The Studies On The Relationship Between Nucleolar Dynamic Structure And RDNA Distribution In Vicia Faba Cells

Nucleolus is the most prominent structural and functional domain in interphase nuclear of eukaryotic, in which assembly of ribosomes and processing of rRNA take place. The nucleolus is made up of three basic structure subcompartments: fibrillar centers (FCs), dense fibrillar components (DFCs), and granular components (GCs). The problem of the distribution and configuration of rDNA in the nucleoli of eukaryotic cells hasn't resolved for a long time. By conventional electron microscopy and cytochemical specific stain NAMA-Ur method in Vicia faba, we researched the relationship between the change of nucleolar structure and distribution of rDNA in nucleolar cycle. The clarification of the problem will make great signification on learning furtherly the relationship of nucleolar structure and function, rRNA genes transcription sites and efficient mechanism of transcription. The conclusions are as follows:1. In the cell cycle, the nucleolus began to emerge in telophase, it was small and had irregular shape in early G1 phase. It was bigger and usually ball, it had regular shape in S phase and G2 phase. During prophase the nucleolus became smaller, had no regular shape and disappeared gradually.2. In all the nucleolar cycle, nucleolar FCs and DFCs structure changed. In G1 phase FCs and DFCs appeared, they were few, there were usually heterogeneous FCs. In S phase FCs and DFCs were not obvious. In late S phase there were obvious FCs and DFCs distributing dispersely in the nucleoli. In G2 phase FCs and DFCs were seen clearly, the number increased. FCs became bigger, existed as homogeneous FCs and distributed dispersely. In late prophase, FCs and DFCs became smaller and fewer, FCs distributed regionalized. With the disintegration of nucleolus, FCs and DFCs disappeared gradually.3. In S phase, there was nucleoar vacuole in the nucleolus, the nucleolus-associated chromatin linked closely to the nucleolus, making the nucleoli rims appear hairy.4. The configuration of nucleolar rDNA varied. There was from condensed to decondensed, continuous and dynamic process. In G1 phase rDNA distributed in FCs, in condensed clumps. In S phase, FCs and DFCs were not obvious, rDNA arranged in dispersed decondensed forms and condensed clumps. In G2 phase and prophase, rDNA located in the borders of FCs and the junctions of FC/DFC, in condensed irregular clumps and the forms of surrounding FCs.