Probing the molecular interactions at the extrahaustorial membrane interface

面对气候变化和人口增长，粮食安全是人类面临的重大挑战；然而，在全球范围内，每年因病原体而损失的作物高达15%。保护作物免受病原体侵害是一项关键的、持续的全球倡议。许多重要的农业疾病是由白粉病和锈病真菌以及真菌样卵菌病原体引起的。这些进化上截然不同的病原体的一个共同特征是，它们发展出类似的取食结构，称为吸器，以入侵植物并从宿主细胞中提取营养。尽管在了解植物抵抗病原体的分子机制方面取得了巨大进展，但寄主防御如何在植物-吸器界面中执行仍然知之甚少。该研究旨在利用模型病理系统和最先进的遗传学和生物化学工具，识别和功能表征宿主-病原体界面称为吸器外膜的新分子参与者。该项目的新发现不仅有助于更好地了解宿主-病原体界面的分子组成，而且有助于设计新的策略来对抗吸器形成的病原体，减少作物损失，从而为可持续农业做出贡献。吸器形成的病原体，如白粉病真菌，在宿主组织中形成一种称为吸器的摄食结构，分泌能够抑制宿主免疫反应并从宿主细胞中提取营养物质的效应蛋白。吸器与宿主细胞通过宿主衍生的界面膜——吸器外膜（EHM）进行物理分离。EHM被认为是宿主-病原体最关键的战场，在这里，宿主的防御被安装来限制吸器，病原体部署效应物来破坏宿主的免疫并从宿主中提取营养。然而，尽管EHM很重要，但其分子成分和与宿主防御或发病机制相关的机制尚不清楚。该项目的长期目标是了解EHM的蛋白质组成以及植物-吸器在宿主-病原体界面上的相互作用机制。将拟南芥-白粉病相互作用作为模型病理系统，并将RPW8.2（一种广谱抗性蛋白）作为第一个也是最好的EHM特异性驻留蛋白，一个合作团队将(i)通过基于接近度的标记，结合吸体复合物的富集/纯化，以及质谱分析，鉴定和表征与EHM中RPW8.2相互作用的蛋白和其他EHM驻留蛋白；（ii）解析RPW8.2的蛋白质结构，了解RPW8.2的ehm取向的囊泡运输是如何由Trans-Golgi网络中的候选SNARE复合物调控的；（iii）确定寄主的易感因子，如糖转运体，这些因子可能被白粉病真菌招募到EHM中，通过遗传和细胞生物学方法获取营养。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Food security is a grand challenge facing humanity in the face of climate change and population growth; yet, on a global scale up to 15% of crops are lost to pathogens each year. Protecting crops from pathogens is a critical, ongoing global initiative. Many agriculturally important diseases are caused by powdery mildew and rust fungi, and fungus-like oomycete pathogens. One common feature of these evolutionarily distinct pathogens is that they develop similar feeding structures called haustoria to invade plants and extract nutrients from host cells. Despite tremendous progress towards understanding the molecular mechanisms of plant resistance against pathogens, how the host defense is executed in the plant-haustorial interface is still poorly characterized. The research aims to identify and functionally characterize novel molecular players at the host-pathogen interface termed the extrahaustorial membrane using a model pathosystem and state-of-the-art genetics and biochemistry tools. New findings from this project will not only lead to a better understanding of the molecular composition of the host-pathogen interface but also help design novel strategies to fight against haustorium-forming pathogens and reduce crop losses, thereby contributing to sustainable agriculture. Haustorium-forming pathogens such as powdery mildew fungi develop a feeding structure termed the haustorium in host tissues to secrete effector proteins capable of suppressing the host immune response and extracting nutrients from the host cell. The haustorium is physically separated from the host cell by a host-derived interfacial membrane named the extrahaustorial membrane (EHM). The EHM is believed to be the most critical host-pathogen battleground, where the host defense is mounted to constrain the haustorium, and the pathogen deploys effectors to subvert host immunity and extracts nutrients from the host. However, despite the importance of the EHM, its molecular components and the mechanisms associated with host defense or pathogenesis are poorly characterized. The long term goal of this project is to understand the protein composition of the EHM and the mechanisms of plant-haustorium interactions at this host-pathogen interface. Using the Arabidopsis-powdery mildew interaction as a model pathosystem and RPW8.2 (a broad-spectrum resistance protein) as the first and best EHM-specific resident protein, a collaborative team will (i) identify and characterize proteins interacting with RPW8.2 at the EHM and additional EHM-resident proteins via proximity-based labeling coupled with enrichment/purification of haustorial complexes followed by mass spectrometry; (ii) resolve the protein structure of RPW8.2 and understand how EHM-oriented vesicle transport of RPW8.2 is regulated by a candidate SNARE complex at the Trans-Golgi Network; and (iii) identify host susceptibility factors, such as sugar transporters, which may be recruited to the EHM by powdery mildew fungi for nutrient acquisition through both genetic and cell biological approaches.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.