title: The role of Arabidopsis heterotrimeric G-protein subunits in MLO2 function and MAMP-triggered immunity.
abstract: Heterotrimeric G-proteins, composed of Gα, Gβ, and Gγ subunits, regulate many fundamental processes in plants. In animals, ligand binding to seven transmembrane (7TM) cell surface receptors designated G-protein coupled receptors (GPCR) leads to heterotrimeric G-protein activation. Because the plant G-protein complex is constitutively active, the exact role of plant 7TM proteins in this process is unclear. Members of the mildew resistance locus O (MLO) family represent the best-characterized 7TM plant proteins. Although genetic ablation of either MLO2 or G-proteins alters susceptibility to pathogens in Arabidopsis thaliana, it is unknown whether G-proteins directly couple signaling through MLO2. Here, we exploited two well-documented phenotypes of mlo2 mutants, broad-spectrum powdery mildew resistance and spontaneous callose deposition in leaf mesophyll cells, to assess the relationship of MLO2 proteins to the G-protein complex. Although our data reveal modulation of antifungal defense responses by Gβ and Gγ subunits and a role for the Gγ1 subunit in mlo2-conditioned callose deposition, our findings overall are inconsistent with a role of MLO2 as a canonical GPCR. We discovered that mutants lacking the Gβ subunit show delayed accumulation of a subset of defense-associated genes following exposure to the microbe-associated molecular pattern flg22. Moreover, Gβ mutants were found to be hypersusceptible to spray inoculation with the bacterial pathogen Pseudomonas syringae.
authors: Max Planck Institute for Plant Breeding Research, Köln, Germany.
authors: Justine
authors: J
authors: Lorek
authors: Thomas
authors: T
authors: Griebel
authors: Alan M
authors: AM
authors: Jones
authors: Hannah
authors: H
authors: Kuhn
authors: Ralph
authors: R
authors: Panstruga
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000382:microbiology / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001203:Ascomycota / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D060467:Disease Resistance; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005936:Glucans / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D058503:Mesophyll Cells; D008954:Models, Biological; D009154:Mutation; D010641:Phenotype; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D030821:Plants, Genetically Modified; D021122:Protein Subunits; D044224:Pseudomonas syringae / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000166:cytology / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D015398:Signal Transduction
chemical_list: C089590:AGB1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D044387:GTP-Binding Protein beta Subunits; D005936:Glucans; C573497:MLO2 protein, Arabidopsis; D008565:Membrane Proteins; D021122:Protein Subunits; D017382:Reactive Oxygen Species; C048306:callose; D020962:Heterotrimeric GTP-Binding Proteins
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