Bromodeoxyuridine DNA fiber technology in plants: replication origins and DNA synthesis in tobacco BY-2 cells under prolonged treatment with aphidicolin

Summary. Newly synthesized DNA can be observed on chromosomes or extended chromatin fibers after incorporation and immunodetection of bromodeoxyuridine. This technique, frequently used in animal cells, was adapted for use in BY-2 cells. For the first time, the origins of replication in plant cells could be visualized and monitored on DNA fibers without the use of radioactive traces. The replicon size for BY-2 cells was estimated to be 12.9 µm; and the fork rate, 1.17 µm/h. These values are comparable to those reported for tomato and mustard cells. Furthermore, the data confirm our previous observation that DNA synthesis is not totally blocked by aphidicolin. Bromodeoxyuridine incorporation into DNA was obvious from 24 h onwards after treatment with aphidicolin.Correspondence and reprints: Department of Biology, Universitaire Instelling Antwerpen, Universiteitsplein 1, 2610 Wilrijk, Belgium.