Croissance et synthese des proteines de suspensions cellulaires de Tabac sensibles à la kinétine

Culture conditions, allowing the unlimited growth and maintenance in shaken suspensions of a kinetin dependent strain of tobacco pith cells, were determined. Cell clusters from 1 to 25 cells were selected from the cultures to study the cell multiplication after addition of specific growth factors to the basal medium. Cell division was found to be strictly dependent upon the presence in the medium of both kinetin and auxin. In complete medium the generation period was 45 to 49 hours. Kinetics of the total protein synthesis in the cell suspensions have been measured either by estimation of protein nitrogen or by ³⁵S incorporation into the proteins. After 3 days of culture, growth was exponential, as expressed by cell number or protein synthesis, which varied proportionally. Evidence was also found that the initial incorporation rate of radioactivity into the proteins was more rapid than expected from the increment of the protein net weight. It seems therefore reasonable to assume that a significant amount of protein turn over does exist during the initial period of growth. This phenomenon was observed even when no cell division occurred. Kinetin significantly activated protein synthesis, whether or not auxin was present in the medium.