The Role of a Membrane Channel in Conferring Fluoride Resistance in Plants

氟化物是地壳中含量第13多的元素。自然和工业来源造成土壤、水和空气中的氟化物含量。虽然对氟化物没有生物需求，但低浓度的氟化物可以提高动物牙齿的质量。然而，在某些条件下，氟化物是有毒的。毒性取决于多种因素，包括浓度、暴露时间和生物体本身。对氟敏感的植物，如剑兰，在20 ppm （1 mM）的浓度下受到伤害，而超过1200 ppm （63 mM）的浓度对耐氟茶树没有明显的影响。单细胞生物对氟化物毒性的保护是通过称为FEX（氟化物出口）的膜通道从细胞中去除氟离子来实现的。最近在包括植物在内的多细胞生物中发现了一种编码这种氟化物通道的基因。植物特别容易受到氟化物的影响，因为它们暴露在土壤、水和空气中的氟化物中。此外，用于促进植物生长的磷肥是污染氟化物的来源，因为它们是由含有氟化物的磷矿生产的。研究植物中假定的氟化物通道将拓宽我们对它们如何避免氟化物毒性的理解。这一知识将有助于保护作物免受氟化物的侵害，并可能降低特定植物组织中氟化物的浓度。在与耶鲁大学科学之路项目的合作下，初高中学生将通过全天的节日、深入的研讨会和广泛的暑期实验室体验来探索植物生物学和科学方法。本研究探讨了FEX对植物耐氟性的影响。在酵母FEX基因敲除中，对几种植物的氟离子通道进行了测试，发现其对氟的耐受性与天然酵母FEX相似。此外，在正常植物生长条件下，拟南芥中FEX的缺失是致命的。各种活力和生长试验将被用来评估FEX水平改变对植物的影响。FEX如何影响氟化物在植物中的传播将使用18F和正电子发射断层扫描（PET）进行监测。此外，将使用细胞特异性启动子操纵FEX的表达，以确定植物是否采用或将受益于协调的高阶氟化物调节策略。这项工作将确定工厂如何积累和消散氟化物以及FEX在这一过程中的作用。将获得关于如何使用FEX改善氟化物解毒的信息。这是对多细胞生物中FEX和氟化物外排的首次研究。这些实验将深入了解FEX通过差异调节将氟化物引导到特定组织或从特定组织中进出的能力，为植物氟化物毒性的表征创造基线，并为氟化物解毒和生物修复开辟新的研究领域。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。

Fluoride is the 13th-most abundant element in the Earth’s crust. Natural and industrial sources contribute to fluoride levels in the soil, water, and air. While there is no biological requirement for fluoride, low concentrations of fluoride enhance teeth quality in animals. However, under certain conditions, fluoride is toxic. Toxicity depends on multiple factors including concentration, exposure time, and the organism itself. Fluoride-sensitive plants like Gladiolus are injured at a concentration of 20 ppm (1 mM), while concentrations above 1200 ppm (63 mM) have no observable effects on the fluoride-tolerant tea plant. Protection against fluoride toxicity in single-celled organisms is achieved by removing fluoride ions from the cell through a membrane channel called FEX (Fluoride Exporter). A gene encoding this fluoride channel has been recently identified in multicellular organisms, including plants. Plants are particularly vulnerable to fluoride because they are exposed to fluoride from the soil, water, and air. In addition, phosphate fertilizers used to enhance plant growth are sources of contaminating fluoride because they are produced from rock phosphate, which contains fluoride. Studying the putative fluoride channel in plants will broaden our understanding of how they avoid fluoride toxicity. This knowledge will help to protect crop plants from fluoride and possibly reduce the concentration of fluoride in specific plant tissues. In cooperation with the Yale Pathways to Science program, middle- and high- school students will explore plant biology and the scientific method through an all-day festival, in-depth workshops, and extensive summer laboratory experiences. This research investigates how FEX contributes to fluoride tolerance in plants. Putative fluoride channels from several plants have been tested in a yeast FEX knockout and found to provide fluoride tolerance to a level similar to native yeast FEX. In addition, deletion of FEX in Arabidopsis is lethal in normal plant growth conditions. A variety of viability and growth assays will be used to assess the effect of altered levels of FEX in plants. How FEX affects fluoride travels through plants will be monitored using 18F and Positron Emission Tomography (PET). Additionally, the expression of FEX will be manipulated using cell-specific promoters to ascertain whether plants employ, or would benefit from, a coordinated higher-order strategy for fluoride regulation. This work will establish how the plant accumulates and dissipates fluoride and the role of FEX in that process. Information will be obtained on how to improve fluoride detoxification using FEX. It represents the first study of FEX and fluoride efflux in a multicellular organism. These experiments will provide insights into the ability of FEX to direct fluoride to or from specific tissues through differential regulation, create a baseline for characterization of fluoride toxicity in plants, and open up new areas of study for fluoride detoxification and bioremediation.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.