Functions as 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. Type-A response regulators seem to act as negative regulators of the cytokinin signaling. Weakly expressed in flowers and panicles. By cytokinin in roots and leaves. 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. Dwarf, narrow leaf, low tillering and altered kernal color phenotypes. Belongs to the ARR family. Type-A subfamily.