title: Interaction of the Arabidopsis GTPase RabA4c with its effector PMR4 results in complete penetration resistance to powdery mildew.
abstract: The (1,3)-β-glucan callose is a major component of cell wall thickenings in response to pathogen attack in plants. GTPases have been suggested to regulate pathogen-induced callose biosynthesis. To elucidate the regulation of callose biosynthesis in Arabidopsis thaliana, we screened microarray data and identified transcriptional upregulation of the GTPase RabA4c after biotic stress. We studied the function of RabA4c in its native and dominant negative (dn) isoform in RabA4c overexpression lines. RabA4c overexpression caused complete penetration resistance to the virulent powdery mildew Golovinomyces cichoracearum due to enhanced callose deposition at early time points of infection, which prevented fungal ingress into epidermal cells. By contrast, RabA4c(dn) overexpression did not increase callose deposition or penetration resistance. A cross of the resistant line with the pmr4 disruption mutant lacking the stress-induced callose synthase PMR4 revealed that enhanced callose deposition and penetration resistance were PMR4-dependent. In live-cell imaging, tagged RabA4c was shown to localize at the plasma membrane prior to infection, which was broken in the pmr4 disruption mutant background, with callose deposits at the site of attempted fungal penetration. Together with our interactions studies including yeast two-hybrid, pull-down, and in planta fluorescence resonance energy transfer assays, we concluded that RabA4c directly interacts with PMR4, which can be seen as an effector of this GTPase.
authors: Phytopathology and Biochemistry, Biocenter Klein Flottbek, University of Hamburg, 22609 Hamburg, Germany.
authors: Dorothea
authors: D
authors: Ellinger
authors: Phytopathology and Biochemistry, Biocenter Klein Flottbek, University of Hamburg, 22609 Hamburg, Germany.
authors: Annemarie
authors: A
authors: Glöckner
authors: Phytopathology and Biochemistry, Biocenter Klein Flottbek, University of Hamburg, 22609 Hamburg, Germany.
authors: Jasmin
authors: J
authors: Koch
authors: Phytopathology and Biochemistry, Biocenter Klein Flottbek, University of Hamburg, 22609 Hamburg, Germany.
authors: Marcel
authors: M
authors: Naumann
authors: Phytopathology and Biochemistry, Biocenter Klein Flottbek, University of Hamburg, 22609 Hamburg, Germany.
authors: Vanessa
authors: V
authors: Stürtz
authors: Phytopathology and Biochemistry, Biocenter Klein Flottbek, University of Hamburg, 22609 Hamburg, Germany.
authors: Kevin
authors: K
authors: Schütt
authors: Phytopathology and Biochemistry, Biocenter Klein Flottbek, University of Hamburg, 22609 Hamburg, Germany.
authors: Chithra
authors: C
authors: Manisseri
authors: Energy Biosciences Institute, University of California, Berkeley, California 94720.
authors: Shauna C
authors: SC
authors: Somerville
authors: Phytopathology and Biochemistry, Biocenter Klein Flottbek, University of Hamburg, 22609 Hamburg, Germany Energy Biosciences Institute, University of California, Berkeley, California 94720 christian.voigt@uni-hamburg.de.
authors: Christian A
authors: CA
authors: Voigt
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology / Q000502:physiology* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001203:Ascomycota / Q000502:physiology; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D005936:Glucans / Q000378:metabolism*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D019441:Plant Epidermis / Q000235:genetics / Q000276:immunology / Q000502:physiology / Q000648:ultrastructure; D057865:Plant Immunity; D018515:Plant Leaves / Q000235:genetics / Q000276:immunology / Q000502:physiology / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D020798:Two-Hybrid System Techniques; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D005936:Glucans; C048306:callose; D005964:Glucosyltransferases; C000599352:PMR4 protein, Arabidopsis; C020570:1,3-beta-glucan synthase; D020558:GTP Phosphohydrolases; C000599351:RabA4c protein, Arabidopsis; D020691:rab GTP-Binding Proteins