Cytosolic activation of cell death and stem rust resistance by cereal MLA-family CC-NLR proteins
Cytosolic activation of cell death and stem rust resistance by cereal MLA-family CC-NLR proteins
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DOI：
10.1073/pnas.1605483113
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发表时间：
2016-09-06
影响因子：
11.1
通讯作者：
Dodds, Peter N.
中科院分区：
文献类型：
--
作者：
Cesari, Stella;Moore, John;Dodds, Peter N.
植物具有称为“核苷酸结合结构域和富含亮氨酸重复序列”（NLR）蛋白的细胞内免疫受体，其将病原体特异性识别转化为抗病信号。小麦免疫受体Sr33和Sr50属于卷曲螺旋（CC）NLR类。它们赋予对小麦叶锈菌（Puccinia graminis f.）小麦白粉病抗性蛋白MLA10是大麦白粉病抗性蛋白MLA10的同源物。在这里，我们表明，类似于MLA10，Sr33和Sr50 CC结构域足以诱导本氏烟草细胞死亡。自激活CC结构域和全长Sr33和Sr50蛋白在植物中自缔合。相比之下，截短的CC结构域的大小相当于一个MLA10片段，其晶体结构是以前确定的不能诱导细胞死亡，不自缔合。在截短区域的突变也消除了自我关联和细胞死亡信号。分析与YFP融合的Sr33和Sr50 CC结构域以及N. Benthamiana表明细胞死亡诱导发生在胞质溶胶中。在稳定的转基因小麦植物中，全长Sr33蛋白靶向的细胞质提供抗锈性，而核靶向Sr33是没有功能的。这些数据与CC介导的诱导细胞死亡信号传导和细胞质隔室中的茎锈病抗性一致，而先前的研究表明MLA 10介导的细胞死亡和抗病性信号传导分别独立地发生在细胞质和细胞核中。
Plants possess intracellular immune receptors designated "nucleotide-binding domain and leucine-rich repeat" (NLR) proteins that translate pathogen-specific recognition into disease-resistance signaling. The wheat immune receptors Sr33 and Sr50 belong to the class of coiled-coil (CC) NLRs. They confer resistance against a broad spectrum of field isolates of Puccinia graminis f. sp. tritici, including the Ug99 lineage, and are homologs of the barley powdery mildew-resistance protein MLA10. Here, we show that, similarly to MLA10, the Sr33 and Sr50 CC domains are sufficient to induce cell death in Nicotiana benthamiana. Autoactive CC domains and full-length Sr33 and Sr50 proteins self-associate in planta. In contrast, truncated CC domains equivalent in size to an MLA10 fragment for which a crystal structure was previously determined fail to induce cell death and do not self-associate. Mutations in the truncated region also abolish self-association and cell-death signaling. Analysis of Sr33 and Sr50 CC domains fused to YFP and either nuclear localization or nuclear export signals in N. benthamiana showed that cell-death induction occurs in the cytosol. In stable transgenic wheat plants, full-length Sr33 proteins targeted to the cytosol provided rust resistance, whereas nuclear-targeted Sr33 was not functional. These data are consistent with CC-mediated induction of both cell-death signaling and stem rust resistance in the cytosolic compartment, whereas previous research had suggested that MLA10-mediated cell-death and disease resistance signaling occur independently, in the cytosol and nucleus, respectively.