RNA-Seq of Arabidopsis Col-0 and sid2 seedlings treated with L-Glu and urea

Plant resistance inducers (PRIs) are compounds that protect crops from diseases by activating plant immunity. The exogenous treatment with glutamate (Glu), an important amino acid for living organisms, was shown to induce resistance against fungal pathogen in rice and tomato. To understand the molecular mechanism of Glu-induced immunity, we developed a model system using Arabidopsis thaliana. Here, we found that exogenous treatment with Glu to Arabidopsis enhances resistance against Pseudomonas syringae pv. tomato DC3000 and Colletotrichum higginsianum. Consistently, transcriptome analyses of Arabidopsis seedlings treated with Glu showed that Glu significantly induces the expression of wound, defense, and stress related genes. Interestingly, Glu activates the expression of pathogen or damage associated molecular patterns (PAMP or DAMP)–inducible genes at much later time points than PAMP/DAMPs normally do. Moreover, expression of Glu-inducible genes does not require known components of PAMP receptor complex, glutamate receptors, salicylic acid-biosynthesis enzyme, or glutamate decarboxylase. In addition, Glu also enhances PAMP-inducible immune responses, such as production of reactive oxygen species and mitogen-activated protein kinase activation. These results show that Glu activates PAMP/DAMP-triggered immunity signaling pathway in a novel manner. Examination of L-Glu-inducible genes in Arabidopsis Col-0 and sid2 seedlings after 48h treatment.

植物抗病诱导剂（Plant resistance inducers, PRIs）是一类通过激活植物免疫系统以保护作物免受病害侵害的化合物。谷氨酸（glutamate, Glu）作为生物体必需的重要氨基酸，其外源施加已被证实可诱导水稻与番茄产生对真菌病原菌的抗性。为解析谷氨酸诱导免疫的分子机制，本研究构建了以拟南芥（Arabidopsis thaliana）为材料的模式体系。本研究发现，向拟南芥外源施加谷氨酸可增强其对丁香假单胞菌番茄致病变种DC3000（Pseudomonas syringae pv. tomato DC3000）及希金斯炭疽菌（Colletotrichum higginsianum）的抗性。与之相符的是，对谷氨酸处理的拟南芥幼苗开展转录组分析结果显示，谷氨酸可显著诱导创伤、防御及胁迫相关基因的表达。值得关注的是，相较于病原相关分子模式/损伤相关分子模式（pathogen or damage associated molecular patterns, PAMP/DAMP）的常规诱导时效，谷氨酸激活病原/损伤相关分子模式诱导基因表达的时间节点明显滞后。此外，谷氨酸诱导基因的表达并不依赖于已知的病原模式识别受体复合物组分、谷氨酸受体、水杨酸合成酶或谷氨酸脱羧酶。同时，谷氨酸还可增强病原模式诱导的免疫响应，例如活性氧迸发以及丝裂原活化蛋白激酶（mitogen-activated protein kinase, MAPK）的激活。上述结果表明，谷氨酸以全新的方式激活病原/损伤相关分子模式触发的免疫信号通路。本研究还对经48小时处理后的拟南芥Col-0及sid2幼苗中的L-谷氨酸诱导基因进行了检测。