Silica Nanoparticles and Synthetic Communities Enhance Soybean Salt Tolerance through 5-Aminovaleric Acid-Mediated...

We first constructed functionally complementary synthetic communities (SynC) based on functional traits and phylogenetic similarity to core taxa enriched under silica nanoparticles (SiO2 NPs) treatment. Then, we evaluated their combined effects with SiO2 NPs in alleviating soybean salt stress. In a 37-day pot experiment under 200 mM NaCl, combined application reduced the shoot Na+/K+ ratio by 24.7%-33.2% compared to either treatment alone. Furthermore, the rhizosphere microbiome was markedly restructured, with an enrichment of Sphingomonas, which was identified as a major contributor to salt tolerance through ion homeostasis and niacin and nicotinamide metabolism. Notably, 5-aminovaleric acid (5-AVA) was significantly positively correlated to the abundance of Sphingomonas. Exogenous application of 5-AVA enriched Sphingomonas populations by 33.9% and enhanced soybean growth under salt stress. Our findings demonstrate that the combined application enhances soybean salt tolerance by altering the root exudate composition and enriching beneficial bacteria, providing a promising strategy for advancing sustainable agriculture under salt stress.