National Key Laboratory of Green Pesticide, Integrative Microbiology Research Centre, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China.
College of Horticulture Science, South China Agricultural University, Guangzhou 510642, China.
Pestic Biochem Physiol. 2023 Aug;194:105471. doi: 10.1016/j.pestbp.2023.105471. Epub 2023 May 16.
Pseudomonas syringae (P. syringae) is a highly prevalent Gram-negative pathogen with over 60 pathogenic variants that cause yield losses of up to 80% in various crops. Traditional control methods mainly involve the application of antibiotics to inactivate pathogenic bacteria, but large-scale application of antibiotics has led to the development of bacterial resistance. Gram-negative pathogens including P. syringae commonly use the type III secretion system (T3SS) as a transport channel to deliver effector proteins into host cells, disrupting host defences and facilitating virulence, providing a novel target for antibacterial drug development. In this study, we constructed a high-throughput screening reporter system based on our previous work to screen for imidazole, oxazole and thiazole compounds. The screening indicated that the three compounds (II-14, II-15 and II-24) significantly inhibited hrpW and hrpL gene promoter activity without influencing the growth of P. syringae, and the inhibitory activity was better than that of the positive control sulforaphane (4-methylsulfinylbutyl isothiocyanate, SFN) at 50 μM. Three compounds suppressed the transcript levels of representative T3SS genes to different degrees, suggesting that the compounds may suppress the expression of T3SS by modulating the HrpR/S-HrpL regulatory pathway. Inoculation experiments indicated that all three compounds suppressed the pathogenicity of Pseudomonas syringae pv. tomato DC3000 in tomato and Pseudomonas syringae pv. phaseolicola 1448A in bean to varying degrees. One representative compound, II-15, significantly inhibited the secretion of the Pst DC3000 AvrPto effector protein. These findings provide a theoretical basis for the development of novel P. syringae T3SS inhibitors for application in disease prevention and control.
丁香假单胞菌（Pseudomonas syringae）是一种广泛存在的革兰氏阴性病原体，有超过 60 种致病变体，可导致各种作物的产量损失高达 80%。传统的控制方法主要涉及应用抗生素来灭活致病细菌，但抗生素的大规模应用导致了细菌耐药性的发展。包括丁香假单胞菌在内的革兰氏阴性病原体通常使用 III 型分泌系统（T3SS）作为运输通道，将效应蛋白输送到宿主细胞中，破坏宿主防御并促进毒力，为抗菌药物的开发提供了一个新的目标。在本研究中，我们在之前的工作基础上构建了一个基于高通量筛选的报告系统，用于筛选咪唑、噁唑和噻唑化合物。筛选表明，这三种化合物（II-14、II-15 和 II-24）显著抑制了 hrpW 和 hrpL 基因启动子的活性，而不影响丁香假单胞菌的生长，其抑制活性在 50 μM 时优于阳性对照物萝卜硫素（4-甲基亚磺酰基丁基异硫氰酸酯，SFN）。三种化合物在不同程度上抑制了代表性 T3SS 基因的转录水平，这表明这些化合物可能通过调节 HrpR/S-HrpL 调控途径来抑制 T3SS 的表达。接种实验表明，这三种化合物都不同程度地抑制了丁香假单胞菌 pv. tomato DC3000 在番茄和丁香假单胞菌 pv. phaseolicola 1448A 在豆类中的致病性。一种代表性化合物 II-15，显著抑制了 Pst DC3000 AvrPto 效应蛋白的分泌。这些发现为开发新型丁香假单胞菌 T3SS 抑制剂用于疾病预防和控制提供了理论依据。
