A molecular perspective on plant-microbiome interactions during rhizosphere development

根际的自组织产生了多方面的化学梯度，其中植物-微生物的相互作用是一个关键的驱动力。土壤溶液是根际的重要组成部分，在根生长和引入植物来源的碳后，有机分子的化学梯度首先在根际形成。土壤类型、环境因素、植物基因型、微生物群落等都驱动着土壤溶液的化学演变。一个发展中的根际新出现的化学和生物模式反映了这些驱动因素之间复杂的相互作用和反馈回路。该提案旨在调查从土柱实验的非根际先决条件开始的早期根际发育中有机碳小尺度分子梯度的时空发展，这些实验完全嵌入优先方案的中央平台实验。微型吸盘土壤溶液采样和超高分辨率质谱（FTICR-MS）分析有机质组成将是主要工具。我们的主要假设是，在根际土壤溶液分子梯度的收敛演化主要是由微生物的快速周转根源碳。为此，我们将使用两个玉米基因型（野生型和rth 3突变体）生长在土柱配备微型吸盘，生物测定和稳定同位素标记，以跟踪释放的有机分子的根，这些转化的微生物群落和映射的空间范围和动态的根际。FTICR-MS为土壤溶液中的完整分子提供了最高的“化学分辨率”，而微型吸盘能够以高时间分辨率对根际中最动态的土壤室及其碳库进行采样。除此之外，我们还将开发分子成像方法，在保留分子化学信息的同时扩展空间分辨率。这种新颖独特的根际研究工具组合将使我们对碳通量的理解远远超出大宗预算，并有助于确定发展中根际的重要驱动因素，并评估其对化学梯度的影响。以前所未有的细节研究土壤溶液化学的时空动态将为根际的自组织和恢复力提供有价值的见解，将有助于更好地了解不同的土壤过程如何塑造根际的化学组成和多样性，将缩小根系分泌物，土壤化学和微生物生态学重点研究之间的知识差距，并将特别有助于PP的系统方法。因此，我们的提案直接与土壤中碳获取和周转相关的项目（例如启动，封存），微生物生态学和群落动态以及应用化学成像和稳定同位素方法的项目相互作用和联系。

Self-organization in the rhizosphere generates multi-faceted chemical gradients in which the plant-microbe interplay is a key driver. The soil solution is a crucial component of the rhizosphere, where chemical gradients of organic molecules first develop upon growth of roots and introduction of plant-derived carbon. Soil type, environmental factors, plant genotype, microbial community, etc. then all drive the chemical evolution of the soil solution. Emerging chemical and biological pattern of a developing rhizosphere reflect the complex interactions and feed-back loops between these drivers. This proposal aims at investigating the spatio-temporal development of small-scale molecular gradients of organic carbon in early rhizosphere development from non-rhizosphere pre-conditions in soil column experiments which are fully embedded into the central platform experiments of the priority programme (PP). Micro suction cups for soil solution sampling and ultrahigh-resolution mass spectrometry (FTICR-MS) to analyze the organic matter composition will be the major tools. Our key hypothesis is that the convergent evolution of soil solution molecular gradients in the rhizosphere is mainly driven by rapid microbial turnover of root derived carbon. To this end, we will use two Zea mays genotypes (wildtype and rth3 mutant) grown in soil columns equipped with micro suction cups, bioassays and stable isotope labels to track the release of organic molecules by roots, the transformation of these by the microbial community and to map the spatial extent and dynamics of the rhizosphere. FTICR-MS provides the highest possible “chemical resolution” for intact molecules in soil solution while micro suction cups are able to sample the most dynamic soil compartment and its carbon pool in the rhizosphere at a high temporal resolution. Beyond that, we will also develop molecular imaging methods, extending the spatial resolution while conserving molecular chemical information. This novel and unique combination of state-of-the-art tools in rhizosphere research will expand our understanding of carbon fluxes far beyond a bulk budget and help to identify important drivers in a developing rhizosphere and assess their impact on chemical gradients.Studying the spatio-temporal dynamics of soil solution chemistry in unprecedented detail will give valuable insights into the self-organization and resilience of the rhizosphere, will help to better understand how distinct soil processes shape the chemical composition and diversity of the rhizosphere, will close the knowledge gap between root exudate, soil chemistry and microbial ecology focused research, and will notably contribute to the systems approach of the PP. Our proposal thus directly interacts with and connects to projects related to carbon acquisition and turnover in soils (e.g. priming, sequestration), to microbial ecology and community dynamics as well as projects applying chemical imaging and stable isotope methods.