Summary Effector proteins are central to the success of plant pathogens, while immunity in host plants is driven by receptor‐mediated recognition of these effectors. Understanding the molecular details of effector–receptor interactions is key for the engineering of novel immune receptors. Here, we experimentally determined the crystal structure of the Puccinia graminis f. sp. tritici (Pgt) effector AvrSr27, which was not accurately predicted using AlphaFold2. We characterised the role of the conserved cysteine residues in AvrSr27 using in vitro biochemical assays and examined Sr27‐mediated recognition using transient expression in Nicotiana spp. and wheat protoplasts. The AvrSr27 structure contains a novel β‐strand rich modular fold consisting of two structurally similar domains that bind to Zn2+ ions. The N‐terminal domain of AvrSr27 is sufficient for interaction with Sr27 and triggering cell death. We identified two Pgt proteins structurally related to AvrSr27 but with low sequence identity that can also associate with Sr27, albeit more weakly. Though only the full‐length proteins, trigger Sr27‐dependent cell death in transient expression systems. Collectively, our findings have important implications for utilising protein prediction platforms for effector proteins, and those embarking on bespoke engineering of immunity receptors as solutions to plant disease.

中文翻译：

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AvrSr27 是一种锌结合效应子，具有对免疫识别很重要的模块化结构

概括 效应蛋白对于植物病原体的成功至关重要，而宿主植物的免疫是由受体介导的对这些效应蛋白的识别驱动的。了解效应器-受体相互作用的分子细节是新型免疫受体工程的关键。 在这里，我们通过实验确定了晶体结构禾本科柄锈菌F。 sp。小麦（PGT）效应子 AvrSr27，使用 AlphaFold2 无法准确预测。我们使用 AvrSr27 中保守的半胱氨酸残基的作用进行了表征体外生化测定并使用瞬时表达检查 Sr27 介导的识别烟草属种。和小麦原生质体。 AvrSr27 结构包含一种新颖的富含 β 链的模块化折叠，由两个与 Zn 结合的结构相似的结构域组成2+离子。 AvrSr27 的 N 端结构域足以与 Sr27 相互作用并触发细胞死亡。我们确定了两个PGT结构上与 AvrSr27 相关但序列同一性较低的蛋白质也可以与 Sr27 关联，尽管更弱。尽管只有全长蛋白质，但会在瞬时表达系统中触发 Sr27 依赖性细胞死亡。 总的来说，我们的研究结果对于利用效应蛋白的蛋白质预测平台以及那些着手定制免疫受体工程作为植物病害解决方案的人具有重要意义。