Role of cytoskeletal components in the migration of nuclei during the cell cycle transition from G 1 phase to S phase of tobacco BY-2 cells

Abstract

Summary The organization of microtubules (MTs) was followed during the cell cycle transition from G 1 phase to S phase in cells that were released from a sequential treatment with aphidicolin and propyzamide. DNA synthesis was identified in the cells in which MTs were developing in the perinuclear regions and elongating toward the cell cortex. Observations using confocal laser scanning microscopy suggested that MTs were elongating along the previously developed cables of microfilaments (MFs). Disorganization of MFs by cytochalasin prevented the elongation of MTs, resulting in the accumulation of short MTs in the perinuclear regions. Migration of nuclei was prevented by cytochalasin treatment, suggesting that the principal intracellular structures responsible for the migration of nuclei are MFs, not MTs. Katsuta et al. (1990) claimed the contrary. This difference seems to have originated from the fact that the cells released from aphidicolin treatment used by Katsuta et al. (1990) were slightly ahead of the border between the G 1 phase and the S phase in the cell cycle, while cells released from a sequential treatment with aphidicolin and propyzamide used in this study proceeded in a more natural way.