Plant microbiome manipulation: nitrogen as the key currency

氮有效性是限制陆地生态系统生长的主要因素。不加选择地使用氮肥是绿色革命提高产量的关键。然而，氮肥现在是农业面临的环境和经济问题的前沿。鉴于其有限性，我假设对氮的竞争是调节植物-微生物在土壤-根界面相互作用的中心机制。我收集的初步数据表明，植物通过在根际分泌微rna （miRNAs）有意抑制细菌的氨基酸渗透酶基因表达。这将导致大部分土壤氨基酸库被输送到植物中。此外，我已经证明，氨氧化剂在决定小麦产量和谷物品质方面起着关键作用，其作用远远超过施肥量。氨氧化剂是细菌和古细菌，它们将氨转化为硝酸盐，以产生能量，用于固定二氧化碳（化学合成）。因此，它们完全不依赖植物提供的碳，但它们需要肥料或有机氮降解产生的氨来满足它们的能量需求。同时，氨在能量上比硝酸盐更有利于植物生长，使植物和氨氧化剂的需求针锋相对。我的研究计划旨在1)理解和展示氮在植物与微生物相互作用中的关键作用，包括有机和无机氮源，以及2)寻找利用氮修饰植物与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mirna在根际氮竞争中的作用；2)确定氨基酸在根际氮竞争中的作用；3)通过改变对氮的竞争来操纵植物微生物组。我的研究计划将提供对植物-微生物相互作用规则的深入理解。导致新的方法来塑造植物微生物群朝着作物产量和质量的优化。创新性实验与测序、生物信息学、多元统计等先进的分子方法相结合，将为我的项目培养3名博士、3名硕士和10名本科生，使他们成为行业、政府或学术界的核心人物。

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.