Plant microbiome manipulation: nitrogen as the key currency

氮素有效性是限制陆地生态系统生长的主要因素。不分青红皂白地使用氮肥是绿色革命带来的增产的核心。然而，氮肥目前处于农业面临的环境和经济问题的前沿。鉴于其限制性的性质，我假设对N的竞争是调节土壤-根界面上植物-微生物相互作用的中心机制。我收集的初步数据表明，该植物通过分泌其根际的microRNAs(MiRNAs)来强烈地抑制细菌的氨基酸渗透酶基因的表达。这将导致土壤氨基酸库的更大部分被输送到植物。此外，我已经证明，氨氧化剂在决定小麦产量和谷物质量方面发挥着关键作用，远远超过了化肥的施用量。氨氧化菌是细菌和古细菌，它们将氨转化为硝酸盐，以便产生能量，用来固定二氧化碳(化学合成)。因此，它们完全独立于工厂提供的碳，但它们需要化肥中的氨或有机氮的降解来满足其能量需求。同时，氨在能量上比硝酸盐更有利于植物的生长，将植物和氨氧化剂的需求放在一起。我的研究计划旨在1)了解和论证氮在植物-微生物相互作用中的关键作用，无论是有机氮源还是无机氮源，以及2)寻找利用氮素改善植物-微生物相互作用的新方法。更具体地说，我的短期目标是：1)确定植物miRNAs在根际N的竞争中的作用；2)确定氨基酸在根际N的竞争中的作用；3)通过改变N的竞争来操纵植物微生物群。我的研究计划将提供对植物-微生物相互作用规则的高级理解，导致形成植物微生物区系的新方法，以实现作物产量和质量的优化。创新实验与测序、生物信息学和多元统计等先进的分子方法相结合，将为我的项目中的3名博士生、3名硕士学生和10名本科生做好准备，使他们能够在行业、政府或学术界担任核心职位。

Nitrogen (N) availability is the main factor limiting growth in terrestrial ecosystems. Indiscriminate use of nitrogen fertilization was central to the yield boost brought by the Green Revolution. However, N fertilization is now at the forefront of the environmental and economical issues facing agriculture. In view of its limiting nature, I hypothesize that competition for N is a central mechanism regulating plant-microbe interactions at the soil-root interface. I have gathered preliminary data that show that the plant intendedly inhibits the amino acid permease gene expression of bacteria through the secretion of micro RNAs (miRNAs) in its rhizosphere. This would result in a larger part of the soil amino acid pool being routed to the plant. Additionally, I have shown that ammonia-oxidizers have a key role in determining wheat yields and grain quality, much more than the amount of applied fertilizer. Ammonia oxidizers are bacteria and archaea that transform ammonia to nitrate in order to generate energy that they use to fix carbon dioxide (chemosynthesis). As such, they are completely independent from the carbon provided by the plant, but they need ammonia from fertilizer or from the degradation of organic nitrogen to fulfill their energy requirement. At the same time, ammonia is energetically more favorable for plant growth than nitrate, putting the needs of the plant and of the ammonia-oxidizers head-to-head. My research program aims at 1) understanding and demonstrating the key role of nitrogen in plant-microbe interactions, both for organic and inorganic nitrogen sources, and 2) finding novel ways to modify plant-microbe interactions using nitrogen. More specifically, my short-term objectives are to 1) Determine the role of plant miRNAs in the competition for N in the rhizosphere, 2) Determine the role of amino acids in the competition for N in the rhizosphere and 3) Manipulate the plant microbiome by changing the competition for N. My research program will provide an advanced understanding of the rules governing plant-microbe interactions, leading to novel approaches to shape the plant microbiota toward an optimization of crop yields and quality. The combination of innovative experiments combined with advanced molecular methods such as sequencing, bioinformatics and multivariate statistics will prepare the 3 PhD students, 3 MSc students and 10 undergraduate students involved in my program to take up central positions in the industry, the government or academia.