Arbuscular mycorrhizal fungi confer aluminum toxicity tolerance in Ricinus communis via modulating root metabolic mechanisms and the composition and quantity of root exudates.

Aluminum (Al) phytotoxicity is an essential factor that severely threatens plant productivity in acidic soil with pH < 5. Nevertheless, the specific interactions and functional contributions of arbuscular mycorrhizal fungus (AMF) in the adaptability of Ricinus communis to Al stress remain poorly understood. In this study, we investigated the changes in biomass, Al accumulation, antioxidant system, sucrose metabolism, gene expression, and root exudates of R. communis when regulated by AMF (Rhizophagus intraradices, Funneliformis mosseae, and Diversispora versiformis) under Al stress (0-1.2 g kg). Al detoxification by AMF - R. communis symbiosis was manifested by activating antioxidant levels, sucrose metabolism, thereby alleviating lipid peroxidation (MDA decreased 11.44 %-24.89 %) and increasing plant biomass (10.34 %-33.33 %). Meanwhile, transcriptome analysis revealed 659 differentially expressing genes (DEGs) in AMF-inoculated plants in comparison to non-inoculated plants subjected to Al stress. Furthermore, AMF colonization induced 929 differential metabolites (DAMs) from the perspective of root exudates. The integrating analysis of gene expression and root exudate changes indicating that AMF colonization under Al stress was closely related to ABC transporters, glutathione metabolism, nitrogen metabolism, cyanoamino acid metabolism, starch and sucrose metabolism. Altogether, the result of this study suggest that AMF confer Al tolerance to R. communis via antioxidant activation, sucrose metabolism regulation, and reshaping root exudates and gene networks. The present study provides new insights into the crucial role of AMF in improving Al-tolerance of R. communis.