Cowpea (Vigna unguiculata) cultivar B301 is resistant to races SG4 and SG3 of the root parasitic weed Striga gesnerioides, developing a hypersensitive response (HR) at the site of parasite attachment. By contrast, race SG4z overcomes B301 resistance and successfully parasitises the plant. Comparative transcriptomics and in silico analysis identified a small secreted effector protein dubbed Suppressor of Host Resistance 4z (SHR4z) in the SG4z haustorium that upon transfer to the host roots causes a loss of host immunity (i.e. decreased HR and increased parasite growth). SHR4z has significant homology to the short leucine-rich repeat (LRR) domain of SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) family proteins and functions by binding to VuPOB1, a host BTB-BACK domain-containing ubiquitin E3 ligase homologue, leading to its rapid turnover. VuPOB1 is shown to be a positive regulator of HR since silencing of VuPOB1 expression in transgenic B301 roots lowers the frequency of HR and increases the levels of successful SG4 parasitism and overexpression decreases parasitism by SG4z. These findings provide new insights into how parasitic weeds overcome host defences and could potentially contribute to the development of novel strategies for controlling Striga and other parasitic weeds thereby enhancing crop productivity and food security globally.

中文翻译：

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SHR4z 是一种来自寄生杂草苦苣苔吸器的新型诱饵效应子，可抑制宿主植物的免疫力。

豇豆 (Vigna unguiculata) 品种 B301 对根部寄生杂草 Striga gesnerioides 的 SG4 和 SG3 品种具有抗性，在寄生虫附着部位产生过敏反应 (HR)。相比之下，SG4z 种族克服了 B301 抗性并成功寄生在植物上。比较转录组学和计算机分析在 SG4z 吸器中发现了一种名为宿主抗性 4z 抑制器 (SHR4z) 的小型分泌效应蛋白，一旦转移到宿主根部，就会导致宿主免疫力丧失（即 HR 降低和寄生虫生长增加）。SHR4z 与体细胞胚胎发生受体样激酶 (SERK) 家族蛋白的短亮氨酸重复序列 (LRR) 结构域具有显着的同源性，并通过与 VuPOB1（一种包含宿主 BTB-BACK 结构域的泛素 E3 连接酶同源物）结合发挥功能，从而导致其周转快。VuPOB1 被证明是 HR 的正调节因子，因为转基因 B301 根中 VuPOB1 表达的沉默会降低 HR 的频率，并增加成功 SG4 寄生的水平，而过度表达会减少 SG4z 的寄生。这些发现为寄生杂草如何克服寄主防御提供了新的见解，并可能有助于制定控制独脚金和其他寄生杂草的新策略，从而提高全球作物生产力和粮食安全。