title: A novel regulatory pathway of sulfate uptake in Arabidopsis roots: implication of CRE1/WOL/AHK4-mediated cytokinin-dependent regulation.
abstract: Cytokinin is an adenine derivative plant hormone that generally regulates plant cell division and differentiation in conjunction with auxin. We report that a major cue for the negative regulation of sulfur acquisition is executed by cytokinin response 1 (CRE1)/wooden leg (WOL)/Arabidopsis histidine kinase 4 (AHK4) cytokinin receptor in Arabidopsis root. We constructed a green fluorescent protein (GFP) reporter system that generally displays the expression of the high-affinity sulfate transporter SULTR1;2 in Arabidopsis roots. GFP under the control of SULTR1;2 promoter showed typical sulfur responses that correlate with the changes in SULTR1;2 mRNA levels; accumulation of GFP was induced by sulfur limitation (-S), but was repressed in the presence of reduced sulfur compounds. Among the plant hormones tested, cytokinin significantly downregulated the expression of SULTR1;2. SULTR1;1 conducting sulfate uptake in sultr1;2 mutant was similarly downregulated by cytokinin. Downregulation of SULTR1;1 and SULTR1;2 by cytokinin correlated with the decrease in sulfate uptake activities in roots. The effect of cytokinin on sulfate uptake was moderated in the cre1-1 mutant, providing genetic evidence for involvement of CRE1/WOL/AHK4 in the negative regulation of high-affinity sulfate transporters. These data demonstrated the physiological importance of the cytokinin-dependent regulatory pathway in acquisition of sulfate in roots. Our results suggested that two different modes of regulation, represented as the -S induction and the cytokinin-dependent repression of sulfate transporters, independently control the uptake of sulfate in Arabidopsis roots.
authors.affiliation: RIKEN Plant Science Center, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Maruyama-Nakashita
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yamaya
authors.forename: Hideki
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D003583:Cytokinins / Q000502:physiology*; D017931:DNA Primers; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D000071677:Histidine Kinase; D007210:Indoleacetic Acids / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D013431:Sulfates / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D017931:DNA Primers; D007210:Indoleacetic Acids; D008164:Luminescent Proteins; D010937:Plant Growth Regulators; D011956:Receptors, Cell Surface; D013431:Sulfates; D049452:Green Fluorescent Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase; C421783:WOL protein, Arabidopsis