Deciphering the Dynamic Interplay between Rhizobacteria and Root Exudates via Cerium Oxide Nanomaterials Modulation for Promoting Soybean Yield and Quality

The interplay between root exudates and rhizobacteria is essential for enhancing agricultural productivity. Herein, the impacts of cerium dioxide nanomaterials (CeO2 NMs) on these interactions in soybean plants were investigated. Following 3–5 weeks of exposure to 5 mg·kg–1 CeO2 NMs, the composition of root exudates changed over time, with isoflavone levels increasing by 6.3–21.7 folds, potentially manipulating the rhizobacteria. Correspondingly, rhizobacteria such as Ensifer, Allorhizobium, Nitrospira, and Bradyrhizobium were enriched by 40.7–367.3% at three time points. CeO2 NMs stimulated isoflavone biosynthesis in soybean plants and their excretion into the rhizosphere via upregulating the expressions of MYB transcription factors, biosynthesis, and transporter genes. The interactions of root exudates and rhizobacteria mediated by CeO2 NMs enhanced plant biomass (45.5–75.9%), nodulation (85.7%), nitrogen fixation, nutrient acquisition, and soil health, improving soybean quality (34.4–223.9%) and yield (16.2%). This study provides insights into root exudate-rhizobacteria interactions in leguminous plants facilitated by NMs for sustainable agriculture.