Spatiotemporal plasticity of carbon allocation and rhizodeposition in the maize root system and its impact on the rhizosphere microbiome

植物在地下转移相当一部分最近固定的碳(RFC)来建立根结构并为根的功能提供能量。除此之外，植物来源的碳为根际微生物的生命提供了燃料。然而，目前对根构型、RFC分配和根际微生物群之间的时空关系知之甚少。在这个项目的第一阶段，我们发现了RFC在根系统中的时空分配模式。RFC在根尖积累最强，特别是在最近出现的冠根尖。根际微生物群落组成对这些模式作出了响应，但对根型的影响更大。根C分配随根类型的变化及其作为微生物组结构和功能驱动因素的时间动态的潜在原因需要进一步研究。在这个后续项目中，我们建议通过引入土壤异质性(即土壤紧实层)来获得根和根际过程之间的机理理解，并由此挑战根的可塑性。我们假设局部干扰引起了根的生长和RFC分配的变化，从而对根际微生物群产生了影响。我们将应用磁共振成像和正电子发射断层扫描相结合的方法，对根部性状进行非侵入性的4D量化和RFC分配。通过RNA-SIP标记13CO2后，将跟踪RFC向根际的转移和微生物(细菌、真菌、原生生物)的掺入。为了全面了解动态反应，我们将通过根转录和根际转译来补充我们的方法。这将提供一个关于改变RFC分配对微生物根际过程的原因和后果的整体看法。因此，我们的项目将提供关于根际自组织时空模式发展的基本原理的重要知识，这对于从机制上理解植物的表现是相关的。

Plants transfer a substantial part of recently fixed carbon (RFC) belowground to build up root structure and to provide energy for root functions. Beyond that, plant derived C fuels microbial life in the rhizosphere. However, spatiotemporal relationships between root architecture, RFC allocation and the rhizosphere microbiome are currently little understood. In the first phase of this project we found spatiotemporal allocation patterns of RFC within the root system. RFC accumulated strongest at root tips and in particular at the most recently emerged crown root tips. Microbial community composition in the rhizosphere responded to these patterns, though more strongly to root types. The underlying causes of variation in root C allocation in dependence on root type and its temporal dynamics as drivers for microbiome structure and function need further investigations. In this follow up project, we propose to gain mechanistic understanding between root and rhizosphere processes by introducing soil heterogeneity (i.e. a soil compaction layer) and therewith challenge root plasticity. We hypothesize that local disturbance introduces changes in root growth and allocation of RFC with consequences on the rhizosphere microbiome. We will apply Magnetic Resonance Imaging in combination with Positron Emission Tomography for non-invasive 4D quantification of root traits and RFC allocation. Transfer of RFC into the rhizosphere and its incorporation by microorganisms (bacteria, fungi, protists) will be tracked after 13CO2 labelling by RNA-SIP. For a comprehensive understanding of the dynamic responses, we will complement our approach by root transcriptomics and rhizosphere metatranscriptomics. This will provide a holistic view on the causes and consequences of altered RFC allocation on microbial rhizosphere processes. Our project will thus provide significant knowledge about principles underlying the development of self-organized spatiotemporal patterns in the rhizosphere, which is relevant for a mechanistic understanding of plant performance.