title: Apoplastic recognition of multiple candidate effectors from the wheat pathogen Zymoseptoria tritici in the nonhost plant Nicotiana benthamiana.
abstract: The fungus Zymoseptoria tritici is a strictly apoplastic, host-specific pathogen of wheat leaves and causal agent of septoria tritici blotch (STB) disease. All other plants are considered nonhosts, but the mechanism of nonhost resistance (NHR) to Z. tritici has not been addressed previously. We sought to develop Nicotiana benthamiana as a system to study NHR against Z. tritici. Fluorescence microscopy and quantitative reverse transcription polymerase chain reactions were used to establish the interaction between Z. tritici and N. benthamiana. Agrobacterium-mediated transient expression was used to screen putative Z. tritici effector genes for recognition in N. benthamiana, and virus-induced gene silencing (VIGS) was employed to determine the role of two receptor-like kinases (RLKs), NbBAK1 and NbSOBIR1, in Z. tritici effector recognition. Numerous Z. tritici putative effectors (14 of 63 tested) induced cell death or chlorosis in N. benthamiana. For most, phenotypes were light-dependent and required effector secretion to the leaf apoplastic space. Moreover, effector-induced host cell death was dependent on NbBAK1 and NbSOBIR1. Our results indicate widespread recognition of apoplastic effectors from a wheat-infecting fungal pathogen in a taxonomically distant nonhost plant species presumably by cell surface immune receptors. This suggests that apoplastic recognition of multiple nonadapted pathogen effectors may contribute to NHR.
authors.affiliation: Department of Plant Biology & Crop Science, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors.forename: Graeme J
authors.initials: GJ
authors.lastname: Kettles
authors.affiliation: Department of Plant Biology & Crop Science, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors.forename: Carlos
authors.initials: C
authors.lastname: Bayon
authors.affiliation: Department of Plant Biology & Crop Science, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors.forename: Gail
authors.initials: G
authors.lastname: Canning
authors.affiliation: Department of Plant Biology & Crop Science, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Rudd
authors.affiliation: Department of Plant Biology & Crop Science, Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors.forename: Kostya
authors.identifier: 0000-0001-6324-4123
authors.initials: K
authors.lastname: Kanyuka
mesh_terms: D060054:Agrobacterium / Q000378:metabolism; D001203:Ascomycota / Q000166:cytology / Q000502:physiology*; D016923:Cell Death; D005656:Fungal Proteins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D008027:Light; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D014026:Nicotiana / Q000382:microbiology*; D014158:Transcription, Genetic; D014908:Triticum / Q000382:microbiology*
chemical_list: D005656:Fungal Proteins
keywords: 
  Mycosphaerella graminicola
  ; 
  Septoria tritici
  ; 
  Zymoseptoria tritici
  ; Nicotiana benthamiana (tobacco); effector; nonhost resistance (NHR); receptor-like kinase (RLK); virus-induced gene silencing (VIGS)