We evaluated the ability of metabolic elicitors extracted from Pseudomonas fluorescens N21.4 to induce systemic resistance (ISR) in Arabidopsis thaliana against the pathogen Pseudomonas syringae DC3000. Metabolic elicitors were obtained from bacteria-free culture medium with n-hexane, ethyl acetate and n-butanol in three consecutive extractions. Each extract showed plant protection activity. The n-hexane fraction was the most effective and was used to study the signal transduction pathways involved by evaluating expression of marker genes of the salicylic acid (SA) signalling pathway (NPR1, PR1, ICS and PR2) and the jasmonic acid/ethylene (JA/ET) signalling pathway (PDF1, MYC2, LOX2 and PR3). In addition, the level of oxidative stress was tested by determining the activity of enzymes related to the ascorbate-glutathione cycle. N-hexane extracts stimulated both pathways based on overexpression of ICS, PR1, PR2, PDF1 and LOX2 genes. In addition, activity of the pathogenesis-related proteins glucanase (PR2) and chitinase (PR3), lipoxygenase and polyphenol oxidase was enhanced together with an increased capacity to remove reactive oxygen species (ROS). This was associated with less oxidative stress as indicated by a decrease in malondialdehyde (MDA), suggesting a causative link between defensive metabolism against P. syringae and ROS scavenging.

中文翻译：

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荧光假单胞菌培养物的提取物诱导基因表达和酶活性的防御模式，同时抑制受到致病性丁香假单胞菌攻击的拟南芥中可见的损伤和活性氧。

我们评估了从荧光假单胞菌 N21.4 中提取的代谢诱导子在拟南芥中诱导针对病原体丁香假单胞菌 DC3000 的系统抗性 (ISR) 的能力。通过正己烷、乙酸乙酯和正丁醇连续三次提取，从无菌培养基中获得代谢诱导子。每种提取物均显示出植物保护活性。正己烷组分是最有效的，用于通过评估水杨酸 (SA) 信号通路（NPR1、PR1、ICS 和 PR2）和茉莉酸/乙烯（ JA/ET) 信号通路（PDF1、MYC2、LOX2 和 PR3）。此外，通过测定与抗坏血酸-谷胱甘肽循环相关的酶的活性来测试氧化应激水平。正己烷提取物刺激基于 ICS、PR1、PR2、PDF1 和 LOX2 基因过度表达的两条途径。此外，发病机制相关蛋白葡聚糖酶（PR2）和几丁质酶（PR3）、脂氧合酶和多酚氧化酶的活性增强，同时去除活性氧（ROS）的能力也增强。这与丙二醛 (MDA) 减少所表明的氧化应激减少有关，表明丁香假单胞菌的防御性代谢与 ROS 清除之间存在因果关系。