Distribution of DNA and localization of rRNA transcription in rnG2 phase nucleolus of Physarum polycephalum

摘要

Using electron microscopy, NAMA-Ur DNA selective staining and BrUTP incorporation, the nucleornlus ultrastructure, the distribution of DNA and the rRNA transcription sites in nucleolus of G2 phase Physarum polyrncephalum were studied. The nucleolus was found to be different in structure from that of other plant cells. Fibrillar cenrntern (FCs) were present in a large amount all over the nucleolus. DNA was distributed both in dense fibrillar components rn(DFC) and in FC. The DNA in the nucleolus was less condensed than that of the chromosome territory. These changes rnsuggested that the transcription was active within the nucleolus. BrUTP incorporation localized the rRNA transcription in rnDFC and at the interface of FC and DFC, suggesting that the DNA in FC is in a storage form and only the rDNA in DFC rnis transcribed.