The root-associated microbiota plays an important role in the response to environmental stress. However, the underlying mechanisms controlling the interaction between salt-stressed plants and microbiota are poorly understood. Here, by focusing on a salt-tolerant plant wild soybean (Glycine soja), we demonstrate that highly conserved microbes dominated by Pseudomonas are enriched in the root and rhizosphere microbiota of salt-stressed plant. Two corresponding Pseudomonas isolates are confirmed to enhance the salt tolerance of wild soybean. Shotgun metagenomic and metatranscriptomic sequencing reveal that motility-associated genes, mainly chemotaxis and flagellar assembly, are significantly enriched and expressed in salt-treated samples. We further find that roots of salt stressed plants secreted purines, especially xanthine, which induce motility of the Pseudomonas isolates. Moreover, exogenous application for xanthine to non-stressed plants results in Pseudomonas enrichment, reproducing the microbiota shift in salt-stressed root. Finally, Pseudomonas mutant analysis shows that the motility related gene cheW is required for chemotaxis toward xanthine and for enhancing plant salt tolerance. Our study proposes that wild soybean recruits beneficial Pseudomonas species by exudating key metabolites (i.e., purine) against salt stress.

根部相关微生物群在应对环境压力中发挥着重要作用。然而，人们对控制盐胁迫植物和微生物群之间相互作用的潜在机制知之甚少。在这里，通过关注耐盐植物野生大豆（Glycine soja ），我们证明以假单胞菌为主的高度保守的微生物在盐胁迫植物的根部和根际微生物群中富集。两个相应的假单胞菌分离株被证实能够增强野生大豆的耐盐性。鸟枪法宏基因组和宏转录组测序表明，运动相关基因（主要是趋化性和鞭毛组装）在盐处理的样品中显着富集和表达。我们进一步发现盐胁迫植物的根部分泌嘌呤，尤其是黄嘌呤，其诱导假单胞菌分离株的运动。此外，向非胁迫植物外源施用黄嘌呤会导致假单胞菌富集，从而重现盐胁迫根中微生物群的变化。最后，假单胞菌突变体分析表明，运动相关基因cheW是黄嘌呤趋化性和增强植物耐盐性所必需的。我们的研究提出，野生大豆通过分泌关键代谢物（即嘌呤）来抵抗盐胁迫，从而招募有益的假单胞菌物种。