Anti-viral mechanisms induced by the plant immune system / Les mécanismes anti-viraux induits par le système immunitaire végétal

我们研究植物抵御病原体，特别是病毒的分子机制。针对植物病毒的主要防御之一是以病毒的RNA遗传物质为靶标。一种被广泛称为RNA沉默的机制存在于所有真核生物中，它识别双链RNA，并负责调节多种生物过程，包括通过靶向病毒双链RNA降解来产生病毒抗性。DICER蛋白质将双链RNA加工成确定的小RNA，这些小RNA又被结合到“切片器”复合体中，这些复合体针对任何与小RNA互补的RNA。切片器复合体的活性成分是一类被称为精氨酸(AGO)蛋白的内切核酸酶家族。高等植物基因组编码至少十年前的蛋白质，这些蛋白质参与了与RNA沉默相关的各种现象，其中一些参与了结构性的抗病毒防御。反过来，植物病毒进化出了RNA沉默的抑制子，以克服这种结构性防御。然而，除了RNA沉默，植物还编码免疫受体样蛋白(NB-LRR蛋白)，这些蛋白识别所有类型的病原体，并诱导一系列戏剧性的防御反应。我们发现，NB-LRR蛋白与某些AGO蛋白结合，阻止病毒RNA翻译蛋白质，从而阻止病毒的传播。然而，这一过程似乎使用了不同的AGOS家族成员，而不是那些参与结构性抗病毒反应的成员。我们将确定哪些AGO家族成员负责结构性和诱导性抗病毒反应，并将使用各种植物模型系统、遗传学、生物化学、细胞和分子生物学来表征这些蛋白质如何影响病毒RNA转录本的翻译。此外，我们将鉴定与Nb-LRR蛋白相互作用的细胞蛋白，以便更深入地了解诱导的抗病毒反应是如何启动的。

We study the molecular mechanisms by which plants defend themselves against pathogens in general, and viruses in particular. One of the main defences against plant viruses is based on targeting the RNA genetic material of the virus. A mechanism broadly known as RNA silencing exists in all eukaryotes that recognizes double-stranded RNAs and is responsible for regulating multiple biological processes, including virus resistance by targeting viral double-stranded RNA for degradation. Dicer proteins process double-stranded RNAs into defined small RNAs and these in turn are incorporated into "slicer" complexes which target any RNAs with complementarity to the small RNA. The active components of slicer complexes are a family of endoribonucleases known as Argonaute (AGO) proteins. Higher plant genomes encode at least ten AGO proteins, which are involved in a variety of RNA silencing-related phenomenon, and some of these have been implicated in constitutive anti-viral defences. In turn, plant viruses have evolved suppressors of RNA silencing to overcome this constitutive defence. However, in addition to RNA silencing, plants encode immune receptor-like proteins (NB-LRR proteins) that recognize all types of pathogens and induce a dramatic suite of defence responses. We have found that NB-LRR proteins engage certain AGO proteins to occlude viral RNAs from translating protein, hence stopping the virus from spreading. However, this process appears to use different AGOs family members than those involved in constitutive anti-viral responses. We will identify which AGO family members are responsible for both constitutive and induced anti-viral responses and we will characterize how these proteins affect the translation of viral RNA transcripts using a variety of plant model systems, genetics, biochemistry, cell and molecular biology. In addition we will identify cellular proteins that interact with NB-LRR proteins in order to gain more insight into how induced anti-viral responses are initiated.