National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China; Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai 200234, China.
National Key Laboratory of Plant Molecular Genetics, Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China; College of Forestry, Northwest A&F University, Yangling 712100, China.
Mol Plant. 2021 Mar 1;14(3):503-516. doi: 10.1016/j.molp.2020.12.002. Epub 2020 Dec 9.
Plants establish symbioses with mutualistic fungi, such as arbuscular mycorrhizal (AM) fungi, and bacteria, such as rhizobia, to exchange key nutrients and thrive. Plants and symbionts have coevolved and represent vital components of terrestrial ecosystems. Plants employ an ancestral AM signaling pathway to establish intracellular symbioses, including the legume-rhizobia symbiosis, in their roots. Nevertheless, the relationship between the AM and rhizobial symbioses in native soil is poorly understood. Here, we examined how these distinct symbioses affect root-associated bacterial communities in Medicago truncatula by performing quantitative microbiota profiling (QMP) of 16S rRNA genes. We found that M. truncatula mutants that cannot establish AM or rhizobia symbiosis have an altered microbial load (quantitative abundance) in the rhizosphere and roots, and in particular that AM symbiosis is required to assemble a normal quantitative root-associated microbiota in native soil. Moreover, quantitative microbial co-abundance network analyses revealed that AM symbiosis affects Rhizobiales hubs among plant microbiota and benefits the plant holobiont. Through QMP of rhizobial rpoB and AM fungal SSU rRNA genes, we revealed a new layer of interaction whereby AM symbiosis promotes rhizobia accumulation in the rhizosphere of M. truncatula. We further showed that AM symbiosis-conditioned microbial communities within the M. truncatula rhizosphere could promote nodulation in different legume plants in native soil. Given that the AM and rhizobial symbioses are critical for crop growth, our findings might inform strategies to improve agricultural management. Moreover, our work sheds light on the co-evolution of these intracellular symbioses during plant adaptation to native soil conditions.
植物与互惠共生真菌（如丛枝菌根真菌）和细菌（如根瘤菌）建立共生关系，以交换关键养分并茁壮成长。植物和共生体共同进化，是陆地生态系统的重要组成部分。植物利用祖先的丛枝菌根信号通路在其根部建立细胞内共生关系，包括豆科植物-根瘤菌共生关系。然而，在原生土壤中，丛枝菌根和根瘤菌共生关系之间的关系尚未得到很好的理解。在这里，我们通过对 16S rRNA 基因进行定量微生物组学（QMP）分析，研究了这些不同的共生关系如何影响紫花苜蓿根相关细菌群落。我们发现，不能建立丛枝菌根或根瘤菌共生关系的紫花苜蓿突变体在根际和根部的微生物负荷（定量丰度）发生改变，特别是丛枝菌根共生关系是在原生土壤中组装正常定量根相关微生物群所必需的。此外，定量微生物共丰度网络分析表明，丛枝菌根共生关系影响植物微生物群中的根瘤菌目枢纽，并有益于植物整体共生体。通过对根瘤菌 rpoB 和丛枝菌根 SSU rRNA 基因的 QMP 分析，我们揭示了一个新的互作层面，即丛枝菌根共生关系促进根瘤菌在紫花苜蓿根际的积累。我们进一步表明，丛枝菌根共生条件下的微生物群落可以在原生土壤中促进不同豆科植物的结瘤。鉴于丛枝菌根和根瘤菌共生关系对作物生长至关重要，我们的研究结果可能为改善农业管理提供策略。此外，我们的工作揭示了这些细胞内共生关系在植物适应原生土壤条件过程中的共同进化。
