The University of Sydney, Faculty of Science, Plant Breeding Institute, Cobbitty, NSW, 2570, Australia.
The Sainsbury Laboratory, University of East Anglia, Norwich Research Park, Norwich, NR4 7UK, UK.
Nat Commun. 2022 May 2;13(1):2386. doi: 10.1038/s41467-022-29840-1.
Leaf rust, caused by Puccinia hordei, is an economically significant disease of barley, but only a few major resistance genes to P. hordei (Rph) have been cloned. In this study, gene Rph3 was isolated by positional cloning and confirmed by mutational analysis and transgenic complementation. The Rph3 gene, which originated from wild barley and was first introgressed into cultivated Egyptian germplasm, encodes a unique predicted transmembrane resistance protein that differs from all known plant disease resistance proteins at the amino acid sequence level. Genetic profiles of diverse accessions indicated limited genetic diversity in Rph3 in domesticated germplasm, and higher diversity in wild barley from the Eastern Mediterranean region. The Rph3 gene was expressed only in interactions with Rph3-avirulent P. hordei isolates, a phenomenon also observed for transcription activator-like effector-dependent genes known as executors conferring resistance to Xanthomonas spp. Like known transmembrane executors such as Bs3 and Xa7, heterologous expression of Rph3 in N. benthamiana induced a cell death response. The isolation of Rph3 highlights convergent evolutionary processes in diverse plant-pathogen interaction systems, where similar defence mechanisms evolved independently in monocots and dicots.
叶锈病由禾柄锈菌引起，是大麦的一种重要经济病害，但仅有少数几个主要的抗禾柄锈菌基因（Rph）被克隆。本研究通过定位克隆分离了基因 Rph3，并通过突变分析和转基因互补进行了验证。Rph3 基因源自野生大麦，最初被导入栽培的埃及种质中，它编码一种独特的预测跨膜抗性蛋白，在氨基酸序列水平上与所有已知的植物抗病蛋白不同。不同品种的遗传图谱表明，驯化种质中 Rph3 的遗传多样性有限，而来自东地中海地区的野生大麦的多样性较高。Rph3 基因仅在与 Rph3-无毒禾柄锈菌分离物的相互作用中表达，这一现象也见于已知的转录激活因子样效应物依赖性基因，即执行者，它们赋予对黄单胞菌属的抗性。与已知的跨膜执行者如 Bs3 和 Xa7 一样，Rph3 在 N. benthamiana 中的异源表达诱导了细胞死亡反应。Rph3 的分离突出了不同植物-病原体相互作用系统中趋同进化过程，在单子叶植物和双子叶植物中独立进化出了类似的防御机制。
