Characterization of Cd uptake in roots and translocation from roots to shoots in Solanum melongena and Solanum torvum

Cadmium (Cd) concentration in eggplant (Solanum melongena) fruits can be drastically reduced by grafting them with Solanum torvum rootstock. However, mechanisms of Cd uptake in roots and translocation from roots to shoots in both plants are not understood well. We thus characterized symplastic Cd uptake in roots and translocation from roots to shoots via xylem loading process of both plants. Additionally, we also examined effect of other elements in roots uptake and translocation process with the increase of Cd concentration in the medium. Cd concentration in roots of S. torvum was almost similar to that of S. melongena for 7 days. On the other hand, Cd concentrations in the shoots and xylem sap were higher in S. melongena than in S. torvum. A concentration dependent experiment in roots indicated that Km values were almost the same for species, but the Vmax values were 1.5-fold higher in S. melongena than in S. torvum. A concentration dependent experiment in xylem loading process indicated that Km values were approximately 7-fold higher in S. torvum than in S. melongena. These results suggest that xylem loading process is a critical factor for determining Cd accumulation in the shoots of both plants. Several elements concentration in roots and xylem sap of both plants decreased with the increase of Cd concentration in the medium, suggesting that Cd uptake and translocation process are partly mediated by similar transporters involving these elements transport.