Molecular Cell Biology, Botanical Institute 1, Karlsruhe Institute of Technology, Karlsruhe, Germany.
PLoS One. 2012;7(7):e40446. doi: 10.1371/journal.pone.0040446. Epub 2012 Jul 6.
Plants can activate defence to pathogen attack by two layers of innate immunity: basal immunity triggered by pathogen-associated molecular pattern (PAMP) triggered immunity (PTI) and effector-triggered immunity (ETI) linked with programmed cell death. Flg22 and Harpin are evolutionary distinct bacterial PAMPs. We have previously shown that Harpin triggers hypersensitive cell death mimicking ETI in Vitis rupestris, but not in the Vitis vinifera cultivar 'Pinot Noir'. In contrast, the bacterial PAMP flg22 activating PTI does not trigger cell death. To get insight into the defence signalling triggered by flg22 and Harpin, we compared cellular responses upon flg22 and Harpin treatment in the two Vitis cell lines. We found that extracellular alkalinisation was blocked by inhibition of calcium influx, and modulated by pharmacological manipulation of the cytoskeleton and mitogen-activated protein kinase activity with quantitative differences between cell lines and type of PAMPs. In addition, an oxidative burst was detected that was much stronger and faster in response to Harpin as compared to flg22. In V. rupestris, both flg22 and Harpin induced transcripts of defence-related genes including stilbene synthase, microtubule disintegration and actin bundling in a similar way, whereas they differed in V. vinifera cv. 'Pinot Noir'. In contrast to Harpin, flg22 failed to trigger significant levels of the stilbene trans-resveratrol, and did not induce hypersensitive cell death even in the highly responsive V. rupestris. We discuss these data in a model, where flg22- and Harpin-triggered defence shares a part of early signal components, but differs in perception, oxidative burst, and integration into a qualitatively different stilbene output, such that for flg22 a basal PTI is elicited in both cell lines, while Harpin induces cell death mimicking an ETI-like pattern of defence.
由病原体相关分子模式（PAMP）触发的基础免疫（PTI）和与程序性细胞死亡相关的效应物触发的免疫（ETI）。Flg22 和 Harpin 是进化上不同的细菌 PAMP。我们之前已经表明，Harpin 触发类似于 ETI 的过敏性细胞死亡，模仿葡萄藤中的 Vitis rupestris，但不在酿酒葡萄品种 'Pinot Noir' 中。相反，激活 PTI 的细菌 PAMP flg22 不会触发细胞死亡。为了深入了解 flg22 和 Harpin 触发的防御信号，我们比较了这两种葡萄细胞系在 flg22 和 Harpin 处理后的细胞反应。我们发现，细胞外碱化作用被钙内流抑制所阻断，并通过细胞骨架和丝裂原活化蛋白激酶活性的药理学操纵进行调节，细胞系和 PAMP 类型之间存在定量差异。此外，检测到氧化爆发，与 flg22 相比，Harpin 引起的氧化爆发更强、更快。在 V. rupestris 中，flg22 和 Harpin 以相似的方式诱导包括芪合酶、微管解体和肌动蛋白捆绑在内的防御相关基因的转录，而在 V. vinifera cv. 'Pinot Noir' 中则不同。与 Harpin 不同，flg22 未能引发显著水平的芪类反式白藜芦醇，即使在高度敏感的 V. rupestris 中也未能引发过敏性细胞死亡。我们在一个模型中讨论了这些数据，其中 flg22 和 Harpin 触发的防御共享一部分早期信号成分，但在感知、氧化爆发和整合为定性不同的芪类输出方面存在差异，因此对于 flg22，两种细胞系都引发了基础 PTI，而 Harpin 诱导类似于 ETI 样防御模式的细胞死亡。
