Could be involved in the negative regulation of root growth. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with KIPK1 AND KIPK2 (via its cytosolic domain). Mostly expressed in roots, inflorescence bolts and flower buds. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.