Characterization of the ARR15 and ARR16 response regulators with special reference to the cytokinin signaling pathway mediated by the AHK4 histidine kinase in roots of Arabidopsis thaliana.
The cytokinin receptor AHK4 histidine kinase, identified in Arabidopsis thaliana, presumably acts in concert with downstream components, such as histidine-containing phosphotransfer (HPt) factors (AHPs) and response regulators (ARRs). In this respect, we characterized a loss-of-function mutant of the AHK4 gene, named cre1-1, which showed a reduced cell number within the vascular tissues in roots. Among the 10 type-A ARR members, the expression of ARR15 and ARR16 in roots was specifically and markedly reduced in cre1-1, suggesting a link between these response regulators and the AHK4-mediated signal transduction in roots. The results for transgenic plants expressing promoter::GUS or promoter::LUC fusion genes showed that both the ARR15 and the ARR16 gene products are accumulated upon cytokinin treatment in roots. The results of GFP-fusion experiments with onion epidermal cells further showed that ARR15 was found in the nucleus, and ARR16 mainly in the cytoplasm. Together, it was suggested that ARR15 and ARR16 are distinctly implicated in the presumed AHK4-mediated signaling pathway in roots.
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D003583:Cytokinins / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D000071677:Histidine Kinase; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D019697:Onions / Q000235:genetics / Q000378:metabolism; D019441:Plant Epidermis / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
C470377:ARR15 protein, Arabidopsis; C470378:ARR16 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; D008164:Luminescent Proteins; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase; C421783:WOL protein, Arabidopsis