Journal Article

<i>AtIPT3</i> is a Key Determinant of Nitrate-Dependent Cytokinin Biosynthesis in <i>Arabidopsis</i>

Kentaro Takei, Nanae Ueda, Koh Aoki, Takashi Kuromori, Takashi Hirayama, Kazuo Shinozaki, Tomoyuki Yamaya and Hitoshi Sakakibara

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 8, pages 1053-1062
Published in print August 2004 | ISSN: 0032-0781
Published online August 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch119
AtIPT3 is a Key Determinant of Nitrate-Dependent Cytokinin Biosynthesis in Arabidopsis

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We analyzed the spatial expression pattern of Arabidopsis thaliana adenosine phosphates-isopentenyltransferase genes (AtIPT1, AtIPT3 to AtIPT8) and the effect of inorganic nitrogen sources on their regulation. In mature plants, the AtIPTs were differentially expressed in various tissues including the roots, leaves, stems, flowers and siliques. In transgenic seedlings expressing a gene for green fluorescent protein (GFP) driven by the AtIPT promoters, AtIPT1::GFP was predominantly expressed in the vascular stele of the roots, AtIPT3::GFP was in the phloem companion cells, AtIPT5::GFP was in the lateral root primordium and pericycle, and AtIPT7::GFP was in both the vascular stele and the phloem companion cells of the roots. In a long-term treatment, the accumulation level of AtIPT5 transcript was correlated with the concentrations of NO3 and NH4+ in the growth medium. However, under nitrogen-limited conditions, AtIPT3 expression was rapidly induced by NO3 in the seedlings accompanying the accumulation of cytokinins, whereas AtIPT5 expression was little affected. The NO3-dependent accumulation of both the AtIPT3 transcript and the cytokinins was markedly reduced in a Ds transposon-insertion mutant of AtIPT3. These results suggest that nitrogen availability differentially regulates expression of AtIPT3 and AtIPT5, and that AtIPT3 is a key determinant of cytokinin biosynthesis in response to rapid changes in the availability of NO3.

Keywords: Keywords: Ammonium ions — Arabidopsis — Cytokinin — Isopentenyltransferase — Nitrate ions.; Abbreviations: AtIPT, Arabidopsis thaliana adenosine phosphates-isopentenyltransferase genes; CK, cytokinin; cZ, cis-zeatin; GFP, green fluorescent protein; iP, isopentenyladenine; iPR, isopentenyladenine riboside; iPRMP, isopentenyladenine riboside 5′-monophosphate; tZ, trans-zeatin; tZR, trans-zeatin riboside; tZRMP, trans-zeatin riboside 5′-monophosphate.

Journal Article.  6114 words.  Illustrated.

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

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