Glycosylation Regulates Specific Induction of Rice Immune Responses by Acidovorax avenae Flagellin
Glycosylation Regulates Specific Induction of Rice Immune Responses by Acidovorax avenae Flagellin
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DOI：
10.1074/jbc.m111.254029
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发表时间：
2011-07-22
影响因子：
4.8
通讯作者：
Che, Fang-Sik
中科院分区：
文献类型：
--
作者：
Hirai, Hiroyuki;Takai, Ryota;Che, Fang-Sik
植物有一个敏感的系统，可以检测各种病原体衍生的分子，以防止感染。水稻革兰氏阴性植物病原菌Acidovorax avenae无毒菌株N1141的鞭毛蛋白是细菌鞭毛的主要成分，能诱导植物产生H2O2等免疫反应，而水稻毒力菌株a . avenae K1的鞭毛蛋白则不能诱导这些免疫反应。为了阐明导致K1和N1141鞭毛蛋白之间这些不同反应的分子机制，利用大肠杆菌表达系统生成了重组K1和N1141鞭毛蛋白。当用重组K1或N1141鞭毛蛋白处理培养的水稻细胞时，两种鞭毛蛋白同样诱导H2O2生成，这表明鞭毛蛋白的翻译后修饰参与了特异性诱导免疫应答。使用糖基转移酶缺陷突变体的质谱分析显示，N1141和K1的鞭毛蛋白上分别存在1600 - da和2150 - da聚糖。去糖基化的K1鞭毛蛋白以与N1141鞭毛蛋白相同的方式诱导免疫反应。位点定向突变发现，聚糖附着在K1鞭毛蛋白的4个氨基酸残基上（Ser（178）、Ser（183）、Ser（212）和Thr(351)）。在突变体K1鞭毛蛋白中，每个聚糖附着的氨基酸残基都变成了丙氨酸、S178A和S183A， K1鞭毛蛋白在培养的水稻细胞中诱导了强烈的免疫反应，这表明K1鞭毛蛋白中Ser（178）和Ser（183）上的聚糖阻止了水稻对表位的识别。
Plants have a sensitive system that detects various pathogen-derived molecules to protect against infection. Flagellin, a main component of the bacterial flagellum, from the rice avirulent N1141 strain of the Gram-negative phytopathogenic bacterium Acidovorax avenae induces plant immune responses including H2O2 generation, whereas flagellin from the rice virulent K1 strain of A. avenae does not induce these immune responses. To clarify the molecular mechanism that leads to these differing responses between the K1 and N1141 flagellins, recombinant K1 and N1141 flagellins were generated using an Escherichia coli expression system. When cultured rice cells were treated with recombinant K1 or N1141 flagellin, both flagellins equally induced H2O2 generation, suggesting that post-translational modifications of the flagellins are involved in the specific induction of immune responses. Mass spectrometry analyses using glycosyltransferase-deficient mutants showed that 1,600- and 2,150-Da glycans were present on the flagellins from N1141 and K1, respectively. A deglycosylated K1 flagellin induced immune responses in the same manner as N1141 flagellin. Site-directed mutagenesis revealed that glycans were attached to four amino acid residues (Ser(178), Ser(183), Ser(212), and Thr(351)) in K1 flagellin. Among mutant K1 flagellins in which each glycan-attached amino acid residue was changed to alanine, S178A and S183A, K1 flagellin induced a strong immune response in cultured rice cells, indicating that the glycans at Ser(178) and Ser(183) in K1 flagellin prevent epitope recognition in rice.