Salt stress is a major environmental factor limiting plant growth and productivity. We recently discovered an important new salt tolerance pathway, where the cell wall leucine-rich repeat extensins LRX3/4/5, the RAPID ALKALINIZATION FACTOR (RALF) peptides RALF22/23, and receptor-like kinase FERONIA (FER) function as a module to simultaneously regulate plant growth and salt stress tolerance. However, the intracellular signaling pathways that are regulated by the extracellular LRX3/4/5-RALF22/23-FER module to coordinate growth, cell wall integrity, and salt stress responses are still unknown. Here, we report that the LRX3/4/5-RALF22/23-FER module negatively regulates the levels of jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA). Blocking JA pathway rescues the dwarf phenotype of the lrx345 and fer-4 mutants, while disruption of ABA biosynthesis suppresses the salt-hypersensitivity of these mutants. Many salt stress-responsive genes display abnormal expression patterns in the lrx345 and fer-4 mutants, as well as in the wild type plants treated with epigallocatechin gallate (EGCG), an inhibitor of pectin methylesterases, suggesting cell wall integrity as a critical factor that determines the expression pattern of stress-responsive genes. Production of reactive oxygen species (ROS) is constitutively increased in the lrx345 and fer-4 mutants, and inhibition of ROS accumulation suppresses the salt-hypersensitivity of these mutants. Together, our work provides strong evidence that the LRX3/4/5-RALF22/23-FER module controls plant growth and salt stress responses by regulating hormonal homeostasis and ROS accumulation.

中文翻译：

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LRXs-RALFs-FER 模块通过调节多种植物激素来控制植物生长和盐胁迫反应

盐胁迫是限制植物生长和生产力的主要环境因素。我们最近发现了一个重要的新的耐盐途径，其中富含亮氨酸的重复延伸素 LRX3/4/5、快速碱化因子 (RALF) 肽 RALF22/23 和受体样激酶 FERONIA (FER) 作为一个模块发挥作用同时调节植物生长和盐胁迫耐受性。然而，由细胞外 LRX3/4/5-RALF22/23-FER 模块调节以协调生长、细胞壁完整性和盐胁迫反应的细胞内信号通路仍然未知。在这里，我们报告 LRX3/4/5-RALF22/23-FER 模块负调节茉莉酸 (JA)、水杨酸 (SA) 和脱落酸 (ABA) 的水平。阻断 JA 通路挽救了lrx345的矮化表型和fer-4突变体，而 ABA 生物合成的破坏抑制了这些突变体的盐超敏性。许多盐胁迫响应基因在lrx345和fer-4突变体以及用果胶甲酯酶抑制剂表没食子儿茶素没食子酸酯 (EGCG) 处理的野生型植物中表现出异常表达模式，这表明细胞壁完整性是影响细胞壁完整性的关键因素。决定了应激反应基因的表达模式。lrx345和fer-4中活性氧 (ROS) 的产生持续增加突变体，抑制 ROS 积累可抑制这些突变体的盐超敏性。总之，我们的工作提供了强有力的证据，证明 LRX3/4/5-RALF22/23-FER 模块通过调节激素稳态和 ROS 积累来控制植物生长和盐胁迫反应。