Xu Xue-Min, Liu Dan-Hui, Zhu Shi-Xin, Wang Zhen-Long, Wei Zhen, Liu Quan-Ru
School of Life Sciences, Zhengzhou University, Zhengzhou, 450001, China.
College of Life Sciences, Beijing Normal University, Beijing, 100875, China.
Plant Divers. 2023 Mar 15;45(4):409-421. doi: 10.1016/j.pld.2023.03.004. eCollection 2023 Jul.
The genus comprises nearly 60 species mainly distributed in East and Southeast Asia. China has the largest number of species in the world, with a total of 44 species, of which 38 are endemic. Nutlet morphology is useful for the taxonomic delimitation of . However, there are still controversial circumscriptions of nutlet shape in some species. In previous studies, interspecies phylogenetic relationships were inferred using few DNA markers and very few taxa, which possibly led to erroneous or incomplete conclusions. In this study, the nutlet morphology of 39 taxa and the characteristics of 34 complete chloroplast genomes (29 taxa) were investigated and analyzed. Then, the phylogenetic relationships were discussed within this genus based on complete chloroplast genomes. To the best of our knowledge, this study is the first comprehensive analysis of nutlet morphology and complete chloroplast genome of . Based on nutlet morphology, can be divided into two groups: Group 1, hemispherical or oblique tetrahedron with carpopodiums, and Group 2, inverted tetrahedron without carpopodiums The chloroplast genome of exhibited a typical quadripartite structure, including 84-86 protein-coding, 37 transfer RNA, and 8 ribosomal RNA genes, with a total length of 147,247-148,986 bp. Genes in the junctions were well conserved in , similar to those in other Boraginaceae s.str. species. Furthermore, chloroplast genomes showed relatively high diversity, with more conserved genic regions than intergenic regions; in addition, we detected 14 hot spots (Pi > 0.005) in non-coding regions. Phylogenetic analyses based on chloroplast genome data identified highly resolved relationships between species. Specifically, was divided into two clades with strong support: one clade included species with hemispherical or oblique tetrahedron nutlets with carpopodiums and bracts, whereas the other clade included species with inverted tetrahedron nutlets without carpopodiums or bracts. Our results may inform future taxonomic, phylogenetic, and evolutionary studies on Boraginaceae.
该属包含近60个物种，主要分布在东亚和东南亚。中国拥有世界上最多的物种，共有44种，其中38种为特有种。小坚果形态对于该属的分类界定很有用。然而，一些物种的小坚果形状界定仍存在争议。在先前的研究中，种间系统发育关系是通过很少的DNA标记和极少的分类群推断出来的，这可能导致错误或不完整的结论。在本研究中，对39个分类群的小坚果形态和34个完整叶绿体基因组（29个分类群）的特征进行了调查和分析。然后，基于完整的叶绿体基因组讨论了该属内的系统发育关系。据我们所知，本研究是对该属小坚果形态和完整叶绿体基因组的首次综合分析。基于小坚果形态，该属可分为两组：第一组，具果柄的半球形或斜四面体；第二组，无果柄的倒四面体。该属的叶绿体基因组呈现典型的四分体结构，包括84 - 86个蛋白质编码基因、37个转运RNA基因和8个核糖体RNA基因，全长147,247 - 148,986 bp。该属中连接区的基因保守性良好，与其他紫草科狭义物种相似。此外，该属的叶绿体基因组显示出相对较高的多样性，基因区域比基因间区域更保守；此外，我们在非编码区域检测到14个热点（Pi > 0.005）。基于叶绿体基因组数据的系统发育分析确定了该属物种之间高度解析的关系。具体而言，该属被强烈支持地分为两个分支：一个分支包括具果柄和苞片的半球形或斜四面体小坚果的物种，而另一个分支包括无果柄或苞片的倒四面体小坚果的物种。我们的结果可能为未来紫草科的分类、系统发育和进化研究提供参考。
