Abstract:Stem rust threatens cereal production worldwide. Understanding the mechanism by which durable resistance genes, such as Rpg1, function is critical. We show that the RPG1 protein is phosphorylated within 5 min by exposure to spores from avirulent but not virulent races of stem rust. Transgenic mutants encoding an RPG1 protein with an in vitro inactive kinase domain fail to phosphorylate RPG1 in vivo and are susceptible to stem rust, demonstrating that phosphorylation is a prerequisite for disease resistance. Pr… Show more
“…Seedlings were grown in a growth chambers at 24°C and 80% relative humidity for 1 wk before inoculation. Plants were inoculated with the rust fungus (at a rate of 0.025 mg of spores per plant) as previously described (40). Tissue samples were collected as indicated in the figures.…”
Section: Methodsmentioning
confidence: 99%
“…The urediniospores were rehydrated in a Petri dish for 4 h at room temperature and applied onto the leaves. The plants were sampled 15 and 30 min after application and assayed for RPG1 phosphorylation as previously described (40).…”
Section: Methodsmentioning
confidence: 99%
“…Rpg1 is constitutively expressed (39) and is mostly cytoplasmic, with a small fraction associated with the plasma membrane (38). On inoculation with stem rust urediniospores, RPG1 is phosphorylated in vivo within 5 min (40) and is subsequently degraded (41). Both actions are required for resistance.…”
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.
“…Seedlings were grown in a growth chambers at 24°C and 80% relative humidity for 1 wk before inoculation. Plants were inoculated with the rust fungus (at a rate of 0.025 mg of spores per plant) as previously described (40). Tissue samples were collected as indicated in the figures.…”
Section: Methodsmentioning
confidence: 99%
“…The urediniospores were rehydrated in a Petri dish for 4 h at room temperature and applied onto the leaves. The plants were sampled 15 and 30 min after application and assayed for RPG1 phosphorylation as previously described (40).…”
Section: Methodsmentioning
confidence: 99%
“…Rpg1 is constitutively expressed (39) and is mostly cytoplasmic, with a small fraction associated with the plasma membrane (38). On inoculation with stem rust urediniospores, RPG1 is phosphorylated in vivo within 5 min (40) and is subsequently degraded (41). Both actions are required for resistance.…”
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.
“…Both kinases of RPG1 carry the non-RD motif and are required for disease resistance, yet only protein kinase 2 has catalytic activity in vitro (152). RPG1 localizes to the plasma membrane and cytosol, where it is phosphorylated within minutes after urediniospore attachment to the leaf surface (154). Phosphorylation is required for RPG1 protein degradation via the proteasome pathway after pathogen perception, and both kinases are required for disease resistance (153,154).…”
Section: Innate Immunity Mediated By the Cytoplasmic Non-rd Kinases Rmentioning
Plants and animals sense conserved microbial signatures through receptors localized to the plasma membrane and cytoplasm. These receptors typically carry or associate with non-arginine-aspartate (non-RD) kinases that initiate complex signaling networks cumulating in robust defense responses. In plants, coregulatory receptor kinases have been identified that not only are critical for the innate immune response but also serve an essential function in other regulatory signaling pathways.
“…The reciprocal responses of barley and stem rust belong to ETI of plant. Based on these observations, it is speculated that there would be a unique mechanism for pathogen recognition and signalling in barley that we do not know yet [5,63,64]. Figure 2.The flow chart of the interaction between stem rust fungus and barley.…”
Section: Plant Disease Resistance Genes Involved In the Early Responsementioning
Plants can be infected by a variety of pathogens, most of which can cause severe economic losses. The plants resist the invasion of pathogens via the innate or acquired immune system for surviving biotic stress. The associations between plants and pathogens are sophisticated beyond imaging and the interactions between them can occur at a very early stage after their touching each other. A number of researchers in the past decade have shown that many biochemical events appeared even as early as 5 min after their touching for plant disease resistance response. The early molecular interactions of plants and pathogens are likely to involve protein phosphorylation, ion fluxes, reactive oxygen species (ROS) and other signalling transduction. Here, we reviewed the recent progress in the study for molecular interaction response of fungal pathogens and host plant at the early infection stage, which included many economically important crop fungal pathogens such as cereal rust fungi, tomato Cladosporium fulvum, rice blast and so on. By dissecting the earlier infection stage of the diseases, the avirulent/virulent genes of pathogen or resistance genes of plant could be defined more clearly and accurately, which would undoubtedly facilitate fungal pathogenesis study and resistant crop breeding.
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