Plasma membrane (PM) depolarization functions as an initial step in plant defense signaling pathways. However, only a few ion channels/transporters have been characterized in the context of plant immunity. Here, we show that the Arabidopsis (Arabidopsis thaliana) Na+:K+:2Cl- (NKCC) cotransporter CCC1 has a dual function in plant immunity. CCC1 functions independently of PM depolarization and negatively regulates pathogen-associated molecular pattern-triggered immunity. However, CCC1 positively regulates plant basal and effector-triggered resistance to Pseudomonas syringae pv. tomato (Pst) DC3000. In line with the compromised immunity to Pst DC3000, ccc1 mutants show reduced expression of genes encoding enzymes involved in the biosynthesis of antimicrobial peptides, camalexin, and 4-OH-ICN, as well as pathogenesis-related proteins. Moreover, genes involved in cell wall and cuticle biosynthesis are constitutively down-regulated in ccc1 mutants, and the cell walls of these mutants exhibit major changes in monosaccharide composition. The role of CCC1 ion transporter activity in the regulation of plant immunity is corroborated by experiments using the specific NKCC inhibitor bumetanide. These results reveal a function for ion transporters in immunity-related cell wall fortification and antimicrobial biosynthesis.

中文翻译：

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阳离子氯化物共转运蛋白1（CCC1）介导植物对丁香假单胞菌的抗性。

质膜（PM）去极化是植物防御信号通路中的第一步。然而，在植物免疫性的背景下，仅表征了少数离子通道/转运蛋白。在这里，我们显示拟南芥（Arabidopsis thaliana）Na +：K +：2Cl-（NKCC）共转运蛋白CCC1在植物免疫中具有双重功能。CCC1的功能独立于PM去极化，并负调控病原体相关的分子模式触发的免疫力。但是，CCC1积极调节植物基础和效应子触发的丁香假单胞菌pv。番茄（Pst）DC3000。与对Pst DC3000的免疫力下降相一致，ccc1突变体显示出编码与抗菌肽，camalexin和4-OH-ICN以及病程相关蛋白的生物合成有关的酶的基因表达降低。而且，在ccc1突变体中，参与细胞壁和表皮生物合成的基因被组成性下调，并且这些突变体的细胞壁在单糖组成中显示出重大变化。使用特定的NKCC抑制剂布美他尼进行的实验证实了CCC1离子转运蛋白活性在调节植物免疫力中的作用。这些结果揭示了离子转运蛋白在免疫相关细胞壁强化和抗菌生物合成中的功能。