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.

我们研究了两种分子机制，植物可以保护自己免受病毒的侵害。 RNA沉默包含许多相关过程，这些过程通过识别和处理双链RNA来调节内源基因的基因表达以及外核酸。大多数植物病毒会产生双链RNA复制中间体，这些中间体可以由宿主RNA沉默机制靶向。 DICER蛋白在定义的小RNA中进行双链RNA处理，而这些RNA又受靶标和切割互补的单链RNA的Argonaute（AGO）内核酸酶约束。同时，植物病毒编码抑制剂或RNA沉默（VSR），干扰RNA沉默机制。我们已经开发了一个功能和遗传测定的平台，以分析拟南芥和其他物种的AGO蛋白质的抗病毒活性。在此过程中，我们已经确定了靶向病毒RNA的三种AGO2，AGO4和AGO5的三种关键蛋白。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，它们具有使它们可以访问病毒RNA的特性，该病毒RNA通常受到病毒复制复合物的保护。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蛋白如何靶向病毒RNA以及病毒如何抵消这种防御。此外，我们将研究自然变异在AGO蛋白质中的作用，在确定病毒宿主范围，其在植物健身中的作用以及其在开发耐病毒抗药性植物中的效用。我们还研究一种称为效应介导的免疫（ETI）的先天免疫力，该免疫力是由免疫受体样蛋白（NB-LRR蛋白）介导的，该蛋白（NB-LRR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套件。我们已经表明，ETI信号导致病毒mRNA翻译的抑制。此外，尽管ETI并未引起全局抑制蛋白质翻译，但使用翻译方法，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。我们将表征抑制病毒翻译的机制和因素，并表征ETI防御反应期间翻译调节的转录本的参与。此外，我们将表征全球翻译调节器在有效病原体防御所必需的生长到防御转变中的作用。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。