Probable serine-threonine kinase that may act as a negative regulator of brassinosteroid (BR) signaling during flower development. May have physiological roles in stress signal-transduction pathways (PubMed:17690841). Phosphorylates LIC in response to BR perception (PubMed:22570626). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with LIC. Highly expressed in the entire young panicles, spikelets, awns, vascular bundles of palea and lemma, stigma and rachilla. Expressed in root tips, root hairs, lamina joint in the collar region, vascular bundles of coleoptiles. Induced by cold and salt stresses. Down-regulated by drought stress. Increased length of spikelet awns and weight of seeds. Increased sensitivity to brassinolide. Enhanced tolerance to drought, salt, cold and heat stresses. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. GSK-3 subfamily.