Department of Plant Pathology and Microbiology, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
Department of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon Lezion 7528809, Israel.
ACS Chem Biol. 2020 Jul 17;15(7):1883-1891. doi: 10.1021/acschembio.0c00185. Epub 2020 May 22.
Salicylic acid (SA) is a hormone that mediates systemic acquired resistance in plants. We demonstrated that SA can interfere with group behavior and virulence of the soft-rot plant pathogen spp. through quorum sensing (QS) inhibition. QS is a population density-dependent communication system that relies on the signal molecule acyl-homoserine lactone (AHL) to synchronize infection. mutants, lacking the QS AHL synthase () or the response regulator (), were used to determine how SA inhibits QS. ExpI was expressed in DH5α, the QS negative strain of , revealing direct interference of SA with AHL synthesis. Docking simulations showed SA is a potential ExpI ligand. This hypothesis was further confirmed by direct binding of SA to purified ExpI, shown by isothermal titration calorimetry and microscale thermophoresis. Computational alanine scanning was employed to design a mutant ExpI with predicted weaker binding affinity to SA. The mutant was constructed and displayed lower affinity to the ligand in the binding assay, and its physiological inhibition by SA was reduced. Taken together, these data support a likely mode of action and a role for SA as potent inhibitor of AHL synthase and QS.
水杨酸（SA）是一种激素，可介导植物的系统获得性抗性。我们证明，SA 可以通过群体感应（QS）抑制来干扰软腐病植物病原体的群体行为和毒力。QS 是一种依赖于信号分子酰高丝氨酸内酯（AHL）的种群密度依赖性通讯系统，用于同步感染。我们使用缺乏 QS AHL 合酶（）或响应调节剂（）的突变体来确定 SA 如何抑制 QS。ExpI 在 DH5α 中表达，这是 的 QS 阴性菌株，表明 SA 直接干扰 AHL 的合成。对接模拟表明，SA 是 ExpI 的潜在配体。该假设通过等温滴定量热法和微尺度热泳直接结合实验进一步得到证实。通过计算丙氨酸扫描设计了一种具有预测较弱与 SA 结合亲和力的突变 ExpI。构建了该突变体，并在结合实验中显示出对配体的亲和力较低，其生理抑制作用被降低。综上所述，这些数据支持了 SA 作为 AHL 合酶和 QS 有效抑制剂的作用模式和作用。
