title: Interaction of a Blumeria graminis f. sp. hordei effector candidate with a barley ARF-GAP suggests that host vesicle trafficking is a fungal pathogenicity target.
abstract: Filamentous phytopathogens, such as fungi and oomycetes, secrete effector proteins to establish successful interactions with their plant hosts. In contrast with oomycetes, little is known about effector functions in true fungi. We used a bioinformatics pipeline to identify Blumeria effector candidates (BECs) from the obligate biotrophic barley powdery mildew pathogen, Blumeria graminis f. sp. hordei (Bgh). BEC1-BEC5 are expressed at different time points during barley infection. BEC1, BEC2 and BEC4 have orthologues in the Arabidopsis thaliana-infecting powdery mildew fungus Golovinomyces orontii. Arabidopsis lines stably expressing the G. orontii BEC2 orthologue, GoEC2, are more susceptible to infection with the non-adapted fungus Erysiphe pisi, suggesting that GoEC2 contributes to powdery mildew virulence. For BEC3 and BEC4, we identified thiopurine methyltransferase, a ubiquitin-conjugating enzyme, and an ADP ribosylation factor-GTPase-activating protein (ARF-GAP) as potential host targets. Arabidopsis knockout lines of the respective HvARF-GAP orthologue (AtAGD5) allowed higher entry levels of E. pisi, but exhibited elevated resistance to the oomycete Hyaloperonospora arabidopsidis. We hypothesize that ARF-GAP proteins are conserved targets of powdery and downy mildew effectors, and we speculate that BEC4 might interfere with defence-associated host vesicle trafficking.
authors.affiliation: Department of Plant-Microbe Interactions, Max-Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, D-50829, Köln, Germany.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Schmidt
authors.forename: Hannah
authors.initials: H
authors.lastname: Kuhn
authors.forename: Cristina
authors.initials: C
authors.lastname: Micali
authors.forename: Corinna
authors.initials: C
authors.lastname: Liller
authors.forename: Mark
authors.initials: M
authors.lastname: Kwaaitaal
authors.forename: Ralph
authors.initials: R
authors.lastname: Panstruga
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D001203:Ascomycota / Q000235:genetics* / Q000472:pathogenicity*; D019295:Computational Biology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D017343:Genes, Plant; D001467:Hordeum / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology*; D054884:Host-Pathogen Interactions / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D025941:Protein Interaction Mapping; D017386:Sequence Homology, Amino Acid; D014774:Virulence / Q000235:genetics
chemical_list: D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D010940:Plant Proteins
keywords: ARF-GAP; Blumeria graminis f. sp. hordei; Erysiphe pisi; Golovinomyces orontii; effector; powdery mildew; vesicle trafficking