Plays a role in conventional modes of cytokinesis in meristems and during male gametogenesis but also acts in nonconventional modes of cytokinesis (cellularization) during female gametogenesis. Constitutes a signaling module in association with Kinesin-12 members that is required to support phragmoplast expansion and cell-plate growth in plant cells. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with Kinesin-12 members KIN12A/PAKRP1 and KIN12B/PAKRP1L (PubMed:22709276). Interacts with KIN7B/NACK2 (PubMed:24146312). Localized to the midline of the nascent phragmoplast and remains associated with the expanding phragmoplast ring. Ubiquitous. The ARM-repeat containing C-terminal region is required for the binding to the Kinesin-12 members. Cytokinesis-defective leading to aberrant pollen and embryo sacs. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.