Identification of CRE1 as a cytokinin receptor from Arabidopsis

Abstract

Cytokinins are a class of plant hormones that are central to the regulation of cell division and differentiation in plants. It has been proposed that they are detected by a two-component system, because overexpression of the histidine kinase gene CKI1 induces typical cytokinin responses and genes for a set of response regulators of two-component systems can be induced by cytokinins. Two-component systems use a histidine kinase as an environmental sensor and rely on a phosphorelay for signal transduction. They are common in microorganisms, and are also emerging as important signal detection routes in plants. Here we report the identification of a cytokinin receptor. We identified Arabidopsis cre1 (cytokinin response 1) mutants, which exhibited reduced responses to cytokinins. The mutated gene CRE1 encodes a histidine kinase. CRE1 expression conferred a cytokinin-dependent growth phenotype on a yeast mutant that lacked the endogenous histidine kinase SLN1 (ref. 10), providing direct evidence that CRE1 is a cytokinin receptor. We also provide evidence that cytokinins can activate CRE1 to initiate phosphorelay signalling.

Arabidopsis ABCG14 protein controls the acropetal translocation of root-synthesized cytokinins

“…5). Although this characteristic phenotypically resembles the behaviour of cytokinin receptor mutant line cre1/ahk4, in which the perception of cytokinin signals is defective in the root 36 , mechanistically it may be quite distinct. One possible explanation is that the already high abundance of cytokinins in roots of atabcg14 mutants, resulting from the defect in root-to-shoot translocation (Table 1), may compromise the sensitivity of the root meristem cells in perceiving the exogenously applied signal molecules.…”

“…Hormone treatments followed the method of Inoue et al 36 with minor modifications. Briefly, seeds of selected genotypes were sown on halfstrength MS medium containing BA, tZ, ACC or NAA with various concentrations.…”

SND1 Transcription Factor-Directed Quantitative Functional Hierarchical Genetic Regulatory Network in Wood Formation in Populus trichocarpa

“…Such systems have been used extensively to study plant signal transduction. The use of mesophyll protoplasts in these studies is appropriate because some signal transduction pathways highly active in mesophyll cells are conserved in many other meristematic cell types (Inoue et al, 2001;Sheen, 2001;Fujii et al, 2009). At the full transcriptome level, protoplasts from cells representing progressive developmental stages in the Arabidopsis root were used to establish a microarray-based global gene expression map linking gene activity to specific cell fates in root development (Birnbaum et al, 2003).…”

Embryogenesis: Pattern Formation from a Single Cell

“…The wooden leg (wol) mutation in the Arabidopsis Histidine Kinase4/CYTOKININ RE-SISTANT1/WOODEN LEG (AHK4/CRE1/WOL) gene results in reduced cell divisions in the root meristem and a dramatic reduction, or absence of, phloem tissues in the root and hypocotyl (Scheres et al, 1994). The AHK4/CRE1/WOL gene encodes a membrane associated two-component histidine kinase (Mahonen et al, 2000) and has been identifi ed as a cytokinin receptor by conferring cytokinin responsiveness to yeast cells, when inserted into an appropriate yeast signal transduction pathway (Inoue et al, 2001). Two closely related proteins, AHK2 and AHK3 have also been identifi ed as cytokinin receptors.…”