Michael Smith Laboratories, University of British Columbia, Vancouver BC V6T 1Z4, Canada.
Department of Botany, University of British Columbia, Vancouver BC V6T 1Z4, Canada.
Essays Biochem. 2022 Sep 30;66(5):485-500. doi: 10.1042/EBC20210097.
To perceive pathogen threats, plants utilize both plasma membrane-localized and intracellular receptors. Nucleotide-binding domain leucine-rich repeat containing (NLR) proteins are key receptors that can recognize pathogen-derived intracellularly delivered effectors and activate downstream defense. Exciting recent findings have propelled our understanding of the various recognition and activation mechanisms of plant NLRs. Some NLRs directly bind to effectors, but others can perceive effector-induced changes on targeted host proteins (guardees), or non-functional host protein mimics (decoys). Such guarding strategies are thought to afford the host more durable resistance to quick-evolving and diverse pathogens. Here, we review classic and recent examples of indirect effector recognition by NLRs and discuss strategies for the discovery and study of new NLR-decoy/guardee systems. We also provide a perspective on how executor NLRs and helper NLRs (hNLRs) provide recognition for a wider range of effectors through sensor NLRs and how this can be considered an expanded form of indirect recognition. Furthermore, we summarize recent structural findings on NLR activation and resistosome formation upon indirect recognition. Finally, we discuss existing and potential applications that harness NLR indirect recognition for plant disease resistance and crop resilience.
为了感知病原体威胁，植物利用质膜定位和细胞内受体。核苷酸结合结构域富含亮氨酸重复蛋白 (NLR) 是能够识别病原体来源的细胞内递效因子并激活下游防御的关键受体。令人兴奋的最新发现推动了我们对植物 NLR 各种识别和激活机制的理解。一些 NLR 可以直接结合效应子，而另一些则可以感知效应子在靶向宿主蛋白（守卫者）上引起的变化，或非功能宿主蛋白模拟物（诱饵）。这种守卫策略被认为为宿主提供了对快速进化和多样化的病原体更持久的抗性。在这里，我们回顾了 NLR 间接识别经典和最新的例子，并讨论了发现和研究新的 NLR 诱饵/守卫系统的策略。我们还提供了一个视角，说明执行器 NLR 和辅助 NLR (hNLR) 如何通过传感器 NLR 为更广泛的效应子提供识别，以及这如何被视为间接识别的扩展形式。此外，我们总结了最近关于 NLR 激活和间接识别后抵抗体形成的结构发现。最后，我们讨论了利用 NLR 间接识别提高植物抗病性和作物弹性的现有和潜在应用。
