Ultrastructural localization of active genes in Allium cepa cells

By using the anti-RNA/DNA hybrid antibody as the probe, we labeled and anal yzed the precise transcriptional 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 concentrate d at the central matrix space where there were no cristae and thylakoids. I n the extranucleolar regions of nucleus, the labeled signals of transcripti onal sites were situated at the perichromatin fibrils, which decondensed an d 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 Alli um 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.