title: An Arabidopsis histidine-containing phosphotransfer (HPt) factor implicated in phosphorelay signal transduction: overexpression of AHP2 in plants results in hypersensitiveness to cytokinin.
abstract: 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.
authors.affiliation: Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Kuniko
authors.initials: K
authors.lastname: Ishikawa
authors.forename: Takafumi
authors.initials: T
authors.lastname: Yamashino
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mizuno
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism*; D003583:Cytokinins / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005030:Ethylenes / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006639:Histidine / Q000378:metabolism*; D018546:Hypocotyl / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D010766:Phosphorylation / Q000187:drug effects; D010770:Phosphotransferases; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D015398:Signal Transduction / Q000187:drug effects; D015026:Zeatin / Q000494:pharmacology
chemical_list: C117967:AHP2 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; D005030:Ethylenes; D010937:Plant Growth Regulators; D010940:Plant Proteins; D001224:Aspartic Acid; D006639:Histidine; D015026:Zeatin; C036216:ethylene; D010770:Phosphotransferases