Spatiotemporal organization of the rhizosphere microbiome shaped by external drivers

根际微生物群对土壤生态系统功能和植物生长健康具有重要作用。根际的自组织产生于根、微生物和土壤之间的反馈循环。在SPP2089的第一阶段，我们的目标是揭开影响根际微生物群落空间和时间格局的主要外部驱动因素。通过中央土柱试验和田间小区试验，研究了两个玉米品种(野生型(WT)和根毛缺陷突变体(RT3))在两种不同土壤基质(壤土(L)和沙土(S))中根际微生物群落的变化。对总群落(TC)-DNA的16S rRNA基因及其扩增产物的序列分析表明，土壤基质对玉米根际微生物群落的影响最大，其次是土壤深度和玉米基因型(SCE和SPE)。出乎意料的是，玉米根毛的存在对姐妹染色单体交换和固相萃取中的根际微生物群的影响很小。在第二阶段，我们将继续更详细地讨论SPP2089的假设1和4以及新的问题II、III和IV，以揭示玉米根际微生物群落的空间组织取决于土壤质地和外部驱动因素的存在(接种有益微生物[BMS]、干旱条件)。我们将参加在实验室(SCE_DARISH)和野外(SPE_BBCH19)尺度上进行的中心实验，并将使用POTS和根盒(RB_DARISH_BM)进行中心卫星实验。我们推测，在干旱条件下，根毛的存在和接种BMS联合体将对玉米的生长表现和根际/根面微生物群更重要。受干旱和/或接种BMS影响的玉米根际微生物群的根毛和空间格局(根尖、根基和不同土壤深度)的作用将以多相和跨学科的方法进行研究(我们小组进行了TC-DNA、qPCR、CLSM、选择性平板和WinRho扩增的MiSeq测序)。对于SPE_BBCH19，我们将参加复杂的抽样以检验以下假设：(I)在大田条件下生长四年后，土壤基质、深度和植株基因型仍然是形成根际微生物群的主要驱动因素，(Ii)利用MisSeq扩增片段测序和qPCR，玉米前茬产生的根残留物和沉淀物将以依赖于土壤基质的方式降解，导致导致再植抑制和微生物生态失调的类群积累。将自组织的概念应用于根际，并采用独特的跨学科方法来研究中心实验，将使我们能够更好地了解根际微生物群落的时空格局及其如何受到外部驱动因素的影响。

The rhizosphere microbiome plays an important role for soil ecosystem functions and plant growth and health. Self-organization of the rhizosphere arises from feedback loops between root, microbiome and soil. In phase I of the SPP2089 we aimed to unravel major external drivers shaping the spatial and temporal rhizosphere microbiome patterns. We investigated the microbiome associated with the rhizosphere of two maize genotypes (wild type (WT) and root hair defective mutant (rth3)) in two distinct soil substrates (loam (L) and sand (S)) in central soil column experiments in a growth chamber (SCE) and a soil plot experiment in the field (SPE). Sequence analysis of 16S rRNA gene and ITS amplicons from total community (TC)-DNAs revealed that the soil substrate was the strongest driver shaping the maize rhizosphere microbiome followed by soil depth and maize genotype (SCE and SPE). Unexpectedly, the presence of maize root hairs had only minor effects on the rhizosphere microbiome, in SCE and SPE. In phase II we will continue to address the hypotheses 1 and 4 and novel questions II, III and IV of the SPP2089 in more detail, to unravel spatial organization of the rhizosphere microbiome of maize depending on the soil texture and the presence of external drivers (inoculation of a consortium of beneficial microorganisms [BMs], drought conditions). We will participate in the central experiments performed both at lab (SCE_Drought) and field (SPE_BBCH19) scale, and will carry out central satellite experiments using pots and rhizoboxes (RB_Drought_BM). We hypothesize that the presence of root hairs and the inoculation of a consortium of BMs will be more important for maize growth performance and rhizosphere/rhizoplane microbiome under drought conditions. The role of root hair and spatial pattern (root tip, root base and different soil depths) of the rhizosphere microbiome of maize affected by drought and/or inoculated BMs will be investigated in a polyphasic and interdisciplinary approach (MiSeq sequencing of amplicons from TC-DNAs, qPCR, CLSM, selective plating and Winrhizo performed by our group). For the SPE_BBCH19, we will participate in the complex sampling to test the following hypotheses: (i) After four years of maize growth under field conditions soil substrate, depth and plant genotype will still be the main drivers shaping the rhizosphere microbiome and (ii) Maize root residues and deposits resulting from previous cropping will be degraded in a soil substrate-dependent manner and result in a build-up of taxa contributing to replant depression and microbial dysbiosis, using the MisSeq amplicon sequencing and qPCR. Applying the concept of self-organization to the rhizosphere and unique interdisciplinary approaches used to investigate the central experiments will enable us to gain a better understanding of the spatiotemporal rhizosphere microbiome patterns and how they are influenced by external drivers.