Transcriptome and ultrastructural analysis revealed the mechanism of Mercapto-palygorskite on reducing Cd content in wheat

Large areas of crop yields in northern China have faced with cadmium (Cd) contamination problems. Mercaptomodified palygorskite (MP), as a highly efficient immobilization material, could reduce Cd absorption in wheat and alleviate its biotoxicity. However, the molecular mechanism underlying MP-mediated Cd reduction and detoxification processes in wheat is not well understood. This aim of this study was to investigate the biochemical and molecular mechanisms underlying the reduction in Cd accumulation in wheat (Triticum aestivum L.). The results showed that MP application decreased the Cd concentration by 68.91-74.32% (root) and 70.68-77.2% (shoot), and significantly increased the glutathione (GSH) and phytochelatins (PCs) contents in root and shoot. In addition, with the application of MP, the percentage of Cd in the cell walls and organelles of wheat decreased, while that of Cd in soluble components was increased. The content of Cd in all components was significantly reduced. Ultrastructural analysis revealed that MP thickened the cell wall, promoted vesicle formation in the membrane and protected the integrity of intracellular organelles in wheat. Transcriptome analysis further confirmed the above results. MP upregulated the expression of several genes (CCR, CAD COMT and SUS) involved in cell wall component biosynthesis and promoted vesicle formation on cell membranes by upregulating the expression of PLC and IPMK genes. In addition, genes related to antioxidant synthesis (PGD, glnA and GSS) and photosynthesis (Lhca, Lhcb) were altered by MP to alleviate Cd toxicity in wheat. This present work will help to more thoroughly elucidate the molecular mechanism by which wheat defends against Cd contamination under MP application and provide and important research basis for the application of this material in the future.