脱落酸（ABA）调节丛枝菌根系统抗旱性机理研究

Arbuscular mycorrhiza (AM), a ubiquitous symbiotic association established between AM fungi and roots of higher plants in most terrestrial ecosystems, is essentially important for host plant adaptation to drought stress. However, so far limited information is available as for the mechanisms underlying the synergetic drought resistance of AM symbiosis and the signaling between the symbiotic partners. In the proposed project, wild type A17 of Medicago truncatula and an AM fungus Rhizophagus irregularis DAOM 197198 are adopted to establish in vitro culture of AM fungi. ABA responding proteins in AM fungi will be identified by host-induced gene silencing and heterologous expression in yeast. In combination with suppression subtractive hybridization and non-invasive ion-selective microelectrode technique, ABA signaling pathway in AM fungi as activated by exogenous ABA will be verified. Based on previous work, compartment cultivation experiment will be performed with ABA defective plant mutant as test plant, with the assistance of a laser microdissection system, to identify signal transduction between host plant and associated AM fungi under drought stress. As a result, the regulatory mechanisms of ABA stimulation of the synergetic drought resistance of AM symbiosis will be illustrated. The study is expected to lay a solid foundation for further research into molecular basis for the stress signaling pathway between AM fungi and host plants.

丛枝菌根（arbuscular mycorrhiza, AM）在宿主植物抵御干旱胁迫中起着非常关键的作用。然而，目前关于AM真菌与宿主植物之间的协同抗旱机制知之甚少，尤其是干旱胁迫下共生体系的逆境信号交流途径相关基础研究还鲜有报道。本申请项目以蒺藜苜蓿野生型A17为试验材料，通过构建AM真菌双重无菌培养系统，利用异源表达和宿主植物诱导的基因沉默技术，明确AM真菌中脱落酸（ABA）响应蛋白，同时结合抑制消减杂交和非损伤微测技术，阐明外源ABA驱动下的AM真菌ABA信号通路；在此基础上，结合植物ABA突变体和分室试验，并利用激光显微切割技术获得的丛枝界面，研究干旱胁迫条件下联系AM真菌和宿主植物的信号转导途径，阐明ABA在增强菌根共生体系统抗旱性方面的调控机制。预期本项目的实施可系统揭示菌根共生伙伴之间对胁迫信号因子ABA的响应机制，可望实质性推动菌根共生体逆境信号交换机制研究。

丛枝菌根（arbuscular mycorrhiza，AM）对于植物适应各种逆境胁迫具有重要积极作用。然而，目前对于干旱胁迫下菌根共生体建立以及AM真菌和宿主植物之间信号交流的认识极其有限。本研究以AM真菌水孔蛋白GintAQPF2为例，通过对其进行功能验证，探讨GintAQPF2结构特征对菌根共生体建成的意义。采用分根培养系统，探讨干旱胁迫下AM真菌和宿主植物之间的信号交流途径和菌根共生体系协同抗旱机制。研究结果表明GintAQPF2 ar/R结构域的特殊特征对于控制甘油跨膜运输和AM共生体系建成具有重要意义。分根试验结果显示植物中ABA信号途径中两个关键功能基因，肌醇-3-磷酸合酶基因IPS和14-3-3蛋白基因14-3GF的共表达能够启动AM真菌对植物抗旱性的系统调控以及宿主植物和AM真菌间的信号交流，这对于实现AM共生体的协同抗旱至关重要。.在AM真菌双重无菌培养体系中，我们进一步考察了聚乙二醇（polyethylene glycol, PEG）模拟干旱胁迫和外源ABA处理下AM根外菌丝中离子转运蛋白基因表达的变化。试验结果表明PEG处理显著上调了AM根外菌丝中氢离子、钙离子和硝酸根离子转运蛋白基因的表达；ABA处理也显著上调了根外菌丝中氢离子转运蛋白基因的表达，但显著下调了钙离子转运蛋白基因的表达，表明AM真菌抗旱调节机制与ABA信号途径有一定联系。进一步的转录组学分析表明PEG主要改变了菌丝P450代谢过程，而ABA促进了AM真菌菌丝中糖酵解过程，抑制了氨基糖和核糖的代谢过程，从而增强了真菌的抗逆能力。