Department of Crop and Soil Sciences, Veterinary Microbiology and Pathology, and Plant Pathology, Washington State University, Pullman, WA 99164, USA.
Proc Natl Acad Sci U S A. 2011 Aug 30;108(35):14676-81. doi: 10.1073/pnas.1111771108. Epub 2011 Aug 22.
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.
大麦抗条锈病基因 Reaction to Puccinia graminis 1 (Rpg1)，编码一种受体样激酶，赋予其对小麦条锈病菌 Puccinia graminis f. sp. tritici 的持久抗性。真菌的夏孢子在接种后 1 小时内与叶片表皮细胞形成附着结构，随后形成菌丝和吸器。RPG1 蛋白持续表达且不磷酸化。接种无毒夏孢子时，它在体内 5 分钟内被磷酸化，随后被降解。精氨酸-甘氨酸-天冬氨酸肽环的应用阻止了附着孢子的附着结构的形成、RPG1 的磷酸化和有活力孢子的萌发。从未萌发的无毒锈孢子中蛋白质的精氨酸-甘氨酸-天冬氨酸亲和层析导致了一种具有纤连蛋白 III 和乳腺癌 1 易感性蛋白结构域的蛋白质和一种与内质网降解域连接的泛素的液泡蛋白分选相关蛋白 9 的纯化和鉴定。这两种蛋白质都需要诱导 RPG1 的体内磷酸化和降解。两种蛋白质的联合应用导致在抗条锈病品种 Morex 上引发过敏反应，但在易感品种 Steptoe 上则不会。表达研究表明，两种基因的 mRNA 存在于未萌发的夏孢子中，并在孢子体、感染的叶片和调查的无毒菌系中的吸器中持续转录。有证据表明，在酵母中，RPG1 与来自夏孢子的两种蛋白效应子相互作用，在吸器形成之前很长时间就协同激活条锈病抗性蛋白 RPG1。
