Department of Biochemistry, Duke University School of Medicine, Durham, NC 27708, USA.
Howard Hughes Medical Institute, Duke University, Durham, NC 27708, USA; Department of Biology, PO Box 90338, Duke University, Durham, NC 27708, USA.
Curr Opin Plant Biol. 2023 Jun;73:102352. doi: 10.1016/j.pbi.2023.102352. Epub 2023 Mar 17.
In the past 30 years, our knowledge of how nonexpressor of pathogenesis-related genes 1 (NPR1) serves as a master regulator of salicylic acid (SA)-mediated immune responses in plants has been informed largely by molecular genetic studies. Despite extensive efforts, the biochemical functions of this protein in promoting plant survival against a wide range of pathogens and abiotic stresses are not completely understood. Recent breakthroughs in cellular and structural analyses of NPR1 and its paralogs have provided a molecular framework for reinterpreting decades of genetic observations and have revealed new functions of these proteins. Besides NPR1's well-known nuclear activity in inducing stress-responsive genes, it has also been shown to control stress protein homeostasis in the cytoplasm. Structurally, NPR4's direct binding to SA has been visualized at the molecular level. Analysis of the cryo-EM and crystal structures of NPR1 reveals a bird-shaped homodimer containing a unique zinc finger. Furthermore, the TGA3-NPR1-TGA3 complex has been imaged, uncovering a dimeric NPR1 bridging two TGA3 transcription factor dimers as part of an enhanceosome complex to induce defense gene expression. These new findings will shape future research directions for deciphering NPR functions in plant immunity.
在过去的 30 年里，我们对非致病相关基因 1（NPR1）如何作为植物中水杨酸（SA）介导免疫反应的主调控因子的了解，主要是通过分子遗传学研究获得的。尽管付出了巨大的努力，但该蛋白在促进植物对各种病原体和非生物胁迫的生存方面的生化功能仍未完全理解。最近对 NPR1 及其同源物的细胞和结构分析的突破，为重新解释几十年来的遗传观察结果提供了一个分子框架，并揭示了这些蛋白的新功能。除了 NPR1 在诱导应激响应基因方面众所周知的核活性外，它还被证明可以控制细胞质中的应激蛋白稳态。结构上，已经在分子水平上可视化了 NPR4 与 SA 的直接结合。对 NPR1 的冷冻电镜和晶体结构的分析揭示了一个具有独特锌指的鸟形同源二聚体。此外，还对 TGA3-NPR1-TGA3 复合物进行了成像，揭示了二聚体 NPR1 作为增强子复合物的一部分桥接两个 TGA3 转录因子二聚体，以诱导防御基因表达。这些新发现将为破译 NPR 在植物免疫中的功能指明未来的研究方向。
