Cadmium Adsorption in Leaf Cell Walls Prevents Redistribution to Silique in Arabidopsis Thaliana Ecotypes Jm-1 and Kyo-0

Abstract Background: Along with the rapid progress of industrialization and urbanization in the world, soil Cd pollution has become an increasingly serious problem. Phytoremediation has been widely used to mitigate heavy metal pollution in soils; however, it is difficult to reduce the Cd content in the grains of food crops using Cd pollution remediation techniques. Results: Here, we found that the Cd concentrations in the leaves, stems, and siliques of Arabidopsis thaliana (A. thaliana) ecotype Jm-1 were higher than in the ecotype Kyo-0. The Cd concentrations in the cell walls (CW) of the leaves were lower in Jm-1 than in Kyo-0, while the concentrations in the CW of the stem and silique were significantly higher in Jm-1 than in Kyo-0. The Cyclohexane Diamine Tetraacetic Acid (CDTA)-pectin and hemicellulose in Kyo-0 had higher Cd concentrations than those of Jm-1. The pectin methylesterase (PME) activity was higher in Kyo-0 than in Jm-1, and the expression levels of PME1, PME2, PME12, and PME25 were upregulated in Kyo-0 after Cd treatment. In addition, no significant differences in the Cd concentrations were found in the xylem of the two ecotypes, while the Cd concentration in the phloem was significantly higher in Jm-1 than in Kyo-0. The expression of iron transport-related genes showed that only YSL3 and ZIP11 had significant differences between the two ecotypes after Cd treatment, and the expression of the vacuolar Cd compartment-related genes that are responsible for transferring Cd from the cytoplasm to the vacuole showed that only CAX1 expression was significantly higher in Kyo-0 than in Jm-1. Conclusions: Kyo-0 accumulated less Cd than Jm-1 in the silique, which may be because (1) the activity of PME that is mainly regulated by PME1, PME2, PME12, and PME25 was higher in Kyo-0 leaves, leading to more Cd chelation in the pectin of the CWs, and (2) the expression of YSL3 was induced to regulate the transport of Cd in the phloem, thus reducing the transport of Cd to the silique. This study would benefit future research and agricultural practices.