Presentation Information
[4Open-03]Role of calcium availability in cadmium uptake and translocation in Cd hyperaccumulator Arabidopsis halleri ssp. gemmifera
○Christine Dwi Ariani Putri Wiyono1, Shuya Awazu1, Motohiro Akashi1, Seiichi Suzuki1 (1. Faculty of Science and Technology, Seikei University, Tokyo (Japan))
Keywords:
Phytoremediation,Arabidopsis halleri ssp. gemmifera,Calcium–cadmium interaction,Cadmium uptake,Cadmium accumulation
Cadmium (Cd) hyperaccumulator plants are promising tools for phytoremediation of heavy-metal-contaminated soils, but the mechanisms controlling Cd uptake and long-distance transport remain unclear. In Arabidopsis halleri ssp. gemmifera, previous RNA-seq analysis showed strong regulation of calcium (Ca)-related genes, including Ca transporters, ion channels, and Ca-dependent signaling components, during Cd exposure. Because Cd2+ and Ca2+ have similar ionic properties, Cd uptake is often assumed to occur through Ca transport pathways. In addition, Ca plays key roles in stress signaling and membrane transport, suggesting that Ca availability may influence Cd accumulation through both transporter competition and signaling processes. However, the role of Ca in Cd accumulation has not been clarified in this hyperaccumulator species.
To examine the effect of Ca availability on Cd accumulation, 3-month-old A. halleri ssp. gemmifera plants were grown hydroponically and exposed for two weeks to five Ca concentrations (0, 0.2, 0.8, 2, and 5 mM) in the presence or absence of 50 µM Cd. This design allowed evaluation of Cd uptake, root retention, and root-to-shoot translocation under different Ca conditions.
Ca availability strongly affected both the amount of Cd taken up and its distribution within the plant. Under Ca-deprived conditions (0 mM), Cd accumulated mainly in roots, reaching about 13.0 mg g-1 DW, while translocation to shoots was very low. At low Ca (0.2 mM), Cd translocation to shoots was highest, and total Cd uptake reached about 40% of the supplied Cd. Increasing Ca concentration reduced Cd accumulation, and at 5 mM Ca the total uptake decreased to about 13%, with root Cd concentrations falling below 1 mg g-1 DW. These results indicate strong competition between Ca and Cd during uptake.
Interestingly, complete Ca deprivation caused strong Cd retention in roots despite high uptake, whereas low Ca promoted efficient root-to-shoot transport. This suggests that Ca is required for long-distance Cd translocation, possibly through Ca-dependent channels or transport systems involved in xylem loading. In contrast, high Ca suppressed Cd uptake, indicating competition at the entry step. Ca accumulation itself was not significantly affected by Cd exposure, suggesting that Cd transport is regulated by Ca-dependent transport activity rather than simple ionic substitution.
Together with previous transcriptomic data, these results suggest that Cd accumulation in A. halleri is controlled by a Ca-related transport network in which Ca availability regulates both uptake and translocation. Ca may act as a switch controlling Cd movement from root to shoot, while high Ca suppresses Cd entry through competition. These findings provide new insight into the mechanism of metal hyperaccumulation and highlight Ca availability as an important factor for optimizing phytoremediation efficiency.
To examine the effect of Ca availability on Cd accumulation, 3-month-old A. halleri ssp. gemmifera plants were grown hydroponically and exposed for two weeks to five Ca concentrations (0, 0.2, 0.8, 2, and 5 mM) in the presence or absence of 50 µM Cd. This design allowed evaluation of Cd uptake, root retention, and root-to-shoot translocation under different Ca conditions.
Ca availability strongly affected both the amount of Cd taken up and its distribution within the plant. Under Ca-deprived conditions (0 mM), Cd accumulated mainly in roots, reaching about 13.0 mg g-1 DW, while translocation to shoots was very low. At low Ca (0.2 mM), Cd translocation to shoots was highest, and total Cd uptake reached about 40% of the supplied Cd. Increasing Ca concentration reduced Cd accumulation, and at 5 mM Ca the total uptake decreased to about 13%, with root Cd concentrations falling below 1 mg g-1 DW. These results indicate strong competition between Ca and Cd during uptake.
Interestingly, complete Ca deprivation caused strong Cd retention in roots despite high uptake, whereas low Ca promoted efficient root-to-shoot transport. This suggests that Ca is required for long-distance Cd translocation, possibly through Ca-dependent channels or transport systems involved in xylem loading. In contrast, high Ca suppressed Cd uptake, indicating competition at the entry step. Ca accumulation itself was not significantly affected by Cd exposure, suggesting that Cd transport is regulated by Ca-dependent transport activity rather than simple ionic substitution.
Together with previous transcriptomic data, these results suggest that Cd accumulation in A. halleri is controlled by a Ca-related transport network in which Ca availability regulates both uptake and translocation. Ca may act as a switch controlling Cd movement from root to shoot, while high Ca suppresses Cd entry through competition. These findings provide new insight into the mechanism of metal hyperaccumulation and highlight Ca availability as an important factor for optimizing phytoremediation efficiency.
Comment
To browse or post comments, you must log in.Log in