Acts as a receptor histidine kinase for the cytokinin SDF-2 in a signal transduction pathway that regulates prestalk gene expression and controls terminal differentiation of prespore cells. Binding of SDF-2 to this protein inhibits phosphorelay and induces rapid sporulation. This protein undergoes an ATP-dependent autophosphorylation at a conserved histidine residue in the kinase core, and a phosphoryl group is then transferred to a conserved aspartate residue in the receiver domain. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Interacts with SDF-2, an acbA peptide involved in sporulation. Expressed from 8 hours following initiation of development, prior to the appearance of mound tips. Subsequently persists throughout development.