title: Heterogeneity of nuclear DNA labelling from intact, wounded and virus-infected tobacco leaves.
abstract: The nuclear DNA of tobacco leaves includes a major and a satellite fraction, with bouyant densities (rho) of 1.696 and 1.706 g/ml, respectively, in neutral CsCl gradients. On preparative ultracentrifugation, the major DNA presents 4 or 5 shoulders with lighter densities, between 1.695 and 1.686 g/ml. This heterogeneity was confirmed by several types of experiments. DNA synthesis after wounding or viral infection did not induce a new component. Specific radioactivity profiles of DNA show a large heterogeneity in [3H]thymidine labelling that confirms the non-mitotic character of this DNA synthesis. Two zones are highly radioactive: the first one corresponds to the major peak dense side of the DNA and the second one to the few dense minor components, leading to a significant increase of their proportion after infection.
mesh_terms: D002499:Centrifugation, Density Gradient; D004247:DNA / Q000302:isolation & purification*; D004276:DNA, Satellite / Q000302:isolation & purification*; D010947:Plants, Toxic; D013936:Thymidine / Q000378:metabolism; D014026:Nicotiana / Q000378:metabolism*; D014027:Tobacco Mosaic Virus; D014316:Tritium; D014777:Virus Diseases / Q000378:metabolism*
chemical_list: D004276:DNA, Satellite; D014316:Tritium; D004247:DNA; D013936:Thymidine