基于LC-MS非靶向代谢组学解析土壤铅胁迫下狗牙根根系代谢物变化及耐性机制OA

Plant root exudates are the key chemical signals and regulatory factors for plant response to environmental stress,and their composition changes directly affect the bioavailability of heavy metals in the rhizosphere and plant adaptability.In this study,using liquid chromatography-mass spectrometry(LC-MS)untargeted metabolomics,the metabolite changes in root exudates of Cynodon dactylon were systematically analyzed under soil Pb stress at concentrations of 500 and 1 000 mg/kg,and the tolerance mechanism of C.dactylon to soil Pb was revealed.The results showed that C.dactylon in the 500 mg/kg Pb treatment group exhibited higher root length,plant height,and leaf biomass compared with the 1 000 mg/kg Pb treatment group.Additionally,soil Pb stress reduced the contents of nitrogen,phosphorus and chlorophyll in leaves and roots of C.dactylon,indicating that soil Pb stress inhibited the absorption of nitrogen and phosphorus in soil and photosynthesis of C.dactylon.Different concentrations of soil Pb stress changed the metabolite components of C.dactylon root exudates,and a total of 1 028 differential metabolites were identified(VIP＞1,P＜0.05).The relative contents of DL-malic acid and γ-aminobutyric acid(GABA)in root exudates increased at 500 mg/kg soil Pb treatment group,but decreased at 1 000 mg/kg soil Pb treatment group.The metabolic response of C.dactylon to soil Pb stress revealed 2 key metabolic pathways associated with GABA:The GABAergic synapse pathway and butanoate metabolism pathway.These significantly enriched pathways under metal stress contributed to alleviating Pb-induced oxidative damage and ameliorating the imbalance in energy metabolism,and DL-malic acid had the ability to chelate heavy metals to reduce the bioavailability of Pb.Therefore,the organic acids(DL-malic acid,fumaric acid)and GABA in the root exudates of C.dactylon jointly mediated the formation of a synergistic detoxification network of'chelation-transport-antioxidation'to alleviate the stress of soil heavy metal Pb on plants.This study provides a theoretical basis for the regulation of plant rhizosphere metabolism on soil heavy metal Pb remediation technology.