Jumping between histidine kinase receptors: the cytokinin transduction pathway

摘要

Cytokinins are a class of plant hormones that play a major role in the regulation of cell division and differentiation. Different lines of evidence suggest that they are detected by a two-component system. First, overexpression cfa histidine kinase gene, CKI1, induces typical cytokinin responses and second, several genes belonging to a set of response regulators of a two-component system can be induced by cytokinins. Two component systems, common in microorganisms and plants, use a histidine kinase as a sensor and transduce the signal by a phosphorylation cascade. Tsutomo Inoue etaL1 now report important progress in understanding cytokinin perception in Arabidopsis. The group screened mutagenized Arabidopsis for mutants that were impaired in cytokinin responses, including shoot formation in tissue culture and rapid cell proliferation. Using this genetic strategy, they isolated a mutant designated cytokinin response 1-1 (crel-1), which exhibited reduced responses to cytokinin. The mutated gene crel encodes a histidine kinase. Furthermore, Arabidopsis has genes for two products, AHK2 and AHK3, which share high sequence similarity to CRE1. In addition, crel expression conferred a cytokinindependent growth phenotype on a yeast mutant that lacked the endogenous histidine kinase, SLN1.