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

80%以上的维管开花植物能与丛枝菌根真菌形成互惠共生。这些关联在根部发展，在那里交换碳，真菌共生体将磷和氮从土壤转移到植物中。在共生中，AM真菌栖息在根皮层细胞中，在那里它们形成称为丛枝的分支菌丝。丛枝负责向根细胞输送养分。先前在蒺藜苜蓿中的研究表明，共生特异性磷酸盐转运蛋白MtPT 4是共生磷酸盐转运所必需的。在该项目中，研究人员将进一步分析MtPT 4，此外，开始表征第二种磷酸盐转运蛋白MtPT 8和新型铵转运蛋白MtAMT2的作用。将产生缺乏这些转运蛋白的单突变体、双突变体和三突变体植物，并且它们将用于确定共生磷酸盐和氮转运调节AM共生的程度。实验将解决相关的潜在机制和信号通路。该项目的第二个方面侧重于共生中的蛋白质靶向。MtPT4蛋白仅位于一种称为丛枝周围膜的专门膜上，该膜围绕着丛枝。使用免疫学方法和荧光蛋白标记的MtPT4的活细胞成像，研究人员将分析蛋白质靶向血管周围膜的机制。AM共生是由几乎所有的维管开花植物形成的，但是介导共生磷酸盐和铵运输的蛋白质，调节关键共生界面的维持的机制，以及将调节机制与植物的矿物质营养状态整合的信号通路，在很大程度上都是未知的。在这些实验中产生的数据将促进我们对共生关系的这些方面的理解。该项目包括为本科生获得共聚焦显微镜的经验的机会。

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.