Temporal Control of Differentiation by the Cell Nucleus: Evidence for a Species-Specific Nuclear Suppression of Enzymes at the Early Generative Phase in Acetabularia

Abstract

The role of the cell nucleus in controling steps of differentiation has been revealed by comparing nucleate and anucleate cells of Acetabularia (Berger et al. 1987; Bonotto, 1988). In all cases investigated so far, events related to the generative phase of the life cycle are expressed earlier in anucleate cells. Consequently, the existence of a nuclear suppressor delaying the onset of generative functions in the intact cell has been postulated (Bannwarth and Schweiger, 1983). In order to determine whether this nuclear action is species-specific, the nucleus of the species Acetabularia acetabulum was replaced by a nucleus of the species Acetabularia crenulata. The foreign nucleus did not suppress the increase in dCMP deaminase (EC 3.5.4.12) enzyme activity. This result indicates that the suppression by the nucleus is species-specific.