Poster: Phytoremediation

Abs # 992: Inducible Transport of Cadmium-phytochelatin Complexes

Presenter:	Chang, Katherine N, knc6@cornell.edu
Authors	Chang, Katherine N (A)   Holtmeier, Nikki L (A)   Spanswick, Roger M (A)   Ahner, Beth A (A)
Affiliations:	(A): Cornell University

Molecular manipulation of plants for phytoremediation will require a much better understanding of transport at the cellular level. Previous studies have provided evidence for both Cd²⁺/H⁺ antiport and Cd-phytochelatin (Cd-PC) transport. We have addressed the following: 1) How are vacuolar cadmium transport mechanisms affected by various environmental conditions (i.e. nutrient availability)? 2) Is transport constitutive or inducible? Avena sativa L. was grown hydroponically under nutrient deficiencies. Isolated tonoplast vesicles were assayed for transport (via direct filtration) to determine growth conditions that stimulated Cd-PC transport. Cd-PC vanadate-sensitive transport was present in root tonoplast vesicles harvested from seedlings grown in 0.5 mM CaSO₄ as previously found (Salt & Wagner (1995) Plant Physiol. 107: 1293-1301), and also in macronutrient solutions deficient in nitrate, phosphate, potassium, and magnesium, alone or in combination. Cd-PC transport was not measurable in vesicles isolated from plants grown in a full nutrient solution. Exposure to cadmium (0.5, 1, 5 mM CdCl₂ for 48 hours) may stimulate vacuole sequestration of cadmium. Increasing Cd had a detrimental effect on the viability (e.g. ATPase activity) of the vesicles, which we hypothesize is responsible for decreased Cd-PC transport at high Cd concentrations. Cd-PC transport appears to be stimulated by both nutrient deficiencies and Cd stress.