EAGER: RUI: The Physiology and Nitrogen Assimilatory Pathway of Spanish Moss (Tillandsia Usneoides) in Pesponse to Increased Nitrogen

西班牙苔藓(Tillandsia Usneides)是美国东南部一种生长缓慢的无根植物，常见于树木上，如活橡树。由于它们不在土壤中扎根，这些“空气植物”必须从大气和降雨中获得营养。因此，与其他植物相比，它们的环境营养极其贫乏。这个项目调查了西班牙苔藓对氮含量增加的反应，氮是最常限制植物生长的营养物质。与其他植物相比，西班牙苔藓的含氮量明显较低，这提出了一个植物学谜团：西班牙苔藓是如何在氮如此稀缺的环境中生存的？实验旨在确定西班牙苔藓是否真的是氮素受限的，或者更确切地说，这些植物是否进化出了一种独特的能力，可以有效地利用有限的氮素。了解西班牙苔藓在氮素有限的情况下是如何存活的，可以为寻求在边缘化土壤上提高作物产量的植物育种者提供洞察力。此外，由于气候变化预计会增加大气中氮的沉积，这些实验可能会揭示西班牙苔藓未来的生长模式。这项研究包括对卡罗莱纳海岸大学和国家聋人技术学院的本科生进行现代科学技术培训，加强他们的教育和未来科学劳动力的多样性。这个假说驱动的项目的中心目标是提供证据，证明增加的氮素供应是否通过刺激氮素同化途径来促进附生植物西班牙苔藓的生长。生化、代谢和生理学方法将被用来回答两个关键问题：(I)西班牙苔藓是否表现出奢侈的氮素消耗；(Ii)这些植物是否受到氮素限制，或者更确切地说，它们是否表现出高氮素利用效率？该项目将通过添加和处理生理上相关的浓度来操纵硝酸盐和铵的输入。氮同化途径的响应将通过测量硝酸还原酶和谷氨酰胺合成酶活性、氨基酸和蛋白质浓度以及氨基酸生物合成来评估。重要的是，它将决定无机氮流入从头生成氨基酸的流量增加是否与增长相结合。此外，实验将测量硝酸还原酶--植物氮素同化中的限速酶--的动力学，并确定它如何受到硝酸盐和铵的有效性的调节。西班牙苔藓与南方的文化和身份密切相关，但人们对它们如何代谢氮一无所知。该项目将是第一个调查这些植物中氮素代谢的项目，并确定增加的氮素可获得性和同化是否与生长有关。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Spanish moss (Tillandsia usneoides) is a slow-growing rootless plant in the Southeastern United States that is often found on trees, such as live oak. Since they don’t have roots in the soil, these “air plants” must acquire nutrients from the atmosphere and from rainfall. Therefore, their environment is extremely nutrient poor compared to other plants. This project investigates how Spanish moss responds to increased amounts of nitrogen, the nutrient that most often restricts plant growth. Nitrogen content in Spanish moss is remarkably lower compared to other plants, which presents a botanical mystery: how does Spanish moss survive in an environment where nitrogen is so scarce? Experiments are designed to determine if Spanish moss is truly nitrogen-limited or rather if these plants have evolved a unique ability to efficiently use limited nitrogen. Understanding how Spanish moss survives despite limited nitrogen could provide insight to plant breeders who seek to improve crop yield on marginalized soils. Additionally, because climate change is predicted to increase atmospheric deposition of nitrogen, these experiments might reveal future growth patterns of Spanish moss. The study includes training of undergraduates from Coastal Carolina University and the National Technical Institute for the Deaf in modern scientific techniques, enhancing their education and the diversity of the future scientific workforce. The central goal of this hypothesis-driven project is to provide evidence if increased nitrogen availability supports enhanced growth of the epiphyte Spanish moss by stimulating the nitrogen assimilation pathway. Biochemical, metabolomic, and physiological approaches will be used to answer two key questions: (i) does Spanish moss display nitrogen luxury consumption and (ii) are these plants nitrogen limited or rather do they display high nitrogen use efficiency? The project will manipulate nitrate and ammonium inputs by both spiking and treating with a physiologically relevant concentrations. The response of the nitrogen assimilation pathway will be assessed by measuring nitrate reductase and glutamine synthetase activity, amino acid and protein concentration, and amino acid biosynthesis. Importantly it will determine if increased flux of inorganic nitrogen into de novo amino acids is coupled with growth. Additionally, experiments will measure the kinetics of nitrate reductase- a rate limiting enzyme in plant nitrogen assimilation- and determine how it is regulated by nitrate and ammonium availability. Spanish moss is tightly tied to southern culture and identity, yet nothing is known about how they metabolize nitrogen. This project will be the first to investigate nitrogen metabolism in these plants, and to determine if increased nitrogen availability and assimilation is coupled to growth.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.