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首页> 外文期刊>Protoplasma: An International Journal of Cell Biology >Functional ultrastructure of the plant nucleolus
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Functional ultrastructure of the plant nucleolus

机译：植物核仁的功能超微结构

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摘要

Nucleoli are nuclear domains present in almost all eukaryotic cells. They not only specialize in the production of ribosomal subunits but also play roles in many fundamental cellular activities. Concerning ribosome biosynthesis, particular stages of this process, i.e., ribosomal DNA transcription, primary RNA transcript processing, and ribosome assembly proceed in precisely defined nucleolar subdomains. Although eukaryotic nucleoli are conservative in respect of their main function, clear morphological differences between these structures can be noticed between individual kingdoms. In most cases, a plant nucleolus shows well-ordered structure in which four main ultrastructural components can be distinguished: fibrillar centers, dense fibrillar component, granular component, and nucleolar vacuoles. Nucleolar chromatin is an additional crucial structural component of this organelle. Nucleolonema, although it is not always an unequivocally distinguished nucleolar domain, has often been described as a well-grounded morphological element, especially of plant nucleoli. The ratios and morphology of particular subcompartments of a nucleolus can change depending on its metabolic activity which in turn is correlated with the physiological state of a cell, cell type, cell cycle phase, as well as with environmental influence. Precise attribution of functions to particular nucleolar subregions in the process of ribosome biosynthesis is now possible using various approaches. The presented description of plant nucleolar morphology summarizes previous knowledge regarding the function of nucleoli as well as of their particular subdomains not only in the course of ribosome biosynthesis.
机译：核仁是几乎所有真核细胞中都存在的核域。它们不仅专门生产核糖体亚基，而且在许多基本的细胞活动中发挥作用。关于核糖体的生物合成，该过程的特定阶段，即核糖体DNA转录，初级RNA转录物加工和核糖体组装在精确定义的核仁亚域中进行。尽管真核细胞核仁在其主要功能方面是保守的，但在各个王国之间可以注意到这些结构之间明显的形态差异。在大多数情况下，植物核仁显示出井井有条的结构，其中可以区分出四个主要的超微结构成分：原纤维中心，致密的原纤维成分，颗粒成分和核仁液泡。核仁染色质是该细胞器的另一个重要的结构成分。核仁瘤虽然并非始终是明确区分的核仁结构域，但经常被描述为有充分基础的形态元素，尤其是植物核仁。核仁的特定子小室的比率和形态可以根据其代谢活性而变化，而代谢活性又与细胞的生理状态，细胞类型，细胞周期阶段以及环境影响相关。现在，可以使用多种方法将功能精确地分配给核糖体生物合成过程中的特定核仁亚区域。所呈现的植物核仁形态学描述总结了关于核仁及其特定亚结构域功能的先前知识，不仅在核糖体生物合成过程中。

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