Plant elicitor peptide 1 fortifies root cell walls and triggers a systemic root-to-shoot immune signaling in Arabidopsis

Plant immunity is initiated by cell surface-localized receptors upon perception of pathogen-derived microbe or pathogen-associated molecular patterns (MAMPs/PAMPs), damage/danger-associated molecular patterns (DAMPs), and phytocytokines. Different patterns activate highly overlapping immune signaling at the early stage but divergent physiological responses at the late stage. Here, we indicate that plant elicitor peptide 1 (Pep1), a well-known DAMP, induces lignin and callose depositions, two types of late immune responses for strengthening the plant cell wall. Pep1-induced lignin and callose depositions in Arabidopsis root rely on early signaling components for Pep1 perception and signaling propagation. The phytohormone jasmonic acid and ethylene differently regulate the Pep1-regulated cell wall consolidation. Pep1 application in root also triggers a systemic immune signaling in shoot, and reactive oxygen species (ROS) is essential for the signaling communication between root and shoot. Collectively, the study reveals that Pep1 strengthens cell walls in root and triggers a systemic immune signaling from root to shoot.植物免疫由定位于细胞表面的受体（cell surface-localized receptors）启动，此类受体可识别病原体衍生的微生物或病原体相关分子模式（MAMPs/PAMPs）、损伤/危险相关分子模式（DAMPs）以及植物细胞因子（phytocytokines）。不同的触发模式在免疫早期会激活高度重叠的免疫信号通路，但在晚期则引发分化的生理响应。本研究表明，作为经典损伤相关分子模式的植物激发肽1（Pep1），可诱导木质素（lignin）与胼胝质（callose）沉积这两类用于强化植物细胞壁的晚期免疫响应。在拟南芥（Arabidopsis）根系中，Pep1诱导的木质素与胼胝质沉积依赖于参与Pep1识别与信号传导的早期信号组分。植物激素茉莉酸（jasmonic acid）与乙烯（ethylene）对Pep1介导的细胞壁加固过程具有差异性调控作用。在根系中施加Pep1还可触发地上部分的系统性免疫信号传导，而活性氧（ROS）是根系与地上部分间信号通讯的必需组分。综上，本研究揭示Pep1可强化拟南芥根系的细胞壁，并触发从根系到地上部分的系统性免疫信号传导。