title: Concerted action of two avirulent spore effectors activates Reaction to Puccinia graminis 1 (Rpg1)-mediated cereal stem rust resistance.
abstract: The barley stem rust resistance gene Reaction to Puccinia graminis 1 (Rpg1), encoding a receptor-like kinase, confers durable resistance to the stem rust pathogen Puccinia graminis f. sp. tritici. The fungal urediniospores form adhesion structures with the leaf epidermal cells within 1 h of inoculation, followed by hyphae and haustorium formation. The RPG1 protein is constitutively expressed and not phosphorylated. On inoculation with avirulent urediniospores, it is phosphorylated in vivo within 5 min and subsequently degraded. Application of arginine-glycine-aspartic acid peptide loops prevented the formation of adhesion structures for spore attachment, the phosphorylation of RPG1, and germination of the viable spores. Arginine-glycine-aspartic acid affinity chromatography of proteins from the ungerminated avirulent rust spores led to the purification and identification of a protein with fibronectin type III and breast cancer type 1 susceptibility protein domains and a vacuolar protein sorting-associated protein 9 with a coupling of ubiquitin to endoplasmic reticulum degradation domain. Both proteins are required to induce in vivo phosphorylation and degradation of RPG1. Combined application of both proteins caused hypersensitive reaction on the stem rust-resistant cultivar Morex but not on the susceptible cultivar Steptoe. Expression studies indicated that mRNA of both genes are present in ungerminated urediniospores and are constitutively transcribed in sporelings, infected leaves, and haustoria in the investigated avirulent races. Evidence is presented that RPG1, in yeast, interacts with the two protein effectors from the urediniospores that activate cooperatively the stem rust resistance protein RPG1 long before haustoria formation.
authors.affiliation: Department of Crop and Soil Sciences, Veterinary Microbiology and Pathology, and Plant Pathology, Washington State University, Pullman, WA 99164, USA.
authors.forename: Jayaveeramuthu
authors.initials: J
authors.lastname: Nirmala
authors.forename: Tom
authors.initials: T
authors.lastname: Drader
authors.forename: Paulraj K
authors.initials: PK
authors.lastname: Lawrence
authors.forename: Chuntao
authors.initials: C
authors.lastname: Yin
authors.forename: Scot
authors.initials: S
authors.lastname: Hulbert
authors.forename: Camille M
authors.initials: CM
authors.lastname: Steber
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Steffenson
authors.forename: Les J
authors.initials: LJ
authors.lastname: Szabo
authors.forename: Diter
authors.initials: D
authors.lastname: von Wettstein
authors.forename: Andris
authors.initials: A
authors.lastname: Kleinhofs
mesh_terms: D001483:Base Sequence; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000502:physiology; D001467:Hordeum / Q000201:enzymology / Q000235:genetics*; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism; D010766:Phosphorylation; D010935:Plant Diseases / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D018547:Plant Stems; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000502:physiology
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D009842:Oligopeptides; D010940:Plant Proteins; D029701:Saccharomyces cerevisiae Proteins; C099285:VPS9 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C047981:arginyl-glycyl-aspartic acid; D017346:Protein Serine-Threonine Kinases