A simple method for identification of S phase nuclei in Vicia faba root meristems using BrdUrd labeling and indirect immunofluorescence (comparison with H-3-thymidine incorporation)

A modified immunocytochemical method for identification of S-phase cells in root meristems is desribed. The technique combines incorporation of BrdUrd , rapid isolation of cell nuclei and indirect immunocytochemical detection of BrdUrd-labeled areas of chromatin using monoclonal anti-BrdUrd (I) and F ITC-conjugated (II) antibodies. The labeling indexes calculated using H-3-t hymidine autoradiography and BrdUrd-immunofluorescence in root meristems of Vicia faba subsp. minor were found comparable. However, the increased sens itivity of fluorescent staining reveals an enhanced complexity of visible s tructure emerging during successive periods of S-phase, allowing for discri minating not only quantitative but also qualitative aspects of nuclear labe ling patterns characteristic for specific periods of DNA replication.