Role of perinuclear microtubules in nuclear migration following cytokinesis of tobacco BY-2 cells

In plant cells, the daughter nuclei produced by mitosis migrate away from the cell plate following cytokinesis. It has been reported that this migration requires actin filaments and microtubules. However, the precise molecular mechanism remains unclear. In this study, we conducted time-lapse observations of tobacco BY-2 cells, in which microtubules and nuclei were visualized. Observations in cells of varying widths and lengths revealed that the rate of nuclear migration after cytokinesis differed significantly between cells. Cell width had a greater impact on migration speed than cell length, with narrower cells exhibiting more active nuclear migration. Perinuclear microtubules were more prominent in narrow cells with faster nuclear migration than in wider cells with slower migration. Additionally, observations in the presence of an actin-disrupting agent showed that in cells forming extra-phragmoplasts, as previously reported, daughter nuclei scarcely migrated even after the original phragmoplast disappeared. Conversely, in cells without extra-phragmoplasts, partial nuclear migration occurred. Interestingly, in cells with extra-phragmoplasts, perinuclear microtubules barely formed after the original phragmoplast disappeared, whereas in cells without extra-phragmoplasts, perinuclear microtubules formed after the original phragmoplast disappeared. These findings suggest that perinuclear microtubules play a crucial role in daughter nuclear migration.