J Integr Plant Biol. ›› 1989, Vol. 31 ›› Issue (1): -.

• Research Articles •    

Studies on the Mininucleolus in Nuclei of Meristematic Cells of Vicia faba

Xing Miao, Hao Shui and Tong De-juan   

Abstract: A small intranuclear body, termed spherule, mininucleolus, karyosome, nuclear body or coiled body, has been reported in the cell of higher plants. This intranuclear body has been suggested to represent products of transcription, to correspond to the complex of transcription, or to be related to the RNA metabolism after transcription. Opinions on its composition are diverse and the origin and functions of the body are still obscure. We studied this intranuclear body, called mininucleolus in our paper, and found that the body appeared as an ovoid or spherical structure about 0.3 to 0.5 μm in diameter. The mininucleolus was shown, with conventional TEM staining, to be the same electron-dense as the condensed chromatin, but no structural connections could be found between them. The results of Bernhard's staining and the protein specific staining indicated that the mininucleolus contained both RNA and proteins which formed ribonucleoprotein (RNP) particles about 15 μm in diameter. These particles are very similar, in their ultrastructure and chemical composition, to the granular components of the nucleolus. A careful examination revealed that the mininucleoli were formed in the granular region of the nucleolus. After they became separated from the nucleolus, these bodies were distributed throughout the nucleoplasm, suggesting that they may move from the nucleolus to the nuclear membrane. Based on these data, we suggest that the mininucleolus is a non-chromatin intranuclear structure which is formed in the nucleolus and may have a function of transporting ribosomal RNA from the nucleolus to the cytoplasm.

Key words: icia faba, Mininucleoli: Nucleoli, Ribosomal RNA

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