Journal Article

An Arabidopsis Histidine-Containing Phosphotransfer (HPt) Factor Implicated in Phosphorelay Signal Transduction: Overexpression of AHP2 in Plants Results in Hypersensitiveness to Cytokinin

Tomomi Suzuki, Kuniko Ishikawa, Takafumi Yamashino and Takeshi Mizuno

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 1, pages 123-129
Published in print January 2002 | ISSN: 0032-0781
Published online January 2002 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcf007
An Arabidopsis Histidine-Containing Phosphotransfer (HPt) Factor Implicated in Phosphorelay Signal Transduction: Overexpression of AHP2 in Plants Results in Hypersensitiveness to Cytokinin

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Histidine-containing phosphotransfer (HPt) factors from Arabidopsis thaliana, designated as AHPs, function most likely in concert with histidine (His)-kinases (HKs) and response regulators (RRs) in certain multistep histidine (His)→aspartate (Asp) phosphorelays that are involved in the signal transduction mechanisms, by which plant cells appear to respond to certain hormonal stimuli, including cytokinin. Although some previous in vitro results from studies on Arabidopsis AHPs (AHP1 to AHP5) supported this hypothesis, it has not yet been proven. To this end, here we constructed transgenic plants that contained the AHP2 protein in a considerably higher amount than in wild-type plants. Such AHP2-overexpressing young seedlings were examined in comparison with wild-type plants, with special reference to hormone responses; particularly, their inhibitory effects on root elongation of plants grown on agar-plates, and also hypocotyl elongation of etiolated seedlings grown in the dark. The results of this study suggested that AHP2-overexpressing plants showed a characteristic phenotype of cytokinin-hypersensitive. These in vivo observations were best interpreted by assuming that the AHP factor(s) is somehow implicated, if not directly, in a cytokinin-mediated His→Asp phosphorelay signaling in Arabidopsis.

Keywords: Key words: Arabidopsis — Phosphorelay — HPt factor — His-kinase — Cytokinins.; Abbreviations: AHP, Arabidopsis histidine-containing phosphotransfer factor; AHK, Arabidopsis histidine kinase; ARR, Arabidopsis response regulator.

Journal Article.  4203 words.  Illustrated.

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

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