title: Recognition and activation domains contribute to allele-specific responses of an Arabidopsis NLR receptor to an oomycete effector protein.
abstract: In plants, specific recognition of pathogen effector proteins by nucleotide-binding leucine-rich repeat (NLR) receptors leads to activation of immune responses. RPP1, an NLR from Arabidopsis thaliana, recognizes the effector ATR1, from the oomycete pathogen Hyaloperonospora arabidopsidis, by direct association via C-terminal leucine-rich repeats (LRRs). Two RPP1 alleles, RPP1-NdA and RPP1-WsB, have narrow and broad recognition spectra, respectively, with RPP1-NdA recognizing a subset of the ATR1 variants recognized by RPP1-WsB. In this work, we further characterized direct effector recognition through random mutagenesis of an unrecognized ATR1 allele, ATR1-Cala2, screening for gain-of-recognition phenotypes in a tobacco hypersensitive response assay. We identified ATR1 mutants that a) confirm surface-exposed residues contribute to recognition by RPP1, and b) are recognized by and activate the narrow-spectrum allele RPP1-NdA, but not RPP1-WsB, in co-immunoprecipitation and bacterial growth inhibition assays. Thus, RPP1 alleles have distinct recognition specificities, rather than simply different sensitivity to activation. Using chimeric RPP1 constructs, we showed that RPP1-NdA LRRs were sufficient for allele-specific recognition (association with ATR1), but insufficient for receptor activation in the form of HR. Additional inclusion of the RPP1-NdA ARC2 subdomain, from the central NB-ARC domain, was required for a full range of activation specificity. Thus, cooperation between recognition and activation domains seems to be essential for NLR function.
authors: Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, United States of America.
authors: Adam D
authors: AD
authors: Steinbrenner
authors: Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, United States of America.
authors: Sandra
authors: S
authors: Goritschnig
authors: Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, United States of America.
authors: Brian J
authors: BJ
authors: Staskawicz
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000469:parasitology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D054884:Host-Pathogen Interactions / Q000502:physiology*; D009868:Oomycetes / Q000502:physiology*; D010935:Plant Diseases / Q000235:genetics / Q000469:parasitology*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D011956:Receptors, Cell Surface