Analysis of symbiotic mineral nutrient transport and mechanisms underlying regulation of the arbuscular mycorrhizal (AM) symbiosis

80%以上的维管束开花植物能够与丛枝菌根真菌形成共生共生关系。这些组合在根中发展，在那里真菌共生体将磷和氮从土壤转移到植物中，以换取碳。在共生中，AM真菌栖息在根皮质细胞中，在那里它们形成被称为丛枝的分枝菌丝。丛枝负责将养分输送到根细胞。以往对紫花苜蓿的研究表明，一种共生特异性的磷酸盐转运蛋白MtPT4对于共生磷酸盐的运输是必不可少的。在这个项目中，研究人员将进一步分析MtPT4，此外，还将开始表征第二个磷酸盐转运体MtPT8和新的铵转运体MtAMT2的作用。缺乏这些转运蛋白的单株、双株和三株突变植株将被用来确定共生磷和氮运输在多大程度上调节AM共生。实验将解决潜在的机制和涉及的信号通路。该项目的第二个方面侧重于共生中的蛋白质靶向。MtPT4蛋白专门位于一种特殊的膜上，称为丛生膜，它包裹着丛生植物。使用免疫学方法和标记有荧光蛋白的MtPT4的活细胞成像，研究人员将分析蛋白质靶向茎周膜的机制。AM共生几乎由所有维管束开花植物形成，但调节共生磷和铵运输的蛋白质、调节关键共生界面维持的机制以及将调控机制与植物的矿质营养状态相结合的信号通路在很大程度上都是未知的。这些实验中产生的数据将促进我们对共生的这些方面的理解。该项目包括为本科生提供获得共焦显微镜经验的机会。

Over 80% of the vascular flowering plants are capable of forming mutualistic symbioses with arbuscular mycorrhizal (AM) fungi. These associations develop in the roots, where in exchange for carbon, the fungal symbionts transfer phosphorus and nitrogen from the soil to the plant. In the symbiosis, the AM fungi inhabit the root cortical cells where they form branched hyphae called arbuscules. The arbuscules are responsible for nutrient delivery to the root cells. Previous studies in Medicago truncatula indicated that a symbiosis-specific phosphate transporter, MtPT4, is essential for symbiotic phosphate transport. In this project the investigators will further analyze MtPT4 and in addition, begin to characterize the roles of a second phosphate transporter, MtPT8, and a novel ammonium transporter, MtAMT2. Single, double and triple mutant plants lacking these transporters will be generated and they will be used to determine the extent to which symbiotic phosphate and nitrogen transport regulate the AM symbiosis. Experiments will address the underlying mechanisms and signaling pathways involved. A second aspect of the project focuses on protein targeting in the symbiosis. The MtPT4 protein is located exclusively on a specialized membrane called the peri-arbuscular membrane, which surrounds the arbuscule. Using immunological approaches, and live cell imaging of MtPT4 tagged with fluorescent proteins, the investigators will analyze the mechanisms underlying protein targeting to the peri-arbuscular membrane. The AM symbiosis is formed by almost all vascular flowering plants but the proteins that mediate symbiotic phosphate and ammonium transport, the mechanisms that regulate maintenance of key symbiotic interfaces, and the signaling pathways that integrate regulatory mechanisms with the mineral nutrient status of the plant, are all largely unknown. The data generated in these experiments will advance our understanding of these aspects of the symbiosis. The project includes opportunities for undergraduate students to obtain experience with confocal microscopy.