title: A role in immunity for Arabidopsis cysteine protease RD21, the ortholog of the tomato immune protease C14.
abstract: Secreted papain-like Cys proteases are important players in plant immunity. We previously reported that the C14 protease of tomato is targeted by cystatin-like EPIC proteins that are secreted by the oomycete pathogen Phytophthora infestans (Pinf) during infection. C14 has been under diversifying selection in wild potato species coevolving with Pinf and reduced C14 levels result in enhanced susceptibility for Pinf. Here, we investigated the role C14-EPIC-like interactions in the natural pathosystem of Arabidopsis with the oomycete pathogen Hyaloperonospora arabidopsidis (Hpa). In contrast to the Pinf-solanaceae pathosystem, the C14 orthologous protease of Arabidopsis, RD21, does not evolve under diversifying selection in Arabidopsis, and rd21 null mutants do not show phenotypes upon compatible and incompatible Hpa interactions, despite the evident lack of a major leaf protease. Hpa isolates express highly conserved EPIC-like proteins during infections, but it is unknown if these HpaEPICs can inhibit RD21 and one of these HpaEPICs even lacks the canonical cystatin motifs. The rd21 mutants are unaffected in compatible and incompatible interactions with Pseudomonas syringae pv. tomato, but are significantly more susceptible for the necrotrophic fungal pathogen Botrytis cinerea, demonstrating that RD21 provides immunity to a necrotrophic pathogen.
authors.affiliation: The Plant Chemetics Laboratory, Chemical Genomics Centre of the Max Planck Society and Max Planck Institute for Plant Breeding Research, Cologne, Germany.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Shindo
authors.forename: Johana C
authors.initials: JC
authors.lastname: Misas-Villamil
authors.forename: Anja C
authors.initials: AC
authors.lastname: Hörger
authors.forename: Jing
authors.initials: J
authors.lastname: Song
authors.forename: Renier A L
authors.initials: RA
authors.lastname: van der Hoorn
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000276:immunology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D020171:Botrytis / Q000276:immunology / Q000502:physiology; D057056:Cysteine Proteases / Q000235:genetics / Q000502:physiology*; D007113:Immunity, Innate / Q000235:genetics*; D018551:Solanum lycopersicum / Q000235:genetics* / Q000276:immunology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D044224:Pseudomonas syringae / Q000276:immunology; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D057056:Cysteine Proteases; C549570:RD21 protein, Arabidopsis