Abstract
Nuclear positioning is important for cell division and cell differentiation in plants. In tobacco BY-2 cells, it has been reported that the pre-mitotic nuclear migration from the periphery to the central region of the cell requires both microfilaments (MFs) and microtubules and that the migration of daughter cell nuclei away from the newly formed cell wall is depend mainly on MFs. However, further molecular mechanisms of these nuclear migration events are not known. Here we report the identification of a strong candidate for the nuclear migrating motor, designated NMK-1, by molecular cloning of cDNAs encoding kinesin related proteins and localization studies using GFP-fused proteins. The full-length NMK-1:GFP fusion protein localized to nuclear surface through out the cell cycle in BY-2 cells. The expression of various truncated NMK-1 proteins revealed that NMK-1 associates to nuclear surface via its coiled coil domain. The induced expression of a rigor mutant of NMK-1 resulted in an accumulation of cell pairs in which daughter nuclei were associated with newly formed cell wall, indicating that the rigor mutant NMK-1 inhibited the migration of daughter nuclei after cytokinesis.
