title: Arabidopsis heterotrimeric G-protein regulates cell wall defense and resistance to necrotrophic fungi.
abstract: The Arabidopsis heterotrimeric G-protein controls defense responses to necrotrophic and vascular fungi. The agb1 mutant impaired in the Gβ subunit displays enhanced susceptibility to these pathogens. Gβ/AGB1 forms an obligate dimer with either one of the Arabidopsis Gγ subunits (γ1/AGG1 and γ2/AGG2). Accordingly, we now demonstrate that the agg1 agg2 double mutant is as susceptible as agb1 plants to the necrotrophic fungus Plectosphaerella cucumerina. To elucidate the molecular basis of heterotrimeric G-protein-mediated resistance, we performed a comparative transcriptomic analysis of agb1-1 mutant and wild-type plants upon inoculation with P. cucumerina. This analysis, together with metabolomic studies, demonstrated that G-protein-mediated resistance was independent of defensive pathways required for resistance to necrotrophic fungi, such as the salicylic acid, jasmonic acid, ethylene, abscisic acid, and tryptophan-derived metabolites signaling, as these pathways were not impaired in agb1 and agg1 agg2 mutants. Notably, many mis-regulated genes in agb1 plants were related with cell wall functions, which was also the case in agg1 agg2 mutant. Biochemical analyses and Fourier Transform InfraRed (FTIR) spectroscopy of cell walls from G-protein mutants revealed that the xylose content was lower in agb1 and agg1 agg2 mutants than in wild-type plants, and that mutant walls had similar FTIR spectratypes, which differed from that of wild-type plants. The data presented here suggest a canonical functionality of the Gβ and Gγ1/γ2 subunits in the control of Arabidopsis immune responses and the regulation of cell wall composition.
authors: Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Campus de Montegancedo, E-28223-Pozuelo de Alarcón (Madrid), Spain.
authors: Magdalena
authors: M
authors: Delgado-Cerezo
authors: Clara
authors: C
authors: Sánchez-Rodríguez
authors: Viviana
authors: V
authors: Escudero
authors: Eva
authors: E
authors: Miedes
authors: Paula Virginia
authors: PV
authors: Fernández
authors: Lucía
authors: L
authors: Jordá
authors: Camilo
authors: C
authors: Hernández-Blanco
authors: Andrea
authors: A
authors: Sánchez-Vallet
authors: Pawel
authors: P
authors: Bednarek
authors: Paul
authors: P
authors: Schulze-Lefert
authors: Shauna
authors: S
authors: Somerville
authors: José Manuel
authors: JM
authors: Estevez
authors: Staffan
authors: S
authors: Persson
authors: Antonio
authors: A
authors: Molina
mesh_terms: D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000276:immunology*; D001203:Ascomycota / Q000276:immunology / Q000502:physiology*; D002473:Cell Wall / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D019281:Dimerization; D060467:Disease Resistance; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000276:immunology*; D044388:GTP-Binding Protein gamma Subunits / Q000235:genetics / Q000276:immunology*; D018506:Gene Expression Regulation, Plant; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*
chemical_list: C089590:AGB1 protein, Arabidopsis; C521249:AGG1 protein, Arabidopsis; C521250:AGG2 protein, Arabidopsis; D029681:Arabidopsis Proteins; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits