title: Mitogen-activated protein kinase pathways are required for melatonin-mediated defense responses in plants.
abstract: Melatonin enhances pathogen resistance by inducing the expression of a number of plant defense-related genes. To examine whether the melatonin-mediated pathogen resistance is associated with mitogen-activated protein kinase (MAPK) cascades, Arabidopsis and tobacco leaves were treated with melatonin and investigated for MAPK activation using an antiphospho-p44/42 MAPK (Erk1/2) monoclonal antibody. Two MAPKs, MPK3 and MPK6, were activated rapidly and transiently by 1 μm melatonin treatment in Arabidopsis. Its tobacco ortholog MAPKs were also activated. The activation of MPK3 and MPK6 by 2-hydroxymelatonin and N-acetylserotonin was also observed, albeit to a lesser degree than that by melatonin. Furthermore, MAPK activation by melatonin was uncoupled from G-protein signaling, because melatonin efficiently activated two MAPKs in a G-protein β knockout mutant (agb1). Suppression of both MPK3 and MPK6 in transgenic Arabidopsis exhibited significant decreases in the induction of defense-related gene expression and pathogen resistance relative to wild-type plants. Using an array of MAP kinase kinase (MKK) knockout mutants, we found that four MKKs, namely MKK4, MKK5, MKK7, and MKK9, are responsible for the activation of MPK3 and MPK6 by melatonin, indicating that melatonin-mediated innate immunity is triggered by MAPK signaling through MKK4/5/7/9-MPK3/6 cascades.
authors.affiliation: Department of Biotechnology, Bioenergy Research Center, Chonnam National University, Gwangju, Korea.
authors.forename: Hyoung Yool
authors.initials: HY
authors.lastname: Lee
authors.affiliation: Department of Biotechnology, Bioenergy Research Center, Chonnam National University, Gwangju, Korea.
authors.forename: Kyoungwhan
authors.initials: K
authors.lastname: Back
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000276:immunology*; D060467:Disease Resistance / Q000502:physiology*; D004789:Enzyme Activation / Q000235:genetics / Q000276:immunology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000276:immunology*; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000276:immunology*; D055785:Gene Knockdown Techniques; D020935:MAP Kinase Signaling System / Q000235:genetics / Q000276:immunology*; D008550:Melatonin / Q000235:genetics / Q000276:immunology*; D014026:Nicotiana / Q000235:genetics / Q000276:immunology
chemical_list: C089590:AGB1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D044387:GTP-Binding Protein beta Subunits; D048049:Extracellular Signal-Regulated MAP Kinases; D008550:Melatonin
keywords: Arabidopsis thaliana; MAP kinase kinase; MPK3; MPK6; pathogen resistance