The genus Urochloa P. Beauv. presents a prominent role in the tropical agricultural scenario being composed of species with different ploidy levels. Studies on the genomic relationship within this genus as well as specific analysis involving epigenetic marks are limited. The aim of the present study was to identify the cytosine methylation (5-mCyt) and histone H3 lysine 9 dimethylation (H3k9me2) in the different modulations of 45S ribosomal DNA (rDNA) sites in interphase nuclei and to associate these results with gene expression analysis in Urochloa ruziziensis (2n = 4x = 36), Urochloa brizantha cv. Marandu (2n = 4x = 36), and their respective interspecific hybrid H1863 (2n = 4x = 36). Immunolocalization techniques were performed in combination with Fluorescence in situ hybridization (FISH) for the location of the 45S rDNA sites. Predominantly, we observed intra- and perinucleolar sites, mostly hypomethylated and/or hyper/hypomethylated, decondensed or partially condensed. The gene expression analysis was performed qualitatively through the conventional PCR using complementary DNA and confirmed by the RT-qPCR technique and primers designed for the ITS-1 region of U. brizantha and U. ruziziensis. The molecular analyses performed on leaves showed that there is dominance of U. brizantha 45S rDNA gene expression on U. ruziziensis in the H1863 hybrid. In roots, the analyses showed that the 45S rDNA genes of the two parents are expressed in the hybrid genome. Thus, it is plausible to infer a tissue-specific nuclear dominance model in which the pattern of hypermethylated cytosine sites with heterochromatic marks and, therefore, silenced were mostly inherited from U. ruziziensis, whereas the rDNA originated from U. brizantha was characterized by cytosine and H3k9 hypomethylation.

中文翻译：

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与 Urochloa P. Beauv 核仁优势研究相关的表观遗传标记。

Urochloa P. Beauv 属。在由具有不同倍性水平的物种组成的热带农业情景中发挥着重要作用。对该属内基因组关系的研究以及涉及表观遗传标记的具体分析是有限的。本研究的目的是确定间期细胞核中 45S 核糖体 DNA (rDNA) 位点的不同调节中的胞嘧啶甲基化 (5-mCyt) 和组蛋白 H3 赖氨酸 9 甲基化 (H3k9me2)，并将这些结果与基因表达分析相关联在 Urochloa ruziziensis (2n = 4x = 36)、 Urochloa brizantha cv。Marandu (2n = 4x = 36)，以及它们各自的种间杂种 H1863 (2n = 4x = 36)。免疫定位技术与荧光原位杂交 (FISH) 结合用于 45S rDNA 位点的定位。主要是，我们观察到核仁内和核仁周位点，主要是低甲基化和/或高/低甲基化、去浓缩或部分浓缩。基因表达分析通过常规 PCR 使用互补 DNA 进行定性分析，并通过 RT-qPCR 技术和为 U. brizantha 和 U. ruziziensis 的 ITS-1 区域设计的引物进行确认。对叶子进行的分子分析表明，在 H1863 杂种中，U. brizantha 45S rDNA 基因表达在 U. ruziziensis 上占优势。在根部，分析表明两个亲本的 45S rDNA 基因在杂交基因组中表达。因此，推断组织特异性核优势模型是合理的，其中具有异色标记并因此沉默的高甲基化胞嘧啶位点的模式主要从 U. ruziziensis 遗传，