Serine/threonine-protein kinase involved in the spatial and temporal control system organizing cortical activities in mitotic and postmitotic cells (PubMed:11489177). Required for the normal functioning of the plasma membrane in developing pollen. Involved in the regulation of cell expansion and embryo development (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Accumulates in the nucleolus during interphase (PubMed:15292395). Localized to the plasma membrane in developing pollen grains (By similarity). Expressed in both the sporophytic and the gametophytic tissues, especially in dividing cells. Expression is cell cycle-regulated, with higher expression in G2-M phases. Autophosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.