Pseudomonads associated to salt-stressed plants facilitate stress adaption of soybean through enhanced lignin biosynthesis

Root-associated microbiota play a critical role in plant tolerance to salt stress. However, the conservation of beneficial interactions across diverse crops and soils and the underlying mechanisms remain unclear. Here, we show that pseudomonads were consistently enriched in salt-stressed plant roots across multiple soil types and most crop species. Comparative genomics revealed that these pseudomonads harbored unique genomic signatures associated with high salinity tolerance, such as Na ⁺ transporters. Pseudomonad isolates from salt-stressed plants robustly colonized soybean roots and significantly improved salt tolerance under both greenhouse and field conditions. Pseudomonads-dependent plant salt stress tolerance was mediated through plant lignin biosynthesis stimulation rather than the canonical mechanism of Na ⁺ homeostasis. Overexpression of the key plant lignin biosynthesis genes, including GmCAD , GmCOMT , and Gm4CL , significantly enhanced soybean growth under salt stress. Furthermore, mutant plants deficient in lignin biosynthesis no longer showed pseudomonads-induced salt tolerance. Collectively, our findings reveal a previously unrecognized microbial-mediated pathway that enhances plant resilience to salt stress.