Constitutive heterochromatin typically exhibits low gene density and is commonly found adjacent or close to the nuclear periphery, in contrast to transcriptionally active genes concentrated in the innermost nuclear region. In Triatoma infestans cells, conspicuous constitutive heterochromatin forms deeply stained structures named chromocenters. However, to the best of our knowledge, no information exists regarding whether these chromocenters acquire a precise topology in the cell nuclei or whether their 18S rDNA, which is important for ribosome function, faces the nuclear center preferentially. In this work, the spatial distribution of fluorescent Feulgen-stained chromocenters and the distribution of their 18S rDNA was analyzed in Malpighian tubule cells of T. infestans using confocal microscopy. The chromocenters were shown to be spatially positioned relatively close to the nuclear periphery, though not adjacent to it. The variable distance between the chromocenters and the nuclear periphery suggests mobility of these bodies within the cell nuclei. The distribution of 18S rDNA at the edge of the chromocenters was not found to face the nuclear interior exclusively. Because the genome regions containing 18S rDNA in the chromocenters also face the nuclear periphery, the proximity of the chromocenters to this nuclear region is not assumed to be associated with overall gene silencing.

中文翻译：

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Triatoma infestans (Klug) 细胞核中异染色质体的空间分布

组成型异染色质通常表现出低基因密度，并且通常在核外围附近或附近发现，与集中在最内核区域的转录活性基因相反。在三叶虫细胞，显着的组成型异染色质形成称为染色中心的深染色结构。然而，据我们所知，尚无关于这些染色中心是否在细胞核中获得精确拓扑结构或它们对核糖体功能很重要的 18S rDNA 是否优先面向核中心的信息。在这项工作中，荧光 Feulgen 染色中心的空间分布及其 18S rDNA 的分布在马尔皮基小管细胞中进行了分析。T. infestans使用共聚焦显微镜。显示染色中心在空间上相对靠近核外围，但不与其相邻。chromocenters 和核外围之间的可变距离表明这些机构在细胞核内的移动性。未发现 18S rDNA 在染色中心边缘的分布仅面向核内部。由于染色中心中含有 18S rDNA 的基因组区域也面向核外围，因此不假定染色中心与该核区域的接近性与整体基因沉默相关。