对之前认为它们是同义词的说法提出了挑战。这些发现有助于更深入地理解乳香属内的物种界限，并为未来的DNA条形码研究提供有价值的资源。
