Functions in the early stages of organ development by regulating cell division rate. Is probably involved in the regulation of a number of cell-cycle genes. May act as regulator of brassinosteroid (BR) signaling and cell-cycle controlling organ growth. Expressed in developing culm, coleoptile, primary root, young spikelet, young leaf blade and leaf sheath, floral meristem primordia, stamen primordia, and lemma and palea primordia. The protein kinase domain is predicted to be catalytically inactive. Dwarf plants with erect leaves. Reduced organ sizes due to decreased cell numbers resulting from reduced cell division rate. Xiao means small in Chinese. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.