title: Cytokinin-mediated control of leaf longevity by AHK3 through phosphorylation of ARR2 in Arabidopsis.
abstract: Cytokinins are plant hormones with profound roles in growth and development, including control of leaf longevity. Although the cytokinin signal is known to be perceived by histidine kinase receptors, the underlying molecular mechanism and specificity of the receptors leading to delayed leaf senescence have not yet been elucidated. Here, we found that AHK3, one of the three cytokinin receptors in Arabidopsis, plays a major role in controlling cytokinin-mediated leaf longevity through a specific phosphorylation of a response regulator, ARR2. This result was obtained through identification of a gain-of-function Arabidopsis mutant that shows delayed leaf senescence because of a missense mutation in the extracellular domain of AHK3. A loss-of-function mutation in AHK3, but not of the other cytokinin receptors, conferred a reduced sensitivity to cytokinin in cytokinin-dependent delay of leaf senescence and abolished cytokinin-dependent phosphorylation of ARR2. Consistently, transgenic overexpression of wild-type, but not an unphosphorylatable mutant ARR2, led to delayed senescence of leaves.
authors.affiliation: Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Hyo Jung
authors.initials: HJ
authors.lastname: Kim
authors.forename: Hojin
authors.initials: H
authors.lastname: Ryu
authors.forename: Sung Hyun
authors.initials: SH
authors.lastname: Hong
authors.forename: Hye Ryun
authors.initials: HR
authors.lastname: Woo
authors.forename: Pyung Ok
authors.initials: PO
authors.lastname: Lim
authors.forename: In Chul
authors.initials: IC
authors.lastname: Lee
authors.forename: Jen
authors.initials: J
authors.lastname: Sheen
authors.forename: Hong Gil
authors.initials: HG
authors.lastname: Nam
authors.forename: Ildoo
authors.initials: I
authors.lastname: Hwang
mesh_terms: D000375:Aging / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000071677:Histidine Kinase; D009154:Mutation; D010766:Phosphorylation; D018515:Plant Leaves / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C117139:ARR2 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D011494:Protein Kinases; D000071677:Histidine Kinase; C000605493:AHK3 protein, Arabidopsis