Abstract
It was recently demonstrated that certain histidine kinases (designated as AHK2-AHK4) serve as primary receptors for one of the classical plant hormones, cytokinin. In addition to these cytokinin receptors, Aravidopsis has a number of phosphorelay components (e.g., AHP and ARR), which together constitute a cytokinin-responsive His-to-Asp phosphorelay signaling circuitry. The hallmarked cytokinin-induced genes are ARRs encoding type-A response regulators. Otherwise, nothing is known about downstream components of the cytokinin-mediated phosphorelay circuitry. To identify such cytokinin-associated genes, we carried out extensive microarray analyses by employing not only wild-type plants but also transgenic plants, in which the cytokinin-mediated phosphorelay circuitry was genetically manipulated (e.g., ARR21-C-ox, ARR22-ox). The results of such combinatorial microarray analysis revealed a number of interesting genes, each of which was rapidly upregulated in response to cytokinin through His-to-Asp phosphorelay. By logically explaining the strategy of such combinatorial microarray analysis, the genome-wide list of cytokinin-induced genes will be presented.
