Receptor kinase that may be involved in the regulation of cell proliferation and cell growth. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Reduced plant height, reduced panicle length and reduced seed set. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. Truncated N-terminus.