Table_1_Modulation of the Wheat Seed-Borne Bacterial Community by Herbaspirillum seropedicae RAM10 and Its Potential Effects for Tryptophan Metabolism in the Root Endosphere.DOCX

Plants and their associated microbiota share ecological and evolutionary traits that are considered to be inseparably woven. Their coexistence foresees the use of similar metabolic pathways, leading to the generation of molecules that can cross-regulate each other’s metabolism and ultimately influence plant phenotype. However, the extent to which the microbiota contributes to the overall plant metabolic landscape remains largely unexplored. Due to their early presence in the seed, seed-borne endophytic bacteria can intimately colonize the plant’s endosphere while conferring a series of phytobeneficial services to their host. Understanding the dynamics of these endophytic communities is a crucial step toward the formulation of microbial inoculants that can modulate the functionality of the plant-associated microbiota for improved plant fitness. In this work, wheat (Triticum aestivum) roots non-inoculated and inoculated with the bacterium Herbaspirillum seropedicae strain RAM10 were analyzed to explore the impact of inoculant–endophyte–wheat interrelationships on the regulation of tryptophan (Trp) metabolism in the endosphere environment. Root inoculation with H. seropedicae led to phylum-specific changes in the cultivable seed-borne endophytic community. This modulation shifted the metabolic potential of the community in light of its capacity to modulate the levels of key Trp-related metabolites involved in both indole-3-acetic acid (IAA) biosynthesis and in the kynurenine pathway. Our results support a mode of action of H. seropedicae relying on a shift in both the composition and functionality of the seed-borne endophytic community, which may govern important processes such as root growth. We finally provide a conceptual framework illustrating that interactions among roots, inoculants, and seed-borne endophytes are critical to fine-tuning the levels of IAA in the endosphere. Understanding the outcomes of these interactions is a crucial step toward the formulation of microbial inoculants based on their joint action with seed-borne endophytic communities to promote crop growth and health in a sustainable manner.

植物与其共生的微生物群在生态和进化特性上密不可分，其共存预示着相似代谢途径的利用，进而产生能够相互调节彼此代谢的分子，最终影响植物表型。然而，微生物群对整体植物代谢景观的贡献程度尚未得到充分探索。由于它们在种子中的早期存在，种子携带的内生细菌可以紧密定殖于植物的根围，并向其宿主提供一系列的植物益处服务。理解这些内生菌群的动态变化是制定能够调节与植物相关微生物群功能、以改善植物适应性的微生物接种剂的关键步骤。在本研究中，我们对非接种和接种了Herbaspirillum seropedicae菌株RAM10的麦（Triticum aestivum）根进行了分析，以探索接种剂-内生菌-小麦之间的相互关系对根围环境中色氨酸（Trp）代谢调控的影响。根接种H. seropedicae导致可培养的种子携带内生菌群的门水平变化。这种调节根据其调节关键Trp相关代谢物水平的能力，改变了群落的代谢潜力，这些代谢物不仅参与吲哚-3-乙酸（IAA）的生物合成，还参与犬尿氨酸途径。我们的结果表明，H. seropedicae的作用模式依赖于种子携带内生菌群组成和功能的转变，这可能控制着诸如根生长等重要过程。最后，我们提供了一个概念框架，说明了根、接种剂和种子携带内生菌之间的相互作用对于精确调节根围中IAA水平至关重要。理解这些相互作用的结果是制定基于种子携带内生菌群联合作用、以可持续方式促进作物生长和健康的微生物接种剂的关键步骤。