Molecular mechanisms of plant defense against pathogens / Mécanismes moléculaires de défense des plantes contre les pathogènes

植物防御病原体的分子机制 / Mäcanismes moläculaires de däfense des plantes contre les Pathogànes

• 批准号: RGPIN-2017-05438
• 负责人: Moffett, Peter
• 金额: $ 5.03万
• 依托单位: Université de Sherbrooke
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=745025
• 关键词: Molecular; mechanisms; plant; defense; against

We study two molecular mechanisms by which plants defend themselves against viruses. RNA silencing encompasses a number of related processes that regulate gene expression of endogenous genes, as well as foreign nucleic acids, through the recognition and processing of double-stranded RNA. Most plant viruses produce double-stranded RNA replication intermediates that can be targeted by the host RNA silencing machinery. Dicer proteins process double-stranded RNAs into defined small RNAs and these in turn are bound by Argonaute (AGO) endoribonucleases that target and cleave complementary single-stranded RNA. At the same time, plant viruses encode suppressors or RNA silencing (VSRs), which interfere with the RNA silencing machinery. We have developed a platform of functional and genetic assays to analyse the antiviral activities of AGO proteins from Arabidopsis thaliana and other species. In doing so, we have identified three key proteins, AGO2, AGO4 and AGO5 that target viral RNAs. In particular, we find that these proteins not only overcome VSR activity, but, unlike other members of the AGO family, they possess properties that allow them to access viral RNA, which is normally protected inside viral replication complexes. We will undertake structure-function, cell biological and genetic analyses to understand how certain AGO proteins are able to target viral RNAs and how viruses counteract this defense. In addition, we will study the role of natural variation in AGO proteins in determining virus host range, its role in plant fitness and its utility in developing virus-resistant plants. We also study a type of innate immunity known as effector-mediated immunity (ETI) that is mediated by immune receptor-like proteins (NB-LRR proteins) that recognize all types of pathogens and induce a dramatic suite of defence responses. We have shown that ETI signaling leads to an inhibition of viral mRNA translation. In addition, although ETI does not cause a global inhibition of protein translation, using a translatomic approach, we find that large numbers of transcripts have altered translational status during ETI signaling. We will characterize the mechanisms and factors that inhibit viral translation as well as characterizing the involvement of translationally regulated transcripts during ETI defense responses. In addition, we will characterize the role of the global translational regulator TOR in the growth-to-defense transition that is necessary for effective pathogen defense. These approaches will employ a variety of plant model systems, genetics, biochemistry, cell and molecular biology.

我们研究植物防御病毒的两种分子机制。 RNA沉默包含许多相关过程，通过双链RNA的识别和加工来调节内源基因以及外源核酸的基因表达。大多数植物病毒产生双链RNA复制中间体，可以被宿主RNA沉默机制靶向。 Dicer 蛋白将双链 RNA 加工成特定的小 RNA，而这些小 RNA 又与 Argonaute (AGO) 核糖核酸内切酶结合，该酶靶向并切割互补的单链 RNA。同时，植物病毒编码抑制子或RNA沉默（VSR），它会干扰RNA沉默机制。我们开发了一个功能和遗传检测平台来分析拟南芥和其他物种的 AGO 蛋白的抗病毒活性。在此过程中，我们鉴定出了三种针对病毒 RNA 的关键蛋白：AGO2、AGO4 和 AGO5。特别是，我们发现这些蛋白质不仅克服了 VSR 活性，而且与 AGO 家族的其他成员不同，它们具有允许它们访问病毒 RNA 的特性，而病毒 RNA 通常在病毒复制复合物内受到保护。我们将进行结构功能、细胞生物学和遗传分析，以了解某些 AGO 蛋白如何能够靶向病毒 RNA 以及病毒如何抵消这种防御。此外，我们将研究 AGO 蛋白的自然变异在确定病毒宿主范围中的作用、其在植物适应性中的作用及其在开发抗病毒植物中的效用。我们还研究了一种称为效应介导免疫（ETI）的先天免疫，它由免疫受体样蛋白（NB-LRR 蛋白）介导，可识别所有类型的病原体并诱导一系列引人注目的防御反应。我们已经证明 ETI 信号传导会抑制病毒 mRNA 翻译。此外，虽然ETI不会导致蛋白质翻译的整体抑制，但使用翻译组学方法，我们发现大量转录本在ETI信号传导过程中改变了翻译状态。我们将描述抑制病毒翻译的机制和因素，以及描述 ETI 防御反应期间翻译调节转录本的参与。此外，我们将描述全局翻译调节因子 TOR 在生长到防御转变中的作用，这对于有效的病原体防御是必要的。这些方法将采用各种植物模型系统、遗传学、生物化学、细胞和分子生物学。