Flagellin perception is a keystone of pattern-triggered immunity in plants. The recognition of this protein by a plasma membrane (PM) receptor complex is the beginning of a signaling cascade that includes protein phosphorylation and the production of reactive oxygen species (ROS). In both Arabidopsis (Arabidopsis thaliana) seedlings and suspension cells, we found that treatment with flg22, a peptide corresponding to the most conserved domain of bacterial flagellin, caused a rapid and transient decrease in the level of phosphatidylinositol (PI) 4,5-bisphosphate along with a parallel increase in phosphatidic acid (PA). In suspension cells, inhibitors of either phosphoinositide-dependent phospholipases C (PLC) or diacylglycerol kinases (DGKs) inhibited flg22-triggered PA production and the oxidative burst. In response to flg22, receptor-like kinase-deficient fls2, bak1, and bik1 mutants (FLAGELLIN SENSITIVE 2, BRASSINOSTEROID INSENSITIVE 1-associated kinase 1, and BOTRYTIS-INDUCED KINASE 1, respectively) produced less PA than wild-type (WT) plants, whereas this response did not differ in NADPH oxidase-deficient rbohD (RESPIRATORY BURST OXIDASE HOMOLOG D) plants. Among the DGK-deficient lines tested, the dgk5.1 mutant produced less PA and less ROS after flg22 treatment compared with WT seedlings. In response to flg22, dgk5.1 plants showed lower callose accumulation and impaired resistance to Pseudomonas syringae pv. tomato DC3000 hrcC-. Transcriptomics revealed that the basal expression of defense-related genes was altered in dgk5.1 seedlings compared with the WT. A GFP-DGK5 fusion protein localized to the PM, where RBOHD and PLC2 (proteins involved in plant immunity) are also located. The role of DGK5 and its enzymatic activity in flagellin signaling and fine-tuning of early immune responses in plant-microbe interactions is discussed.

中文翻译：

---

DIACYLGLYCEROL KINASE 5 参与拟南芥中鞭毛蛋白诱导的信号传导。

鞭毛蛋白感知是植物模式触发免疫的基石。质膜 (PM) 受体复合物对这种蛋白质的识别是信号级联反应的开始，包括蛋白质磷酸化和活性氧 (ROS) 的产生。在拟南芥 (Arabidopsis thaliana) 幼苗和悬浮细胞中，我们发现用 flg22（一种对应于细菌鞭毛蛋白最保守结构域的肽）处理会导致磷脂酰肌醇 (PI) 4,5-二磷酸水平快速和短暂降低随着磷脂酸（PA）的平行增加。在悬浮细胞中，磷酸肌醇依赖性磷脂酶 C (PLC) 或二酰基甘油激酶 (DGK) 的抑制剂可抑制 flg22 触发的 PA 产生和氧化爆发。作为对 flg22 的回应，受体样激酶缺陷型 fls2、bak1 和 bik1 突变体（分别为 FLAGELLIN SENSITIVE 2、BRASSINOSTEROID INSENSITIVE 1 相关激酶 1 和 BOTRYTIS 诱导的激酶 1）产生的 PA 比野生型 (WT) 植物少，而这种反应在 NADPH 氧化酶缺陷型 rbohD (RESSPIRATORY BURST OXIDASE HOMOLOG D) 植物中没有差异。在测试的DGK缺陷系中，与WT幼苗相比，dgk5.1突变体在flg22处理后产生更少的PA和更少的ROS。作为对 flg22 的响应，dgk5.1 植物表现出较低的胼胝质积累和对丁香假单胞菌 pv 的抗性受损。番茄 DC3000 hrcC-. 转录组学显示，与 WT 相比，dgk5.1 幼苗中防御相关基因的基础表达发生了改变。一种定位于 PM 的 GFP-DGK5 融合蛋白，RBOHD 和 PLC2（参与植物免疫的蛋白质）也位于其中。讨论了 DGK5 及其酶活性在鞭毛蛋白信号传导和微调植物-微生物相互作用中的早期免疫反应中的作用。