By using the anti-RNA/DNA hybrid antibody as the probe, we labeled and analyzed the precise transcrip-tional sites of active genes in Allium cepa cells in situ. The results showed that the location of labeled signals appeared in mitochondrion was the same as that in chloroplast, generally concentrated at the central matrix space where there were no cristae and thylakoids. In the extranucleolar regions of nucleus, the labeled signals of transcriptional sites were situated at the perichromatin fibrils, which decondensed and stretched out from the chromosome territories. Our results also displayed the concentrations of labeled signals in a certain region of nucleus, and this means that the gene transcription rich region actually existed in Allium cepa cells. In nucleolus, the synthetic sites of rRNA were localized not only to the periphery of fibrillar centers but also to the DFC near FC.
The location and configuration of nucleolar DNA have not been determined for a long time. In this paper, we have observed the nucleolar infrastructure and the character of nucleolar DNA in Allium cepa cells by conventional electron microscopy and the cytochemical NAMA-Ur DNA specific staining method. Furthermore, we have properly improved the NAMA-Ur method so as to analyze the location and configuration of nucleolar DNA in situ. Our results indicated that the nucleolar DNA in Allium cepa cells is mainly located at the border between fibrillar centers and dense fibribllar component, especially distributed in the configuration of encircling the fibrillar centers.
