Small post-translationally modified peptides are important signalling components of plant defence responses against phytopathogens, acting as both positive and negative modulators. PAMP-INDUCED SECRETED PEPTIDE (PIP) 1 and 2 have been shown to amplify plant immunity. Here we investigate the role of the related peptide PIP3 in the regulation of immune response in Arabidopsis. Treatment with synthetic PIP peptides led to similar transcriptome reprogramming, indicating an effect on innate immunity-related processes and phytohormones, including jasmonic acid (JA) biosynthesis and signalling. PIP3 overexpressing (OX) plants showed enhanced growth inhibition in response to flg22 exposure. In addition, flg22-induced production of reactive oxygen species and callose deposition was significantly reduced in PIP3-OX plants. Interestingly, PIP3-OX plants showed increased susceptibility toward both Botrytis cinerea and the biotrophic pathogen Pseudomonas syringae. Expression of both JA and salicylic acid (SA) biosynthesis and signalling genes was more induced during B. cinerea infection in PIP3-OX plants compared with wild-type plants. Promoter and ChIP-seq analyses indicated that the transcription factors WRKY18, WRKY33, and WRKY40 cooperatively act as repressors for PIP3. The results point to a fine-tuning role for PIP3 in modulation of immunity through the regulation of SA and JA biosynthesis and signalling pathways in Arabidopsis.

中文翻译：

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PAMP诱导的分泌肽3调节拟南芥中的免疫力。

小的翻译后修饰的肽是植物对抗植物病原体的防御反应的重要信号成分，既充当正调节剂又充当负调节剂。PAMP诱导的分泌肽（PIP）1和2已显示出增强植物免疫力的能力。在这里，我们调查了拟南芥中相关肽PIP3在调节免疫应答中的作用。合成PIP肽的处理导致类似的转录组重编程，表明对先天性免疫相关过程和植物激素（包括茉莉酸（JA）生物合成和信号转导）的影响。PIP3过表达（OX）植物响应flg22暴露表现出增强的生长抑制作用。另外，在PIP3-OX植物中，flg22诱导的活性氧种类的产生和call的沉积显着降低。有趣的是，PIP3-OX植物显示出对灰葡萄孢和生养性病原体丁香假单胞菌的敏感性增加。与野生型植物相比，在PIP3-OX植物中灰质芽孢杆菌感染期间，JA和水杨酸（SA）生物合成和信号转导基因的表达均被诱导。启动子和ChIP-seq分析表明，转录因子WRKY18，WRKY33和WRKY40协同充当PIP3的阻遏物。结果表明，PIP3通过调节拟南芥中SA和JA生物合成以及信号传导途径，在调节免疫力方面具有微调作用。与野生型植物相比，PIP3-OX植物中的灰霉病感染。启动子和ChIP-seq分析表明，转录因子WRKY18，WRKY33和WRKY40协同充当PIP3的阻遏物。结果表明，PIP3通过调节拟南芥中SA和JA生物合成以及信号传导途径，在调节免疫力方面具有微调作用。与野生型植物相比，PIP3-OX植物中的灰霉病感染。启动子和ChIP-seq分析表明，转录因子WRKY18，WRKY33和WRKY40协同充当PIP3的阻遏物。结果表明，PIP3通过调节拟南芥中SA和JA生物合成以及信号传导途径，在调节免疫力方面具有微调作用。