Abstract

Tandemly arranged repetitive regions (repeats) that encode 5S rRNA (5S rDNA) are an indispensable component of eukaryotic genomes. Typically, 5S rDNA repeats within a genome are very similar due to the concerted nature of the evolution of this type of repeats. Each 5S rDNA repeat consists of an evolutionarily conserved coding sequence (CDS) and a variable intergenic spacer (IGS). 5S rDNA is a popular model for studying the molecular evolution of repetitive sequences, and the high rate of IGS mutations determines its wide use in phylogenetic analysis of closely related taxa. Nevertheless, 5S rDNA remains unexplored for many groups of higher plants, especially for the Plumbaginaceae family. Some taxa of this family are endemic to southern Ukraine and listed in the Red Book. However, their taxonomic status is controversial, and its clarification requires the use of molecular phylogenetic methods. In this work, we examined the molecular organization of 5S rDNA for representatives of four genera of the tribe Limonieae, the largest in the family Plumbaginaceae. It was shown that the CDS of 5S rDNA of representatives of the genera Limonium, Armeria, and Ceratolimon possess single mutations that do not affect the formation of the secondary structure of 5S rRNA. In contrast, in the genomes of Goniolimon species, in addition to functionally normal 5S rDNA repeats, numerous pseudogenes were found that do not evolve in a concerted manner and contain numerous mutations in the CDS that disrupt the secondary structure of 5S rRNA. A significant phylogenetic distance between representatives of the subgenera Pteroclados and Limonium of the genus Limonium indicates that Pteroclados can be considered a separate genus. The high rate of molecular evolution makes 5S rDNA IGS a convenient tool for the reconstruction of phylogenetic relationships within the studied genera of the tribe Limonieae and the barcoding of Ukrainian endemics of the genus Limonium.

中文翻译：

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白花丹科 5S 核糖体 DNA

摘要

编码 5S rRNA (5S rDNA) 的串联排列的重复区域（重复）是真核基因组不可或缺的组成部分。通常，基因组内的 5S rDNA 重复非常相似，因为此类重复的进化具有协调一致的性质。每个 5S rDNA 重复序列均由进化上保守的编码序列 (CDS) 和可变基因间隔区 (IGS) 组成。5S rDNA是研究重复序列分子进化的流行模型，IGS突变率高决定了其广泛应用于密切相关类群的系统发育分析。然而，许多高等植物的 5S rDNA 仍未被探索，特别是白花丹科 (Plumbaginaceae)。该科的一些类群是乌克兰南部特有的，并被列入红皮书。然而，它们的分类学地位存在争议，其澄清需要使用分子系统发育方法。在这项工作中，我们检查了柠檬科（白花丹科中最大的属）的四个属代表的 5S rDNA 分子组织。结果表明，补血草属、阿尔梅利亚属和角牛属的代表的 5S rDNA CDS具有不影响 5S rRNA 二级结构形成的单一突变。相比之下，在Goniolimon物种的基因组中，除了功能正常的5S rDNA重复之外，还发现了许多假基因，这些假基因不以一致的方式进化，并且在CDS中包含许多破坏5S rRNA二级结构的突变。Pteroclados 亚属和补血草属的补血草亚属的代表之间存在显着的系统发育距离，表明Pteroclados可以被认为是一个单独的属。分子进化的高速率使得 5S rDNA IGS 成为重建所研究的柠檬族属内的系统发育关系和乌克兰地方性柠檬属的条形码的便捷工具。