Chemical signaling in mycorrhizal symbiosome development in Lotus japonicus

该项目的重点是丛枝菌根（AM）真菌和豆科植物百脉根之间的化学和分子相互作用在AM共生的后期发展阶段，即在共生体的形成，这是双向交换的营养物质和代谢物发生的地方。在菌根植物中，AM真菌和宿主植物以正磷酸盐（Pi）形式跨质膜吸收磷是由膜内真菌和植物Pi转运蛋白介导的。与直接从土壤溶液中吸收磷的贡献相比，菌根磷吸收途径几乎可以完全支配植物对磷的吸收。这一途径调控的分子基础仍然知之甚少。因此，该项目的主要目标是表征参与触发菌根特异性Pi转运蛋白基因表达的植物和/或真菌化学信号。基于质谱的技术的使用已经有助于识别AM Pi运输中的第一个脂质信号，并且对于识别和进一步表征AM共生中的信号分子是该项目的核心。2011年，申请人的实验室将配备应用生物系统（ABI Sciex）QTRAP 5500与NanoMate系统耦合，用于直接输注脂质样品，这将允许深入分析菌根脂质提取物，并通过nanoESI-MS/MS鉴定通过质量峰发现的磷脂化合物。基于脂质和转录谱的综合比较方法将使探索植物和真菌脂质代谢的分子基础AM共生。本项目的第二部分旨在阐明植物磷转运蛋白基因在AM共生体形成过程中的转录调控的进化保守机制。植物和其他植物物种。这包括继续我们的工作，确定顺式和反式作用因子指导各自AM特异性基因的启动子活性。在这里，总体目标是表征许多基因的协调表达是建立AM共生体所必需的。

The proposed project focuses on the chemical and molecular interaction between arbuscular mycorrhizal (AM) fungi and the legume Lotus japonicus in late developmental stages of the AM symbiosis, i.e. during formation of the symbiosome which is the site where bi-directional exchange of nutrients and metabolites takes place. In mycorrhizal plants, P uptake in the form of orthophosphate (Pi) across the plasma membrane of AM fungus and host plant is mediated by membrane intrinsic fungal and plant Pi transporter proteins. The contribution of the mycorrhizal Pi uptake pathway compared to that of direct Pi uptake from the soil solution can dominate total plant P uptake almost completely. The molecular basis of this pathway’s regulation is still poorly understood. A primary goal of this project is therefore to characterize plant and/or fungal chemical signal(s) which are involved in triggering mycorrhiza-specific Pi transporter gene expression. The use of mass spectrometry based technologies has been instrumental to identify the first lipid signal in AM Pi transport and is central to this project for identification and further characterization of signal molecules in the AM symbiosis. In 2011, the applicant’s laboratory will be equipped with an Applied Biosystems (ABI Sciex) QTRAP 5500 coupled to a NanoMate system for direct infusion of lipid samples which will allow in depth analysis of mycorrhizal lipid extracts and identification of phospholipid compounds discovered via their mass peaks through nanoESI-MS/MS. An integrated comparative approach based on lipid and transcript profiling will enable exploration of the molecular basis of plant and fungal lipid metabolism underlying AM symbiosis. The second part of this project, aims at unravelling the evolutionary conserved mechanisms underlying transcriptional regulation of plant Pi transporter genes during formation of the AM symbiosome in L. japonicus and other plant species. This includes a continuation of our work on the identification of cis- and trans-acting factors directing promoter activity of respective AM-specific genes. Here, the overall goal is to characterize the many genes the coordinated expression of which is required to build an AM symbiosome.