title: Cytosolic activation of cell death and stem rust resistance by cereal MLA-family CC-NLR proteins.
abstract: Plants possess intracellular immune receptors designated "nucleotide-binding domain and leucine-rich repeat" (NLR) proteins that translate pathogen-specific recognition into disease-resistance signaling. The wheat immune receptors Sr33 and Sr50 belong to the class of coiled-coil (CC) NLRs. They confer resistance against a broad spectrum of field isolates of Puccinia graminis f. sp. tritici, including the Ug99 lineage, and are homologs of the barley powdery mildew-resistance protein MLA10. Here, we show that, similarly to MLA10, the Sr33 and Sr50 CC domains are sufficient to induce cell death in Nicotiana benthamiana Autoactive CC domains and full-length Sr33 and Sr50 proteins self-associate in planta In contrast, truncated CC domains equivalent in size to an MLA10 fragment for which a crystal structure was previously determined fail to induce cell death and do not self-associate. Mutations in the truncated region also abolish self-association and cell-death signaling. Analysis of Sr33 and Sr50 CC domains fused to YFP and either nuclear localization or nuclear export signals in N benthamiana showed that cell-death induction occurs in the cytosol. In stable transgenic wheat plants, full-length Sr33 proteins targeted to the cytosol provided rust resistance, whereas nuclear-targeted Sr33 was not functional. These data are consistent with CC-mediated induction of both cell-death signaling and stem rust resistance in the cytosolic compartment, whereas previous research had suggested that MLA10-mediated cell-death and disease resistance signaling occur independently, in the cytosol and nucleus, respectively.
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Agriculture, Canberra, ACT 2601, Australia;
authors.forename: Stella
authors.initials: S
authors.lastname: Cesari
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Agriculture, Canberra, ACT 2601, Australia;
authors.forename: John
authors.initials: J
authors.lastname: Moore
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Agriculture, Canberra, ACT 2601, Australia;
authors.forename: Chunhong
authors.initials: C
authors.lastname: Chen
authors.affiliation: Centre for Advanced Microscopy, Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Daryl
authors.initials: D
authors.lastname: Webb
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Agriculture, Canberra, ACT 2601, Australia;
authors.forename: Sambasivam
authors.initials: S
authors.lastname: Periyannan
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Agriculture, Canberra, ACT 2601, Australia;
authors.forename: Rohit
authors.initials: R
authors.lastname: Mago
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Agriculture, Canberra, ACT 2601, Australia;
authors.forename: Maud
authors.initials: M
authors.lastname: Bernoux
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Agriculture, Canberra, ACT 2601, Australia;
authors.forename: Evans S
authors.initials: ES
authors.lastname: Lagudah
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Agriculture, Canberra, ACT 2601, Australia; peter.dodds@csiro.au.
authors.forename: Peter N
authors.initials: PN
authors.lastname: Dodds
mesh_terms: D000595:Amino Acid Sequence; D001487:Basidiomycota / Q000472:pathogenicity / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism / Q000382:microbiology; D003600:Cytosol / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D060467:Disease Resistance / Q000235:genetics*; D002523:Edible Grain / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D018506:Gene Expression Regulation, Plant; D059828:Plant Cells / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology*; D018547:Plant Stems / Q000235:genetics / Q000276:immunology* / Q000382:microbiology; D030821:Plants, Genetically Modified; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D014908:Triticum / Q000235:genetics / Q000276:immunology* / Q000382:microbiology
chemical_list: D010940:Plant Proteins
keywords: cell death; plant immunity; resistance protein; signaling; wheat stem rust