Receptor with a serine/threonine-protein kinase activity required for the specification of the correct number of male archesporial initials and for the subsequent specification of tapetal and middle cell layer identities. In seeds, required for enhancing cell size and the rate of embryonic development. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with TPD1. Present in young buds, open flowers and siliques but absent from mature leaves and roots. Strongly expressed in the young organ primordia, and as the anthers and ovules developed, became focused in the microsporangia and in the distal and chalazal regions of the ovule. In cv. Landsberg erecta, only expressed in the anthers of young floral buds. Expressed during the differentiation of microsporocytes and tapetal cells. Also expressed in the meiocytes and young pollen grains until pollen mitosis II. Autophosphorylates in vitro. Some ecotypic variation may occur: in cv. Landsberg erecta, meiocytes of a null mutant fail to undergo cytokinesis while in cv. C24, cytokinesis clearly takes place, with the mutant meiocytes degenerating shortly after the tetrad stage. In cv. C24, the gene is expressed in the young ovular primordia, but the protein is not present in these organs. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.