Cytokinin signaling pathway starts from receiving of the ligand (cytokinin) by the cytokinin receptors (a dimer), followed by a phosphate relay by acceptor and donor domains of the receptors and then the histidine phosphotransmitters (HPs). HPs activate the type-A and type-B Arabidopsis response regulators (ARRs) to initiate the downstream events in cytokinin mediated response. Caesar et al (2011) show receptor location in the endoplasmic reticulum membrane, though all the classical models show them on plasma membrane.
Paralogs from the A. thaliana genome for AHKs, AHPs, Type-A and Type-B ARRs were added as group members (not as members of complex) on the pathway diagram.