RESEARCH-PGR: Sieve Tube Proteomics - Unraveling the Physiology and Cell Biology of an Arcane Cell Type

人类消耗的食物是通过植物的光合作用直接产生的（比如土豆）或间接产生的（比如食草动物的肉）。光合作用发生在植物的绿色部分，但是，除了莴苣等例外，饥饿的人类对谷物、块茎和水果等植物的非光合作用储存器官更感兴趣。植物将光合作用的产物（从化学上讲是糖）通过韧皮部组织中的微小管道网络，即所谓的筛管，将其从绿色部分转移到储存器官。由于其极端的敏感性，活筛管的功能是出了名的难以研究，我们对筛管运输及其调控的理解仍然非常差。这是不幸的，特别是因为许多韧皮部吸吮害虫，如蚜虫，利用筛管中源源不断的富含能量的物质。更糟糕的是，许多致病病毒和细菌搭乘这条河流，从一个单一的切入点开始，侵扰整个植物。由于这些因素每年都会造成大量的作物损失，韧皮部在植物性能中的关键功能转化为经济意义，这一点很难被夸大。本研究将为了解筛管作用的基本机制，为设计防治病虫害的措施做出重要贡献。可能参与筛管生理的蛋白质将通过大规模的生化方法（“蛋白质组学”）进行鉴定，然后通过对编码它们的基因进行定向修饰，逐一进一步分析。在更广泛的影响方面，该项目将通过一个艺术展览吸引公众的兴趣，其中包括在普尔曼/莫斯科地区机场航站楼展示的韧皮部细胞的大幅面照片，并将继续更新“韧皮部”网页。此外，PI将与华盛顿州立大学多元文化学生服务办公室合作，招募少数民族本科生到实验室工作。血管系统允许生物体通过大量流动在内部分配资源，从而克服扩散造成的尺寸限制。包括筛管在内的维管组织的发展推动了大型陆地植物（管生植物）的进化，导致陆地生态系统生产力的显著提高。这种生产力支持着地球上各种形式的生命。最大的光自养海洋生物，海带，已经逐渐进化出运输筛管，突出了这种运输和通信系统对大型光合和无根生命形式的重要性。本项目旨在阐明筛管细胞生物学和生理学的开放性问题。最先进的蛋白质组学方法将通过比较维管组织和分离筛元件的蛋白质组学来识别可能参与运输调节的蛋白质。候选蛋白将通过其编码基因的修饰进行荧光标记，并确定蛋白质在运输管中的亚细胞定位。先进的生物成像工具将应用于将筛管蛋白质分配到特定的细胞器或膜系统，生成筛管细胞器相互作用的3D模型，并表征蛋白质分布对压力的反应。所获得的见解有望为培育更健壮和抗虫害的作物提供重要信息。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。

The food consumed by humans is produced in plants by photosynthesis, either directly (think of potatoes) or indirectly (meat from plant-eating animals). Photosynthesis occurs in the green parts of plants, but, with exceptions such as lettuce, hungry humans are more interested in non-photosynthesizing storage organs of plants including grain, tubers, and fruits. Plants transfer the products of photosynthesis (sugars, chemically speaking) from their green parts to storage organs via a network of microscopic pipes, the so-called sieve tubes, in the phloem tissue. Due to their extreme sensitivity, the function of live sieve tubes is notoriously hard to study, and our understanding of sieve tube transport and its regulation has remained lamentably poor. This is unfortunate, especially since numerous phloem-sucking pests, for instance aphids, exploit the continuous stream of energy-rich substances in the sieve tubes. What often is worse are the many pathogenic viruses and bacteria that hitch rides in this stream to infest the entire plant, starting from a single point of entry. As these factors cause massive crop losses every year, the critical function of phloem in plant performance translates into an economic significance that can hardly be overstated. This project will make important contributions to comprehension of fundamental mechanisms of sieve tube function, which will facilitate the design of treatments and preventive measures targeting pests and pathogens. Proteins potentially involved in sieve tube physiology will be identified by a large-scale biochemical approach (‘proteomics’), and then further analyzed one by one through directed modification of the genes that encode them. With regard to Broader Impacts, the project will engage public interest with an artistic exhibition that incorporates large format photographs of phloem cells displayed in the terminal of the Pullman/Moscow regional airport and will also continue updating a “Phloem” webpage. In addition the PI will work with the Office of Multicultural Student Services at Washington State University to recruit minority undergraduate students to work in the lab.Vascular systems allow organisms to distribute resources internally by bulk flow, thus overcoming size limitations set by diffusion. The development of vascular tissues including sieve tubes drove the evolution of large land plants (tracheophytes) which caused a major increase in the productivity of terrestrial ecosystems. This productivity supports life on earth in its various forms. The largest photoautotroph marine organisms, kelps, have convergently evolved transporting sieve tubes, highlighting the significance of this transport and communication system for large photosynthetic and sessile life forms. This project aims at elucidating open questions in the cell biology and physiology of sieve tubes. State-of-the-art proteomics approaches will be applied to identify proteins potentially involved in transport regulation, by comparing the proteomes of vascular tissue and isolated sieve elements. Candidate proteins will be fluorescently tagged by modifications of their encoding genes, and the subcellular localization of the proteins in transporting tubes will be determined. Advanced bioimaging tools will be applied to assign sieve tube proteins to specific organelles or membrane systems, to generate 3D models of sieve tube organelle interactions, and to characterize the responses of protein distribution to stress. The insights gained are expected to provide essential information for the generation of more robust and pest-resistant crops.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.