• Signaling peptides play crucial roles in plant growth, development and defense. We report here that the Arabidopsis thaliana secreted peptide, ROOT MERISTEM GROWTH FACTOR 7 (RGF7), functions as an endogenous elicitor to trigger plant immunity.
• Expression of the RGF7 precursor‐encoding gene (preRGF7) is highly induced in Arabidopsis leaves upon infection by the bacterial pathogen Pseudomonas syringae. The pathogen‐responsive preRGF7 expression is regulated by the transcription factor WRKY33 and its upstream mitogen‐activated protein kinases MPK3/MPK6 and calcium‐dependent protein kinases CPK5/CPK6. In the absence of pathogen attack, chemically induced expression of preRGF7 in transgenic Arabidopsis plants was sufficient to trigger immune responses. Pre‐induction of preRGF7 expression in transgenic Arabidopsis also led to enhanced immune responses and increased resistance to P. syringae infection.
• Biochemical and genetic analyses demonstrated that RGF7 is perceived by the leaf‐expressed RGF1 INSENSITIVE (RGI) family receptors RGI4 and RGI5. The SOMATIC EMBRYOGENESIS RECEPTOR KINASES (SERKs) BAK1 and SERK4 are also involved in RGF7 perception via forming RGF7‐induced receptor‐complexes with RGI4 and RGI5.
• These results indicate that the pathogen‐induced RGF7 peptide, perceived by the RGI4/RGI5‐BAK1/SERK4 receptor complexes, acts as a new damage‐associated molecular pattern (DAMP) and plays a significant role in Arabidopsis immunity.

中文翻译：

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受体样激酶RGI4和RGI5感知病原体诱导的肽RGF7触发拟南芥的先天免疫

• 信号肽在植物生长，发育和防御中起关键作用。我们在这里报告，拟南芥分泌的肽，根系生长因子7（RGF7），作为触发植物免疫力的内源激发子。
• 受到细菌病原体丁香假单胞菌感染后，拟南芥叶片中高度诱导了RGF7前体编码基因（preRGF7）的表达。病原体响应性preRGF7的表达受转录因子WRKY33及其上游的促分裂原活化蛋白激酶MPK3 / MPK6和钙依赖性蛋白激酶CPK5 / CPK6调控。在没有病原体攻击的情况下，转基因拟南芥植物中化学诱导的preRGF7表达足以触发免疫反应。preRGF7表达在转基因拟南芥中的预诱导也导致增强的免疫反应和增强的对P的抗性。 丁香科感染。
• 生化和基因分析表明，RGF7被叶表达的RGF1不敏感（RGI）家族受体RGI4和RGI5感知。体细胞胚发生受体激酶（SERKs）BAK1和SERK4也通过与RGI4和RGI5形成RGF7诱导的受体复合物而参与RGF7的感知。
• 这些结果表明，由RGI4 / RGI5-BAK1 / SERK4受体复合物感知的病原体诱导的RGF7肽可作为一种新的损伤相关分子模式（DAMP），并在拟南芥免疫中发挥重要作用。