Our previous studies showed that exogenous glutathione (GSH) decreased cadmium (Cd) concentration in shoots and alleviated the growth inhibition in pakchoi (Brassica chinensis L.) under Cd stress. Nevertheless, it is largely unknown how GSH decreases Cd accumulation in edible parts of pakchoi. This experiment mainly explored the mechanisms of GSH-induced reduction of Cd accumulation in shoot of pakchoi. The results showed that compared with sole Cd treatment, Cd + GSH treatment remarkably increased the expression of BcIRT1 and BcIRT2, and further enhanced the concentrations of Cd and Fe in root. By contrast, GSH application declined the concentration of Cd in the xylem sap. However, these results were not caused by xylem loading process because the expression of BcHMA2 and BcHMA4 had not significant difference between sole Cd treatment and Cd + GSH treatment. In addition, exogenous GSH significantly enhanced the expression of BcPCS1 and promoted the synthesis of PC₂, PC₃ and PC₄ under Cd stress. At the same time, exogenous GSH also significantly improved the expression of BcABCC1 and BcABCC2 in the roots of seedling under Cd stress, suggesting that more PCs-Cd complexes may be sequestrated into vacuoles by ABCC1 and ABCC2 transporters. The results showed that exogenous GSH could up-regulate the expression of BcIRT1/2 to increase the Cd accumulation in root, and the improvement of PCs contents and the expression of BcABCC1/2 enhanced the compartmentalization of Cd in root vacuole of pakchoi under Cd stress. To sum up, exogenous GSH reduce the concentration of free Cd²⁺ in the cytoplast of root cells and then dropped the loading of Cd into the xylem, which eventually given rise to the reduction of Cd accumulation in edible portion of pakchoi.

我们以前的研究表明，外源谷胱甘肽（GSH）降低了芽中镉（Cd）的浓度，并减轻了镉胁迫下小白菜（Brassica chinensis L.）的生长。然而，很大程度上未知的是谷胱甘肽如何减少小菜可食部分中镉的积累。本实验主要探讨了GSH诱导的小白菜芽中Cd积累减少的机理。结果表明，与单独的Cd处理相比，Cd + GSH处理显着增加了BcIRT1和BcIRT2的表达，并进一步提高了根中Cd和Fe的含量。相比之下，GSH的施用降低了木质部汁液中Cd的浓度。但是，这些结果不是由木质部加载过程引起的，因为单独的Cd处理和Cd + GSH处理之间BcHMA2和BcHMA4的表达没有显着差异。此外，外源谷胱甘肽显着增强BcPCS1的表达，并促进Cd胁迫下PC ₂，PC ₃和PC ₄的合成。同时，外源性谷胱甘肽也显着改善了BcABCC1和BcABCC2的表达在镉胁迫下的幼苗根中，表明更多的PCs-Cd复合物可能被ABCC1和ABCC2转运蛋白封存为液泡。结果表明，外源谷胱甘肽可上调BcIRT1 / 2的表达以增加根中Cd的积累，PCs含量的提高和BcABCC1 / 2的表达增强了镉胁迫下小白菜根泡中Cd的分隔性。综上所述，外源性谷胱甘肽降低了根细胞胞质中游离Cd ²⁺的浓度，然后降低了木质部中Cd的负载量，最终导致了小菜可食部分Cd积累的减少。