Plus-end directed kinesin-like motor enzyme that plays a critical role in the organization of phragmoplast microtubules during cytokinesis. Constitutes a signaling module in association with serine/threonine-protein kinase TIO that is required to support phragmoplast expansion and cell-plate growth in plant cells. Binds microtubules in an ATP-sensitive manner. Homodimer and heterodimer with KIN12B. Interacts with TIO. Localized to the midline of the nascent phragmoplast (late anaphase) and remains associated with the expanding phragmoplast ring. No visible phenotype. Kin12a and kin12b double mutant display defective pollen grains leading to the production of fewer seeds. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Kinesin family. KIN-12 subfamily. The predicted gene has been split into 3 genes: At4g14145, At4g14147 and At4g14150. The predicted gene has been split into 3 genes: At4g14145, At4g14147 and At4g14150.