Journal Article

The Type-A Response Regulator, ARR15, Acts as a Negative Regulator in the Cytokinin-Mediated Signal Transduction in <i>Arabidopsis thaliana</i>

Takatoshi Kiba, Hisami Yamada, Shusei Sato, Tomohiko Kato, Satoshi Tabata, Takafumi Yamashino and Takeshi Mizuno

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 8, pages 868-874
Published in print August 2003 | ISSN: 0032-0781
Published online August 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg108
The Type-A Response Regulator, ARR15, Acts as a Negative Regulator in the Cytokinin-Mediated Signal Transduction in Arabidopsis thaliana

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The Arabidopsis thaliana AHK4 histidine kinase (also known as CRE1 or WOL) acts as a cytokinin signal transducer, presumably, in concert with downstream components, such as histidine-containing phosphotransfer factors (AHPs) and response regulators (ARRs), through the histidine-to-aspartate (His→Asp) phosphorelay. Among 10 members of the type-A ARR family, the cytokinin-induced expression of ARR15 in roots is selectively impaired in the cre1-1 mutant, which carries a mutation in the AHK4 gene, suggesting a link between this type-A response regulator and the AHK4-mediated cytokinin signal transduction in roots. To address this issue further, we characterized a T-DNA insertion mutant of ARR15, and also constructed transgenic lines (referred to as ARR15-ox) that overexpress the ARR15 gene in a manner independent of cytokinin. While the T-DNA insertion mutant (arr15-1) showed no apparent phenotype, the cytokinin-independent overexpression of ARR15 in ARR15-ox plants resulted in a reduced sensitivity toward exogenously applied cytokinin, not only in elongation of roots in plants, but also in green callus formation (or shoot formation) in explants. Cytokinin-induced expressions of certain type-A ARRs were also down-regulated in ARR15-ox plants. These results support the view that ARR15 acts as a repressor that mediates a negative feedback loop in the cytokinin and AHK4-mediated His→Asp phosphorelay.

Keywords: Keywords: Arabidopsis — Cytokinin — Phosphorelay — Histidine kinase— Response regulator — Signal transduction.; Abbreviations: AHK, Arabidopsis histidine kinase; AHP, Arabidopsis histidine-containing phosphotransmitter; ARR, Arabidopsis response regulator.

Journal Article.  4044 words.  Illustrated.

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

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