Centromeres in eukaryotes mediate the accurate segregation of chromosomes during cell division. They serve as essential functional units of chromosomes and play a core role in the process of genome evolution. Centromeres are composed of satellite repeats and highly repetitive centromeric retrotransposons (CRs), which vary greatly even among closely related species. Cucumber (Cucumis sativus) is a globally cultivated and economically important vegetable and the only species in the Cucumis genus with seven pairs of chromosomes. Therefore, studying the centromeres of the Cucumis subgenus may yield valuable insights into its genome structure and evolution. Using chromatin immunoprecipitation (ChIP) techniques, we isolated centromeric DNA from cucumber reference line 9930. Our investigation into cucumber centromeres uncovered the centromeric satellite sequence, designated as CentCs, and the prevalent of Ty1/Copia long terminal repeat (LTR) retrotransposons. In addition, active genes were identified in the CsCENH3 nucleosome regions with low transcription levels. To the best of our knowledge, this is the first time that characterization of centromeres has been achieved on cucumber. Meanwhile, our results on the distribution of CentCs and CsCRs in the subgenus Cucumis indicate that the content of centromeric repeats in the wild variants was significantly reduced compared to the cultivated cucumber. The results provide evidence for centromeric DNA amplification that occurred during the domestication process from wild to cultivated cucumber. Furthermore, these findings may offer new information for enhancing our understanding of the phylogenetic relationship in the Cucumis genus.

中文翻译：

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CsCENH3 蛋白和着丝粒 DNA 谱的表征揭示了黄瓜着丝粒的结构


真核生物中的着丝粒在细胞分裂过程中介导染色体的精确分离。它们作为染色体的重要功能单位，在基因组进化过程中发挥核心作用。着丝粒由卫星重复序列和高度重复的着丝粒逆转录转座子（CR）组成，即使在密切相关的物种之间，其差异也很大。黄瓜（Cucumis sativus）是一种全球栽培的重要经济蔬菜，也是黄瓜属中唯一具有七对染色体的物种。因此，研究黄瓜亚属的着丝粒可能对其基因组结构和进化产生有价值的见解。使用染色质免疫沉淀 (ChIP) 技术，我们从黄瓜参考系 9930 中分离出着丝粒 DNA。我们对黄瓜着丝粒的研究发现了着丝粒卫星序列（称为 CentCs），以及普遍存在的 Ty1/Copia 长末端重复序列 (LTR) 反转录转座子。此外，在 CsCENH3 核小体区域中鉴定出转录水平较低的活性基因。据我们所知，这是首次在黄瓜上实现着丝粒的表征。同时，我们对黄瓜亚属CentCs和CsCRs分布的结果表明，与栽培黄瓜相比，野生变种中着丝粒重复的含量显着降低。这些结果为从野生黄瓜到栽培黄瓜的驯化过程中发生的着丝粒 DNA 扩增提供了证据。此外，这些发现可能为增强我们对黄瓜属系统发育关系的理解提供新信息。