Fig. 2
From: Q&A: How do plants respond to cytokinins and what is their importance?
Diagram of the cytokinin two component system (TCS). AHKs (AHK2, AHK3 and AHK4/WOL1/CRE1) are autophosphorylated in response to cytokinins. The phosphoryl group is transferred to type-B ARRs through AHPs. Phosphorylated type-B ARRs bind to target DNA and induce the expression of a set of genes involved in cytokinin primary response. The stability of type-A ARRs, which repress cytokinin TCS signaling, is controlled through proteolysis by the 26S proteasome in a feedback loop. Expression of AHP6, which inhibits phosphotransfer between AHKs and canonical AHPs, is repressed by cytokinin. Red arrows indicate phosphotransfer. Blue solid arrows and T-end lines represent positive and negative regulation, respectively