Expression profiling during arabidopsis/downy mildew interaction reveals a highly-expressed effector that attenuates responses to salicylic acid.
Expression profiling during arabidopsis/downy mildew interaction reveals a highly-expressed effector that attenuates responses to salicylic acid.
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DOI：
10.1371/journal.ppat.1004443
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发表时间：
2014-10
期刊：
影响因子：
6.7
通讯作者：
Jones JD
中科院分区：
文献类型：
--
作者：
Asai S;Rallapalli G;Piquerez SJ;Caillaud MC;Furzer OJ;Ishaque N;Wirthmueller L;Fabro G;Shirasu K;Jones JD
植物已经进化出强大的先天免疫机制，但成功的病原体通过将效应器传递到植物细胞中来逃避或抑制植物免疫。拟南芥透明operonospora Arabidopsis （Hpa）引起霜霉病，并获得了分离株Emoy2的基因组序列。在这里，我们利用Hpa和拟南芥基因组序列的可用性来同时测量Hpa和拟南芥在感染过程中的基因表达变化。利用高通量cDNA标签测序方法，我们揭示了Hpa预测效应子和拟南芥基因在相容和不相容相互作用中的表达模式，以及与Hpa基因相关的启动子在感染过程中的表达。通过对Hpa分离物Waco9进行重测序，我们发现它通过删除同源的已知效应物ATR1来逃避拟南芥抗性基因RPP1。拟南芥水杨酸（SA）应答基因包括PR1不仅在不亲和互作的早期被激活，而且在亲和互作的后期也被激活。通过组织化学分析，我们发现Hpa抑制sa诱导的PR1表达，特别是在宿主易位效应物被递送到的吸噬细胞中，但在非吸噬邻近细胞中没有。最后，我们发现了一种高表达的Hpa效应候选物，可以抑制对SA的反应。由于这种方法可以很容易地应用于宿主和病原体基因组序列可用的宿主-病原体相互作用，这项工作为感染生物学的转录组研究打开了大门，这应该有助于揭示病原体感染策略和宿主防御反应被克服的机制。全面了解宿主-病原体相互作用需要了解宿主和病原体在感染时间过程中基因表达变化的动态。然而，由于涉及微阵列的方法的限制，表达谱分析通常集中在宿主或病原体上。本文采用高通量RNA测序方法报道了拟南芥及其寄生虫拟南芥透明膜孢子虫（Hpa）在感染过程中基因表达的变化。通过对Hpa分离物Waco9的重测序，我们发现它通过删除同源的识别效应物ATR1来逃避拟南芥抗性基因RPP1。我们还发现，在宿主易位效应物被递送的吸胞中，Hpa抑制对水杨酸（SA）的反应。一种Hpa效应物HaRxL62在本实验中被高度表达，之前被证明可以增强宿主的敏感性，我们发现它抑制了对SA的反应。病原体效应基因和宿主基因参与免疫的表达谱使我们能够提出不同的效应介导的易感性机制，并揭示有趣的Hpa效应，以便在未来的实验中进行详细的机制研究。
Plants have evolved strong innate immunity mechanisms, but successful pathogens evade or suppress plant immunity via effectors delivered into the plant cell. Hyaloperonospora arabidopsidis (Hpa) causes downy mildew on Arabidopsis thaliana, and a genome sequence is available for isolate Emoy2. Here, we exploit the availability of genome sequences for Hpa and Arabidopsis to measure gene-expression changes in both Hpa and Arabidopsis simultaneously during infection. Using a high-throughput cDNA tag sequencing method, we reveal expression patterns of Hpa predicted effectors and Arabidopsis genes in compatible and incompatible interactions, and promoter elements associated with Hpa genes expressed during infection. By resequencing Hpa isolate Waco9, we found it evades Arabidopsis resistance gene RPP1 through deletion of the cognate recognized effector ATR1. Arabidopsis salicylic acid (SA)-responsive genes including PR1 were activated not only at early time points in the incompatible interaction but also at late time points in the compatible interaction. By histochemical analysis, we found that Hpa suppresses SA-inducible PR1 expression, specifically in the haustoriated cells into which host-translocated effectors are delivered, but not in non-haustoriated adjacent cells. Finally, we found a highly-expressed Hpa effector candidate that suppresses responsiveness to SA. As this approach can be easily applied to host-pathogen interactions for which both host and pathogen genome sequences are available, this work opens the door towards transcriptome studies in infection biology that should help unravel pathogen infection strategies and the mechanisms by which host defense responses are overcome. A comprehensive understanding of host-pathogen interactions requires knowledge of the dynamics of gene expression changes in both the host and the pathogen during a time course of infection. However, expression profiling has often focused on either the host or the pathogen due to limitations of methods that involve microarrays. We report here gene expression changes in both Arabidopsis and its parasite Hyaloperonospora arabidopsidis (Hpa) simultaneously during infection using a high-throughput RNA sequencing method. By resequencing Hpa isolate Waco9, we found it evades Arabidopsis resistance gene RPP1 through deletion of cognate recognized effector ATR1. We also found that Hpa suppresses responsiveness to salicylic acid (SA) in haustoriated cells into which host-translocated effectors are delivered. An Hpa effector HaRxL62, previously shown to enhance host susceptibility, was highly expressed in this assay, and we found it suppresses responsiveness to SA. Expression profiling of both pathogen effector genes and host genes involved in immunity allows us to suggest distinct mechanisms of effector-mediated susceptibility and reveals interesting Hpa effectors for detailed mechanistic investigation in future experiments.