Journal Article

Regulation of Sulfur-Responsive Gene Expression by Exogenously Applied Cytokinins in <i>Arabidopsis thaliana</i>

Naoko Ohkama, Kentaro Takei, Hitoshi Sakakibara, Hiroaki Hayashi, Tadakatsu Yoneyama and Toru Fujiwara

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 12, pages 1493-1501
Published in print December 2002 | ISSN: 0032-0781
Published online December 2002 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcf183
Regulation of Sulfur-Responsive Gene Expression by Exogenously Applied Cytokinins in Arabidopsis thaliana

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Effects of plant hormones on a sulfur-deficiency responsive element (βSR) from the promoter region of the β subunit gene of β-conglycinin, a major seed storage protein of soybean, were investigated using transgenic Arabidopsis thaliana. Among the hormones tested, the cytokinins, trans-zeatin (Z) and trans-zeatin riboside, upregulated gene expression directed by the βSR element both in the presence and in the absence of sulfate in the medium. Z also increased transcript accumulation of two endogenous sulfur-responsive genes, the adenosine 5′-phosphosulfate reductase (APR1) and the Sultr2;2, a sulfate transporter. Concentrations of cytokinins were unaltered during early stages of sulfur starvation when expression of these genes was upregulated. Z did not alter concentrations of O-acetyl-L-serine, a positive regulator of gene expression in sulfur starvation response. Concentrations of sucrose, which is known to upregulate expression of APR1, were increased in rosette leaves by Z. Sucrose application to the medium also increased expression directed by the βSR element, although sucrose concentrations in tissues were not significantly altered by sulfur availability. These results suggest that exogenously applied cytokinins positively regulate expression of these sulfur responsive genes through a pathway independent of that from sulfur starvation, possibly through increasing sucrose concentrations in tissues.

Keywords: Keywords: APR 1 — Arabidopsis thaliana — Cytokinin — Sucrose — Sulfur deficiency — Sultr2;2.; Abbreviations: APR, adenosine phosphosulfate reductase; βSR, sulfur-responsive promoter region of the gene of the β subunit of β-conglycinin; CaMV, cauliflower mosaic virus; GFP, green fluorescent protein; iP, isopentenyladenine; OAS, O-acetyl-L-serine; ORF, open reading frame; Z, trans-zeatin; ZR, trans-zeatin riboside.

Journal Article.  5343 words.  Illustrated.

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

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