Pea powdery mildew (PM) is an important fungal disease caused by an obligate biotroph, Erysiphe pisi (Ep), which significantly impacts pea production worldwide. The phytopathogen secretes a plethora of effectors, primarily through specialized infection structures termed haustoria, to establish a dynamic relationship with its host. To identify Ep effector candidates, a cDNA library of enriched haustoria from Ep‐infected pea leaves was sequenced. The Ep transcriptome encodes 622 Ep candidate secreted proteins (CSPs), of which 167 were predicted to be candidate secreted effector proteins (CSEPs). Phylogenetic analysis indicates that Ep CSEPs are highly diverse, but, unlike cereal PM CSEPs, exhibit extensive sequence similarity with effectors from other PMs. Quantitative real‐time PCR of a subset of EpCSEP/CSPs revealed that the majority are preferentially expressed in haustoria and exhibit infection stage–specific expression patterns. The functional roles of EpCSEP001, EpCSEP009 and EpCSP083 were probed by host‐induced gene silencing (HIGS) via a double‐stranded (ds) RNA‐mediated RNAi approach. Foliar application of individual EpCSEP/CSP dsRNAs resulted in a marked reduction in PM disease symptoms. These findings were consistent with microscopic and molecular studies, suggesting that these Ep CSEP/CSPs play important roles in pea PM pathogenesis. Homology modelling revealed that EpCSEP001 and EpCSEP009 are analogous to fungal ribonucleases and belong to the RALPH family of effectors. This is the first study to identify and functionally validate candidate effectors from the agriculturally relevant pea PM, and highlights the utility of transcriptomics and HIGS to elucidate the key proteins associated with Ep pathogenesis.

中文翻译：

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从白粉菌吸器转录组中挖掘效应子，鉴定出参与豌豆白粉病发病机制的新候选者。


豌豆白粉病 (PM) 是一种重要的真菌病害，由专性生物营养型白粉菌( Ep ) 引起，严重影响全球豌豆生产。植物病原体主要通过称为吸器的特殊感染结构分泌大量效应子，以与其宿主建立动态关系。为了鉴定Ep效应子候选者，对来自Ep感染的豌豆叶子的富集吸器的 cDNA 文库进行了测序。 Ep转录组编码622个Ep候选分泌蛋白（CSP），其中167个被预测为候选分泌效应蛋白（CSEP）。系统发育分析表明Ep CSEP 高度多样化，但与谷物 PM CSEP 不同，Ep CSEP 与其他 PM 的效应子表现出广泛的序列相似性。对EpCSEP / CSP子集的定量实时 PCR 显示，大多数优先在吸器中表达，并表现出感染阶段特异性的表达模式。 EpCSEP001 、 EpCSEP009和EpCSP083的功能作用通过宿主诱导基因沉默 (HIGS) 通过双链 (ds) RNA 介导的 RNAi 方法进行探测。叶面喷施单独的EpCSEP / CSP dsRNA 可显着减少 PM 疾病症状。这些发现与微观和分子研究一致，表明这些Ep CSEP/CSP 在豌豆 PM 发病机制中发挥重要作用。同源建模显示Ep CSEP001 和Ep CSEP009 与真菌核糖核酸酶类似，属于 RALPH 效应子家族。 这是第一项从农业相关的豌豆 PM 中识别和功能验证候选效应子的研究，并强调了转录组学和 HIGS 在阐明与Ep发病机制相关的关键蛋白质方面的效用。