Transcriptional activator that binds specifically to the DNA sequence 5'-[AG]GATT-3'. Functions as a response regulator involved in His-to-Asp phosphorelay signal transduction system. Phosphorylation of the Asp residue in the receiver domain activates the ability of the protein to promote the transcription of target genes. Could directly activate some type-A response regulators in response to cytokinins. Involved in the expression of nuclear genes for components of mitochondrial complex I. Promotes cytokinin-mediated leaf longevity. Involved in the ethylene signaling pathway in an ETR1-dependent manner and in the cytokinin signaling pathway. Binds the target DNA as a monomer (By similarity). Interacts with histidine-containing phosphotransfer proteins. Detected in the whole plant. Predominantly expressed in pollen. Two-component system major event consists of a His-to-Asp phosphorelay between a sensor histidine kinase (HK) and a response regulator (RR). In plants, the His-to-Asp phosphorelay involves an additional intermediate named Histidine-containing phosphotransfer protein (HPt). This multistep phosphorelay consists of a His-Asp-His-Asp sequential transfer of a phosphate group between first an His and an Asp of the HK protein, followed by the transfer to a conserved His of the HPt protein and finally the transfer to an Asp in the receiver domain of the RR protein. Phosphorylated in response to cytokinin mediated by AHK3. Retarded growth and development, and early flowering. Reduced responses to ethylene and cytokinin. Belongs to the ARR family. Type-B subfamily. Artifacts of PCR amplification.