Shekhovtsov S V, Efremov Ya R, Poluboyarova T V, Peltek S E
Kurchatov Genomic Center of ICG SB RAS, Novosibirsk, Russia.
Vavilovskii Zhurnal Genet Selektsii. 2021 Oct;25(6):647-651. doi: 10.18699/VJ21.073.
The size of the nuclear genome in eukaryotes is mostly determined by mobile elements and noncoding sequences and may vary within wide limits. It can differ signif icantly both among higher-order taxa and closely related species within a genus; genome size is known to be uncorrelated with organism complexity (the so-called C-paradox). Less is known about intraspecif ic variation of this parameter. Typically, genome size is stable within a species, and the known exceptions turn out be cryptic taxa. The Eisenia nordenskioldi complex encompasses several closely related earthworm species. They are widely distributed in the Urals, Siberia, and the Russian Far East, as well as adjacent regions. This complex is characterized by signif icant morphological, chromosomal, ecological, and genetic variation. The aim of our study was to estimate the nuclear genome size in several genetic lineages of the E. nordenskioldi complex using f low cytometry. The genome size in different genetic lineages differed strongly, which supports the hypothesis that they are separate species. We found two groups of lineages, with small (250-500 Mbp) and large (2300-3500 Mbp) genomes. Moreover, different populations within one lineage also demonstrated variation in genome size (15-25 %). We compared the obtained data to phylogenetic trees based on transcriptome data. Genome size in ancestral population was more likely to be big. It increased or decreased independently in different lineages, and these processes could be associated with changes in genome size and/or transition to endogeic lifestyle.
真核生物核基因组的大小主要由移动元件和非编码序列决定，并且可能在很宽的范围内变化。它在高阶分类群之间以及属内密切相关的物种之间可能有显著差异；已知基因组大小与生物体复杂性无关（即所谓的C值悖论）。关于这个参数的种内变异了解较少。通常，一个物种内的基因组大小是稳定的，已知的例外情况是隐存分类群。艾氏远东亚种复合体包含几个密切相关的蚯蚓物种。它们广泛分布于乌拉尔山脉、西伯利亚、俄罗斯远东地区以及相邻地区。这个复合体的特点是在形态、染色体、生态和遗传方面存在显著变异。我们研究的目的是使用流式细胞术估计艾氏远东亚种复合体几个遗传谱系的核基因组大小。不同遗传谱系中的基因组大小差异很大，这支持了它们是独立物种的假设。我们发现了两组谱系，基因组大小分别为小（250 - 500兆碱基对）和大（2300 - 3500兆碱基对）。此外，一个谱系内的不同种群在基因组大小上也表现出变异（15 - 25%）。我们将获得的数据与基于转录组数据的系统发育树进行了比较。祖先种群的基因组大小更可能较大。它在不同谱系中独立增加或减少，这些过程可能与基因组大小的变化和/或向内生生活方式的转变有关。
