Ultrastructural localization of intranucleolar DNA in Vicia faba root-tip cells by immunocytochemistry using an anti-BUdR antibody.

Ultrastructural localization of intranucleolar DNA in Vicia faba root-tip cells was investigated by an immunocytochemical method consisting of in vitro bromodeoxyuridine (BUdR)-labelling with the aid of terminal deoxynucleotidyltransferase and successive immunocytochemistry using an anti-BUdR antibody. The nucleolus usually had many low electron-opaque patches (LEPs). The fibrillar centers (FCs) occupied their peripheral region leaving a central electron-transparent space (central space). The immunoelectron microscopic technique showed that in the nucleolus the label was mostly confined to the FCs whilst the central space was completely free from the label. In other nucleolar regions the label appeared to gradually increase towards the FCs. In addition to nucleoli, this method also localized a small amount of DNA in mitochondria.