The cysteine rich necrotrophic effector SnTox1 produced by Stagonospora nodorum triggers susceptibility of wheat lines harboring Snn1.
The cysteine rich necrotrophic effector SnTox1 produced by Stagonospora nodorum triggers susceptibility of wheat lines harboring Snn1.
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DOI：
10.1371/journal.ppat.1002467
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发表时间：
2012-01
期刊：
影响因子：
6.7
通讯作者：
Friesen TL
中科院分区：
文献类型：
--
作者：
Liu Z;Zhang Z;Faris JD;Oliver RP;Syme R;McDonald MC;McDonald BA;Solomon PS;Lu S;Shelver WL;Xu S;Friesen TL
小麦病原体Stagonospora nodorum产生多种坏死营养效应物（也称为宿主选择性毒素），其通过与相应的宿主敏感性基因产物相互作用来促进疾病。SnTox 1是在S. nodorum，并显示出诱导携带Snn 1的小麦品系坏死。在这里，我们报告的SnTox 1的分子克隆和验证，以及SnTox 1-Snn 1相互作用，导致易感性的机制的初步表征。利用生物信息学工具对SnTox 1进行了鉴定，并通过在毕赤酵母中的异源表达进行了验证。SnTox 1编码一个117个氨基酸的蛋白质，前17个氨基酸被预测为信号肽，并且引人注目的是，成熟蛋白含有16个半胱氨酸残基，这是一些无毒效应物的共同特征。将SnTox 1转化到无毒的S. nodorum分离物足以使菌株致病。此外，缺失的SnTox 1在有毒的菌株呈现SnTox 1突变株无毒的Snn 1差异小麦线。SnTox 1存在于全球85%的S.根瘤菌分离物。我们确定了总共11种蛋白质亚型，并发现了对SnTox 1进行强多样性选择的证据。SnTox 1-Snn 1相互作用导致氧化爆发、DNA梯状化和发病相关（PR）基因表达，所有这些都是防御反应的标志。在没有光的情况下，SnTox 1诱导的坏死和疾病症状的发展被完全阻断。通过比较GFP标记的无毒分离物和SnTox 1转化的相同分离物的感染过程，我们得出结论，SnTox 1可能在真菌渗透过程中发挥关键作用。这项研究进一步表明，坏死营养型真菌病原体利用小的效应蛋白来利用植物抗性途径进行定殖，这为小麦-S的分子基础提供了重要的见解。nodorum相互作用，一个新兴的模式necrotrophic病理系统。在这份手稿中，我们描述了SnTox 1从Stagonospora nodorum，编码的第一个主机选择性毒素（SnTox 1）在这种真菌中确定的基因的克隆。SnTox 1诱导坏死和促进疾病的小麦品系携带Snn 1基因。我们通过在酵母培养物中表达SnTox 1基因来验证其功能，其中所得培养物滤液诱导坏死，但仅在携带功能性Snn 1的小麦品系上。将SnTox 1基因转化到无毒的S. nodorum分离物，从而产生对含有Snn 1的小麦品系有毒的分离物。SnTox 1在S. nodorum分离物，从而消除Snn 1差异小麦品系上的病害。此外，我们研究了宿主对SnTox 1和S. nodorum菌株产生SnTox 1，并发现在敏感反应期间存在抗性反应的几个标志，表明坏死营养型病原体S. nodorum可能利用SnTox 1刺激涉及Snn 1的宿主抗性途径来诱导疾病。
The wheat pathogen Stagonospora nodorum produces multiple necrotrophic effectors (also called host-selective toxins) that promote disease by interacting with corresponding host sensitivity gene products. SnTox1 was the first necrotrophic effector identified in S. nodorum, and was shown to induce necrosis on wheat lines carrying Snn1. Here, we report the molecular cloning and validation of SnTox1 as well as the preliminary characterization of the mechanism underlying the SnTox1-Snn1 interaction which leads to susceptibility. SnTox1 was identified using bioinformatics tools and verified by heterologous expression in Pichia pastoris. SnTox1 encodes a 117 amino acid protein with the first 17 amino acids predicted as a signal peptide, and strikingly, the mature protein contains 16 cysteine residues, a common feature for some avirulence effectors. The transformation of SnTox1 into an avirulent S. nodorum isolate was sufficient to make the strain pathogenic. Additionally, the deletion of SnTox1 in virulent isolates rendered the SnTox1 mutated strains avirulent on the Snn1 differential wheat line. SnTox1 was present in 85% of a global collection of S. nodorum isolates. We identified a total of 11 protein isoforms and found evidence for strong diversifying selection operating on SnTox1. The SnTox1-Snn1 interaction results in an oxidative burst, DNA laddering, and pathogenesis related (PR) gene expression, all hallmarks of a defense response. In the absence of light, the development of SnTox1-induced necrosis and disease symptoms were completely blocked. By comparing the infection processes of a GFP-tagged avirulent isolate and the same isolate transformed with SnTox1, we conclude that SnTox1 may play a critical role during fungal penetration. This research further demonstrates that necrotrophic fungal pathogens utilize small effector proteins to exploit plant resistance pathways for their colonization, which provides important insights into the molecular basis of the wheat-S. nodorum interaction, an emerging model for necrotrophic pathosystems. In this manuscript we describe the cloning of SnTox1 from Stagonospora nodorum, the gene encoding the first host selective toxin (SnTox1) identified in this fungus. SnTox1 induces necrosis and promotes disease on wheat lines harboring the Snn1 gene. We verified the function of the SnTox1 gene by expressing it in a yeast culture where the resulting culture filtrate induced necrosis but only on wheat lines that carried a functional Snn1. The SnTox1 gene was also transformed into an avirulent S. nodorum isolate, resulting in an isolate that was virulent on wheat lines harboring Snn1. SnTox1 was also disrupted in virulent S. nodorum isolates resulting in the elimination of disease on Snn1 differential wheat lines. Additionally, we investigated the host response to SnTox1 and S. nodorum strains producing SnTox1 and discovered that several hallmarks of a resistance response were present during the susceptible reaction, showing that the necrotrophic pathogen S. nodorum is likely using SnTox1 to stimulate a host resistance pathway involving Snn1 to induce disease.
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