Necessary for male gametophyte development, as well as ovule specification and function. Involved in cell-cell communication process required during early anther development, and regulating cell division and differentiation to organize cell layers. Required for the development of high-ordered vascular strands within the leaf and a correlated control of leaf shape, size and symmetry. May regulate the CLV1-dependent CLV3-mediated signaling in meristems maintenance. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Self-interacts and interacts with BAM2 and CLV1. Binds to the CLV3, CLE5, CLE11, CLE18, CLE19, CLE22, CLE25, CLE26, CLE40, CLE41 and CLE42 mature peptides, probably via its extracellular leucine-rich repeat region. Expressed in seedlings, roots, leaves, inflorescences, flowers and siliques. Expressed in a ring surrounding the center of meristems extended in the cortex of developing stems and older pedicels. Present in all developing floral organs, especially in anthers and gynoecium. Observed in anthers at stage 2 in the archesporial cells. At stage 3, localized in the primary sporogenous and primary parietal cells. Subsequently preferentially expressed in the sporogenous cells at anther stage 4. Later restricted to the tapetum and pollen mother cells (PMCs) before disappearing progressively. Rescues partially CLV3 disruption. When associated with BAM2 disruption, abnormal anthers at a very early stage and later lack of endothecium, middle and tapetum layers. Loss of stem cells at the shoot and flower meristems. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.