Altered glycosylation of exported proteins, including surface immune receptors, compromises calcium and downstream signaling responses to microbe-associated molecular patterns in Arabidopsis thaliana.
Altered glycosylation of exported proteins, including surface immune receptors, compromises calcium and downstream signaling responses to microbe-associated molecular patterns in Arabidopsis thaliana.
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DOI：
10.1186/s12870-016-0718-3
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发表时间：
2016-01-28
影响因子：
5.3
通讯作者：
Lee J
中科院分区：
文献类型：
--
作者：
Trempel F;Kajiura H;Ranf S;Grimmer J;Westphal L;Zipfel C;Scheel D;Fujiyama K;Lee J
钙作为第二信使，将细胞外信号转导到细胞反应中。细胞质钙离子浓度的上升是植物暴露于微生物相关分子模式（MAMPs）后的第一反应之一。我们先前报道了分离拟南芥突变体的“改变钙升高”（cce）flg 22，一个22-氨基酸的MAMP来自细菌鞭毛蛋白的反应。在这里，我们的特点cce 2突变体和它的较弱的等位基因突变体，cce 3。除了flg 22之外，突变体对几种其他MAMP和植物内源性肽的钙升高降低，所述植物内源性肽在创伤期间由前原蛋白质进行蛋白水解加工。下游防御相关事件，如flg 22诱导的丝裂原活化蛋白激酶活化，活性氧的积累和生长停滞也在cce 2/cce 3中减弱。通过基因定位、新一代测序和等位性分析，将CCE 2/CCE 3鉴定为ALG 3（Asparagine-linked glycosylation 3）。编码α-1，3-甘露糖基转移酶，负责内质网（ER）腔侧核心寡糖Glc 3 Man 9 GlcNAc 2聚糖组装的第一步。酵母alg 3突变体中的互补测定和聚糖分析证实了由cce 2/cce 3等位基因编码的蛋白质的酶功能降低-导致M5 ER的积累，M5 ER是在ER中发现的不成熟的含五甘露糖的寡糖结构。适当的蛋白质糖基化是ER/高尔基体加工和膜蛋白向质膜运输所必需的。在cce 2/cce 3突变体中，flg 22受体FLS 2的糖苷内切酶H不敏感性表明受体中的聚糖结构改变。MAMP受体（或其他输出蛋白）的适当糖基化是对MAMP的最佳应答所必需的，并且对于宿主植物的免疫信号传导是重要的。本文的在线版本（doi：10.1186/s12870-016-0718-3）包含补充材料，可供授权用户使用。
Calcium, as a second messenger, transduces extracellular signals into cellular reactions. A rise in cytosolic calcium concentration is one of the first plant responses after exposure to microbe-associated molecular patterns (MAMPs). We reported previously the isolation of Arabidopsis thaliana mutants with a “changed calcium elevation” (cce) response to flg22, a 22-amino-acid MAMP derived from bacterial flagellin. Here, we characterized the cce2 mutant and its weaker allelic mutant, cce3. Besides flg22, the mutants respond with a reduced calcium elevation to several other MAMPs and a plant endogenous peptide that is proteolytically processed from pre-pro-proteins during wounding. Downstream defense-related events such flg22-induced mitogen-activated protein kinase activation, accumulation of reactive oxygen species and growth arrest are also attenuated in cce2/cce3. By genetic mapping, next-generation sequencing and allelism assay, CCE2/CCE3 was identified to be ALG3 (Asparagine-linked glycosylation 3). This encodes the α-1,3-mannosyltransferase responsible for the first step of core oligosaccharide Glc3Man9GlcNAc2 glycan assembly on the endoplasmic reticulum (ER) luminal side. Complementation assays and glycan analysis in yeast alg3 mutant confirmed the reduced enzymatic function of the proteins encoded by the cce2/cce3 alleles – leading to accumulation of M5ER, the immature five mannose-containing oligosaccharide structure found in the ER. Proper protein glycosylation is required for ER/Golgi processing and trafficking of membrane proteins to the plasma membrane. Endoglycosidase H-insensitivity of flg22 receptor, FLS2, in the cce2/cce3 mutants suggests altered glycan structures in the receptor. Proper glycosylation of MAMP receptors (or other exported proteins) is required for optimal responses to MAMPs and is important for immune signaling of host plants. The online version of this article (doi:10.1186/s12870-016-0718-3) contains supplementary material, which is available to authorized users.