title: Subcellular localization of the Hpa RxLR effector repertoire identifies a tonoplast-associated protein HaRxL17 that confers enhanced plant susceptibility.
abstract: Filamentous phytopathogens form sophisticated intracellular feeding structures called haustoria in plant cells. Pathogen effectors are likely to play a role in the establishment and maintenance of haustoria in addition to their better-characterized role in suppressing plant defence. However, the specific mechanisms by which these effectors promote virulence remain unclear. To address this question, we examined changes in subcellular architecture using live-cell imaging during the compatible interaction between the oomycete Hyaloperonospora arabidopsidis (Hpa) and its host Arabidopsis. We monitored host-cell restructuring of subcellular compartments within plant mesophyll cells during haustoria ontogenesis. Live-cell imaging highlighted rearrangements in plant cell membranes upon infection, in particular to the tonoplast, which was located close to the extra-haustorial membrane surrounding the haustorium. We also investigated the subcellular localization patterns of Hpa RxLR effector candidates (HaRxLs) in planta. We identified two major classes of HaRxL effector based on localization: nuclear-localized effectors and membrane-localized effectors. Further, we identified a single effector, HaRxL17, that associated with the tonoplast in uninfected cells and with membranes around haustoria, probably the extra-haustorial membrane, in infected cells. Functional analysis of selected effector candidates in planta revealed that HaRxL17 enhances plant susceptibility. The roles of subcellular changes and effector localization, with specific reference to the potential role of HaRxL17 in plant cell membrane trafficking, are discussed with respect to Hpa virulence.
authors.affiliation: The Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Marie-Cécile
authors.initials: MC
authors.lastname: Caillaud
authors.forename: Sophie J M
authors.initials: SJ
authors.lastname: Piquerez
authors.forename: Georgina
authors.initials: G
authors.lastname: Fabro
authors.forename: Jens
authors.initials: J
authors.lastname: Steinbrenner
authors.forename: Naveed
authors.initials: N
authors.lastname: Ishaque
authors.forename: Jim
authors.initials: J
authors.lastname: Beynon
authors.forename: Jonathan D G
authors.initials: JD
authors.lastname: Jones
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000276:immunology* / Q000469:parasitology / Q000502:physiology / Q000648:ultrastructure; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D054884:Host-Pathogen Interactions / Q000276:immunology* / Q000502:physiology; D058503:Mesophyll Cells / Q000378:metabolism; D008969:Molecular Sequence Data; D009868:Oomycetes / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity*; D010935:Plant Diseases / Q000276:immunology* / Q000469:parasitology; D057865:Plant Immunity / Q000276:immunology*; D030821:Plants, Genetically Modified; D011110:Polymorphism, Genetic / Q000235:genetics; D021381:Protein Transport; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000276:immunology / Q000469:parasitology / Q000502:physiology / Q000648:ultrastructure; D016415:Sequence Alignment; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D014617:Vacuoles / Q000378:metabolism; D014774:Virulence
chemical_list: D011506:Proteins