title: CTR1 phosphorylates the central regulator EIN2 to control ethylene hormone signaling from the ER membrane to the nucleus in Arabidopsis.
abstract: The gaseous phytohormone ethylene C(2)H(4) mediates numerous aspects of growth and development. Genetic analysis has identified a number of critical elements in ethylene signaling, but how these elements interact biochemically to transduce the signal from the ethylene receptor complex at the endoplasmic reticulum (ER) membrane to transcription factors in the nucleus is unknown. To close this gap in our understanding of the ethylene signaling pathway, the challenge has been to identify the target of the CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) Raf-like protein kinase, as well as the molecular events surrounding ETHYLENE-INSENSITIVE2 (EIN2), an ER membrane-localized Nramp homolog that positively regulates ethylene responses. Here we demonstrate that CTR1 interacts with and directly phosphorylates the cytosolic C-terminal domain of EIN2. Mutations that block the EIN2 phosphorylation sites result in constitutive nuclear localization of the EIN2 C terminus, concomitant with constitutive activation of ethylene responses in Arabidopsis. Our results suggest that phosphorylation of EIN2 by CTR1 prevents EIN2 from signaling in the absence of ethylene, whereas inhibition of CTR1 upon ethylene perception is a signal for cleavage and nuclear localization of the EIN2 C terminus, allowing the ethylene signal to reach the downstream transcription factors. These findings significantly advance our understanding of the mechanisms underlying ethylene signal transduction.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
authors.forename: Chuanli
authors.initials: C
authors.lastname: Ju
authors.forename: Gyeong Mee
authors.initials: GM
authors.lastname: Yoon
authors.forename: Jennifer Marie
authors.initials: JM
authors.lastname: Shemansky
authors.forename: David Y
authors.initials: DY
authors.lastname: Lin
authors.forename: Z Irene
authors.initials: ZI
authors.lastname: Ying
authors.forename: Jianhong
authors.initials: J
authors.lastname: Chang
authors.forename: Wesley M
authors.initials: WM
authors.lastname: Garrett
authors.forename: Mareike
authors.initials: M
authors.lastname: Kessenbrock
authors.forename: Georg
authors.initials: G
authors.lastname: Groth
authors.forename: Mark L
authors.initials: ML
authors.lastname: Tucker
authors.forename: Bret
authors.initials: B
authors.lastname: Cooper
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Kieber
authors.forename: Caren
authors.initials: C
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism* / Q000494:pharmacology; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D029681:Arabidopsis Proteins; C119963:EIN2 protein, Arabidopsis; D005030:Ethylenes; D010937:Plant Growth Regulators; D011956:Receptors, Cell Surface; D010768:Phosphoserine; C036216:ethylene; D011494:Protein Kinases; C477753:CTR1 protein, Arabidopsis