UIon antagonism strategy for cadmium mitigation in Morchella sextelata: Physiological and metabolomic insights

Cadmium (Cd) contamination in edible fungi poses a significant threat to food safety. However, targeted strategies to regulate Cd uptake and enhance Cd stress tolerance in Morchella sextelata remain largely unexplored. Given that M. sextelata mycelia can autonomously adsorb beneficial metal ions to promote growth, regulating Cd absorption through ion-ion interactions emerges as a promising approach. In this study, under 1 mg/L Cd stress, the exogenous application of Fe²⁺ and Mn²⁺ at a 1:1 M ratio significantly increased mycelial biomass by 20.49 % and 22.11 %, respectively, and effectively reduced Cd accumulation. In contrast, Mg²⁺ led to a moderate biomass increase of 8.94 %. Notably, Fe²⁺ effectively inhibited Cd accumulation in mycelia, reducing Cd content by 81.76 %. Moreover, the addition of divalent ions significantly alleviated osmotic stress in the mycelia, preventing the efflux of sugars and proteins. LC-MS/MS-based metabolomic profiling identified 1446 metabolites. One-way ANOVA revealed distinct metabolic changes associated with metal ion treatments under Cd stress. KEGG pathway enrichment indicated that histidine metabolism plays a key role in the Cd stress mitigation process. VIP (Variable Importance in Projection) analysis further identified key metabolites involved in the repair response. Correlation analysis highlighted carnitine as a core metabolite significantly associated with phenotypic improvements across all treatments. In summary, this study presents the first attempt to regulate Cd accumulation in M. sextelata through divalent ion application. It provides novel insights into the physiological and metabolic mechanisms underlying this ion-mediated mitigation strategy.