ARS | Publication request: CORRELATING THIOL AND CADMIUM CONCENTRATIONS IN TISSUES OF NEAR ISOGENIC LINES OF DURUM WHEAT THAT DIFFER IN GRAIN CADMIUM ACCUMULATION

Submitted to: Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: June 18, 2000
Publication Date: N/A

Technical Abstract: Cadmium concentrations in durum wheat grain grown in cadmium-containing soils of the North American Great Plains often exceed limits proposed by international trade organizations. It is therefore important to understand the physiological mechanisms that lead to high grain Cd levels. In this work, near-isogenic lines of durum wheat that differ about three-fold in grain Cd accumulation were used to study Cd partitioning within plants. Results show that the low grain Cd-accumulating isoline exhibits a lower shoot/root Cd concentration ratio than the high Cd-accumulating isoline. Because phytochelatins (PCs) are known to function in sequestering Cd in root vacuoles, we hypothesized that they are involved with differential Cd partitioning. We used a newly developed, highly sensitive capillary electrophoresis method to detect thiols, including phytochelatins, in tissues from the two isolines. The technique uses laser-induced fluorescence detection of the thiol-reacting compound 5-(bromomethyl) fluorescein. Detection of amounts of glutathione as low as 10-15 mole has been achieved with this method, making it possible to measure thiol concentrations in small tissue samples. Initial results from the two durum wheat isolines show that there are higher concentrations of glutathione and cysteinyl-glycine in extracts from root tips than in more basal root sections. Root tip extracts from the Cd-accumulating isoline had higher levels of thiols than in the Cd non-accumulating isoline. These results are analyzed with respect to the hypothesis that phytochelatin-related metabolism and/or compartmentation is responsible for the differential partitioning and grain accumulation of Cd in the two durum wheat isolines.