Abstract
Results of recent studies on Arabidopsis thaliana, the His-Asp phosphorelay signaling plays an essential role in the primary responses of plants to cytokinin. The phosphorelay circuitry consists of His-kinases (AHKs), phosphotransfer factors (AHPs), and transcription factors (type-B ARRs). Clarification of the downstream signaling network must await further extensive examination, which should include a comprehensive genetics of 11 type-B ARR genes. Here we isolated a set of mutant alleles, including arr1, arr10, arr12, arr13 and arr21. Plants carrying each one of these mutant alleles were characterized with reference to the inhibition of root elongation and the stimulation of callus development by cytokinin. The results suggested that the ARR1, ARR10, and ARR12 genes are more critically implicated in these cytoinin-responses. Then, an arr10/arr12 double mutant was selectively characterized deeper, by also employing a DNA microarray analysis. The results will be discussed with regard to the His-Asp phophorelay-mediated cytokinin-signaling network.
