Mol Plant Microbe Interact. 2014 Feb;27(2):113-24. doi: 10.1094/MPMI-10-13-0304-R.
Plants sense potential pathogens by recognizing conserved pathogen-associated molecular patterns (PAMPs) that cause PAMP-triggered immunity (PTI). We previously reported that rice recognizes flagellin from the rice-incompatible N1141 strain of Acidovorax avenae and subsequently induces immune responses. Cell extracts isolated from flagellin-deficient N1141 (Δfla1141) still induced PTI responses, suggesting that Δfla1141 possesses an additional PAMP distinct from flagellin. Here, we show that elongation factor Tu (EF-Tu), one of the most abundant bacterial proteins, acts as a PAMP in rice and causes several PTI responses. In Brassicaceae species, EF-Tu and an N-acetylated peptide comprising the first 18 amino acids of the N-terminus, termed elf18, are fully active as inducers of PTI responses. By contrast, elf18 did not cause any immune responses in rice, whereas an EF-Tu middle region comprising Lys176 to Gly225, termed EFa50, is fully active as a PAMP in rice. In the leaves of rice plants, EF-Tu induced H2O2 generation and callose deposition, and also triggered resistance to coinfection with pathogenic bacteria. Taken together, these data demonstrate that rice recognizes EFa50, which is distinct from elf18, and that this epitope induces PTI responses.
植物通过识别保守的病原体相关分子模式（PAMPs）来感知潜在的病原体，这些 PAMPs 会引发植物的免疫反应（PTI）。我们之前曾报道过，水稻可以识别来自非亲和性的水稻酸噬细胞菌 N1141 菌株的鞭毛蛋白，并随后诱导免疫反应。从鞭毛蛋白缺失的 N1141（Δfla1141）中分离出的细胞提取物仍然可以诱导 PTI 反应，这表明Δfla1141 具有不同于鞭毛蛋白的另一种 PAMP。在这里，我们表明延伸因子 Tu（EF-Tu），一种最丰富的细菌蛋白之一，在水稻中充当 PAMP，并引发几种 PTI 反应。在十字花科植物中，EF-Tu 和包含 N 端前 18 个氨基酸的 N-乙酰化肽，称为 elf18，作为 PTI 反应的诱导剂具有完全的活性。相比之下，elf18 不会在水稻中引起任何免疫反应，而包含赖氨酸 176 到甘氨酸 225 的 EF-Tu 中间区域，称为 EFa50，在水稻中是一种完全有效的 PAMP。在水稻叶片中，EF-Tu 诱导 H2O2 的产生和几丁质的沉积，并引发对致病性细菌共感染的抗性。综上所述，这些数据表明，水稻可以识别 EFa50，它与 elf18 不同，并且这个表位可以诱导 PTI 反应。
