Abstract
The histidine kinases (designated as AHK2-AHK4) serve as primary receptors for one of the classical plant hormones, cytokinin. In addition to these cytokinin receptors, Arabidopsis has a number of phosphorelay components (e.g., AHP and ARR), which together constitute a cytokinin-responsive His-to-Asp phosphorelay signaling circuitry. Nonetheless, nothing is known about downstream components of the cytokinin-mediated phosphorelay circuitry. To identify such cytokinin-associated genes, we carried out extensive microarray analyses, as will be presented elsewhere (Kiba, Yamashino et al.). The results revealed a number of interesting genes. Here we selected and characterized an intriguing set of such cytokinin-responsive genes in details, including expression profiles, characterization of each T-DNA insertion mutant and transgenic line overexpressing a give gene. Characterized are: certain ERF family transcription factors (At2g46310, At4g23750), a AS2 (or LOB) family member (At1g16530), a GATA-type zinc finger protein (At4g26150), etc. The results will be discussed in the context of the cytokinin-mediated phosphorelay circuitry.
