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

植物将相当一部分近期固定碳（RFC）转移到地下，以建立根系结构并为根系功能提供能量。除此之外，植物衍生的碳为根际微生物的生命提供燃料。然而，根构型、RFC分配与根际微生物群之间的时空关系目前尚不清楚。在该项目的第一阶段，我们发现了根系中RFC的时空分配模式。RFC在根尖积聚最强，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有响应，但对根类型的响应更强烈。根系C分配随根系类型变化的根本原因及其作为微生物组结构和功能驱动因素的时间动态需要进一步研究。在这个后续项目中，我们建议通过引入土壤异质性（即土壤压实层）来获得根和根际过程之间的机制理解，从而挑战根的可塑性。我们假设，局部干扰导致了根生长和RFC分配的变化，并对根际微生物群产生了影响。我们将利用磁共振成像与正电子发射断层成像相结合的方法对根系性状进行无创四维量化和RFC分配。RFC向根际的转移及其通过微生物（细菌、真菌、原生生物）的结合将在RNA-SIP标记13CO2后进行跟踪。为了全面了解动态响应，我们将通过根转录组学和根际元转录组学来补充我们的方法。这将提供一个整体的观点，改变RFC分配对微生物根际过程的原因和后果。因此，我们的项目将提供有关根际自组织时空模式发展原理的重要知识，这与植物性能的机制理解有关。

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.