Probable plus end-directed motor protein that functions in the NACK-PQR (ANP1-MKK6-MPK4) MAP kinase signaling pathway, which is essential for somatic cell cytokinesis, especially for the cell-plate formation and its expansion. Regulates the activity and the localization of ANP1, probably by association through the non-catalytic region of the kinase. Functionally redundant with NACK2 and essential to promote the progression of cytokinesis and for cellularization (formation of the cell plate) during microgametogenesis and megagametogenesis. Expressed in roots, flowers, pollen mother cells and embryos. Expressed in a patchy pattern during embryogenesis. Phosphorylated at Thr-145, Thr-687 and Thr-703 by CDKAs and CDKBs. Phosphorylated NACK1 fails to mediate cytokinesis. Growth defects, dwarf plants with small, humped cotyledons and leaves. Development arrested at the vegetative stage without production of reproductive organs. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Kinesin family. KIN-7 subfamily.