根际真菌提高甘草水分和磷利用率的生理机制研究

Water shortage and phosphorus deficiency are important factors in restricting plant growth. Rhizosphere microorganisms can dissolve phosphate and induce stomatal closure in order to decrease water loss. However, so far few studies have used rhizosphere microorganisms - soil - plant stomata relationships to improve stress resistance under both drought and low phosphorus stresses. This project will use yeast, Metarhizium anisopliae and licorice to observe the dose-effect relationship and temporal dynamics of stomatal closure induced by rhizosphere fungi; and explore their signal transduction mechanisms during stomatal closure regulated by root-sourced signals (e.g. ABA) induced by rhizosphere fungi and effectors; and use photosynthesis parameters, chlorophyll fluorescence parameters, effective constituents of licorice and yield to observe how rhizosphere fungi regulate water and nutrient physiological ecology, and improve both quality and yield of licorice by affecting stomatal movements and activating inorganic phosphorus under both drought and low phosphorus stresses. In this study, our researches will reveal the physiological and ecological mechanisms for improving water use efficiency (WUE) by rhizosphere fungi regulated stomatal behavior, and demonstrate that rhizosphere fungi can enhance WUE by improved availability of soil fertilizer, then improve drought resistance, which provide good understanding of microbe - soil - plant interactions, and it is important for developing water-saving agriculture and enhancing the level of Chinese herbal medicine industry.

水资源短缺和土壤磷匮乏是制约植物生长的重要因素。根际微生物可以溶解固态磷且能诱使气孔关闭从而减少植物水分散失。但在干旱和低磷双重胁迫下，利用根际微生物-土壤-植物气孔的关系提高植物抗逆性的研究相对滞后。本项目以酵母、金龟子绿僵菌和甘草为研究对象，观察根际真菌诱发气孔关闭的剂量效应和时间动态，探索根际真菌及其激发子类物质通过脱落酸（ABA）等根源信号诱导气孔关闭的信号转导机制；以光合作用、叶绿素荧光参数、药材有效成分和产量等为主要指标，揭示干旱低磷条件下，根际真菌如何通过影响气孔运动及活化无机磷调控甘草的水分和养分生理生态，提高甘草药材品质和产量。该研究旨在阐释根际真菌调控气孔行为以提高甘草水分利用效率的生理生态机制，论证根际微生物溶解固态磷“以肥调水”提高甘草抗旱性，为理解微生物-土壤-植物之间复杂的关系提供一定的理论基础，对发展高效节水农业和提升中药材产业水平有重要意义。

植物生长在复杂的自然环境中，与有益微生物，如根际促生菌等共存。为了缓解环境胁迫造成的压力，植物与共生有益微生物已经演化出一系列互利互惠的生存机制。本项目通过室内盆栽控制实验，探讨了酵母、金龟子绿僵菌对植物生理生态的影响。得到以下结论：（1）甘草转录组结果显示，干旱处理显著影响氧化还原酶活动、膜组成部分、蛋白激酶等相关过程和功能的基因表达。KEGG代谢通路富集分析发现富集的前3位代谢通路分别是转运蛋白、转录因子和蛋白激酶；（2）在正常条件下及干旱和低磷双重胁迫下，根际实施金龟子绿僵菌后能显著促进植物生长，提高株高、根长、生物量、叶面积、根体积等指标，叶绿素和N素含量明显升高，这说明根际促生菌有可能通过促进植物对营养元素的吸收，帮助植物抵御非生物胁迫；（3）药理学实验证明金龟子绿僵菌能通过Ca2+第二信使，NO信号，水通道蛋白和ROS爆发有效诱导气孔关闭；（4）酵母、金龟子绿僵菌均能影响植物光合作用参数，提高植物的水分利用效率，改善抗旱能力。本项目阐释了根际微生物提高甘草水分利用效率的生理生态机制，为农业生产的抗旱节水措施提供新思路。