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Identification of CRE1 as a cytokinin receptor from Arabidopsis


Cytokinins are a class of plant hormones that are central to the regulation of cell division and differentiation in plants1,2. It has been proposed that they are detected by a two-component system, because overexpression of the histidine kinase gene CKI1 induces typical cytokinin responses3 and genes for a set of response regulators of two-component systems can be induced by cytokinins4,5. 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 plants6,7,8,9. 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.

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M. Higuchi carried out most of the yeast work. We thank H. Saito for yeast strains, E. Kemper for pGPTV-KAN and K. Torii for comments. Seeds of abi3-1, aux1-7 and ein2-1 were obtained from ABRC. p415CYC was obtained from ATCC. This study was in part supported by grants from the Ministry of Education, Science and Culture of Japan, and from the Science and Technology Agency to T.K.

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Correspondence to Tatsuo Kakimoto.

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Supplementary Information for Figure 2 and 6 Supplementary Figures and Legends.

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Figure 1: Callus growth of the cytokinin-resistant mutant cre1-1 in different auxin and cytokinin concentrations.
Figure 2: Root growth of the cre1-1, cre1-2 and hormone-related mutants in the presence of various plant hormones.
Figure 3: Complementation of cre1-1 by CRE1.
Figure 4: Cytokinin-dependent growth phenotype of yeast in which SLN1 had been replaced with CRE1.


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