Plant elicitor peptides (Peps) are conserved regulators of defense responses and models for the study of damage‐associated molecular pattern‐induced immunity. Although present as multigene families in most species, the functional relevance of these multigene families remains largely undefined. While Arabidopsis Peps appear largely redundant in function, previous work examining Pep‐induced responses in maize (Zm) implied specificity of function. To better define the function of individual ZmPeps and their cognate receptors (ZmPEPRs), activities were examined by assessing changes in defense‐associated phytohormones, specialized metabolites and global gene expression patterns, in combination with heterologous expression assays and analyses of CRISPR/Cas9‐generated knockout plants. Beyond simply delineating individual ZmPep and ZmPEPR activities, these experiments led to a number of new insights into Pep signaling mechanisms. ZmPROPEP and other poaceous precursors were found to contain multiple active Peps, a phenomenon not previously observed for this family. In all, seven new ZmPeps were identified and the peptides were found to have specific activities defined by the relative magnitude of their response output rather than by uniqueness. A striking correlation was observed between individual ZmPep‐elicited changes in levels of jasmonic acid and ethylene and the magnitude of induced defense responses, indicating that ZmPeps may collectively regulate immune output through rheostat‐like tuning of phytohormone levels. Peptide structure–function studies and ligand–receptor modeling revealed structural features critical to the function of ZmPeps and led to the identification of ZmPep5a as a potential antagonist peptide able to competitively inhibit the activity of other ZmPeps, a regulatory mechanism not previously observed for this family.

中文翻译：

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玉米植物激发子肽作为免疫信号和食草动物抗性介体的差异活性

植物激发子肽（Peps）是防御反应和模型的保守调节物，用于研究与损伤相关的分子模式诱导的免疫力。尽管在大多数物种中以多基因家族的形式存在，但这些多基因家族的功能相关性在很大程度上仍不确定。虽然拟南芥的败血症在功能上似乎是多余的，但先前研究Pep诱导的玉米（Zm）反应的工作暗示了功能的特异性。为了更好地定义单个ZmPeps及其同源受体（ZmPEPRs）的功能，通过评估防御相关植物激素，专门代谢产物和整体基因表达模式的变化，并结合异源表达测定和CRISPR / Cas9生成的分析，来检查活性剔除植物。除了简单地描述各个ZmPep和ZmPEPR活动之外，这些实验对Pep信号机制产生了许多新见解。发现ZmPROPEP和其他粘性前体含有多种活性胃蛋白酶，这一现象以前在该家族中未发现。总共鉴定出七种新的ZmPeps，发现这些肽具有特定活性，这些活性是由其响应输出的相对大小而不是唯一性决定的。在各个ZmPep引起的茉莉酸和乙烯水平变化与诱导的防御反应强度之间发现了惊人的相关性，这表明ZmPeps可能通过变态调节剂调节植物激素水平来共同调节免疫输出。