FREE, CONJUGATED, AND BOUND POLYAMINES DURING THE CELL-CYCLE OF SYNCHRONIZED CELL-SUSPENSION CULTURES OF NICOTIANA-TABACUM

Changes in putrescine (Put) and spermidine (Spd) content were investigated in relation to the cell cycle of Nicotiana tabacum cell suspension cultures. In asynchronously dividing cells free and bound Put levels were significantly elevated during the exponential growth phase. Only poor or no correlations with cell division activity have been observed for conjugated polyamines and free or bound Spd. In experiments employing aphidicolin-synchronized cell cultures free and bound Put concentrations correlated closely with specific phases of the cell cycle, which were examined by flow cytometry. Free Put levels were highest at the end of G1 and at the S/G2 boundary but rapidly declined at the beginning of DNA replication. The changes in the titers found for bound Put paralleled those of the free form with the exception that the second increase was somewhat delayed, so that bound Put concentrations peaked during the G2/M phase. The significance of these changes with regard to the cell cycle is discussed. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.