Journal Article

Nitrogen-Dependent Accumulation of Cytokinins in Root and theTranslocation to Leaf: Implication of Cytokinin Species that Induces GeneExpression of Maize ResponseRegulator

Kentaro Takei, Hitoshi Sakakibara, Mitsutaka Taniguchi and Tatsuo Sugiyama

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 1, pages 85-93
Published in print January 2001 | ISSN: 0032-0781
Published online January 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce009
Nitrogen-Dependent Accumulation of Cytokinins in Root and theTranslocation to Leaf: Implication of Cytokinin Species that Induces GeneExpression of Maize ResponseRegulator

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We have described the spatial and temporal accumulation pattern of various cytokinin species in roots, xylem sap and leaves during the resupply of nitrogen in maize. Upon addition of nitrate to nitrogen-depleted maize plants, isopentenyladenosine-5′-monophosphate (iPMP) started to accumulate in roots within 1 h preceding accumulation of trans-zeatin riboside-5′-monophosphate (ZMP), trans-zeatin riboside (ZR) and trans-zeatin (Z). In the xylem flow, both exudation rate of xylem sap and the concentration of the cytokinins increased, and ZR was the dominant species in the sap. In leaf tissue, the accumulation level of Z, which was the dominant form, started to increase 4 h after nitrate resupply to plants and the level was maintained for at least 24 h. Administration of a near physiological concentration of Z, ZR or ZMP (Z-type cytokinins) to detached leaves induced the accumulation of ZmRR1 transcript, that encode maize response regulators, but administration of isopentenyladenine, isopentenyladenosine or iPMP did not. These results strongly suggest that cytokinins are transported across the roots to shoots in response to nitrogen availability, and that, most probably, Z-type cytokinin(s), trigger the induction of ZmRR1.

Keywords: Key words: Cytokinin — Nitrogen availability — Translocation — Xylem sap — Zea mays.; Abbreviations: AK, adenosine kinase; APRT, adenine phosphoribosyltransferase; BA, benzyladenine; BAMP, benzyladenosine-5′-monophosphate; BAR, benzyladenine riboside; BSA, bovine serum albumin; cis-Z, cis-zeatin; DZ, dihydrozeatin; DZR, dihydrozeatin riboside; ELISA, enzyme-linked immunosorbent assay; iP, isopentenyladenine; iPA, isopentenyladenosine; iPMP, isopentenyladenosine-5′-monophosphate; IPT, isopentenyl transferase; K, kinetin; LC, liquid chromatography; MS, mass spectrometry; PBS, phosphate-buffered saline: Z, trans-zeatin; ZMP, trans-zeatin riboside-5′-monophosphate; ZR, trans-zeatin riboside; Z7G, trans-zeatin-7-glucoside; Z9G, trans-zeatin-9-glucoside.

Journal Article.  6115 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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