Application of glutathione to roots selectively inhibits cadmium transport from roots to shoots in oilseed rape

Abstract

Glutathione is a tripeptide involved in various aspects of plant metabolism. This study investigated the effects of the reduced form of glutathione (GSH) applied to specific organs (source leaves, sink leaves, and roots) on cadmium (Cd) distribution and behaviour in the roots of oilseed rape plants (Brassica napus) cultured hydroponically. The translocation ratio of Cd from roots to shoots was significantly lower in plants that had root treatment of GSH than in control plants. GSH applied to roots reduced the Cd concentration in the symplast sap of root cells and inhibited root-to-shoot Cd translocation via xylem vessels significantly. GSH applied to roots also activated Cd efflux from root cells to the hydroponic solution. Inhibition of root-to-shoot translocation of Cd was visualized, and the activation of Cd efflux from root cells was also shown by using a positron-emitting tracer imaging system (PETIS). This study investigated a similar inhibitory effect on root-to-shoot translocation of Cd by the oxidized form of glutathione, GSSG. Inhibition of Cd accumulation by GSH was abolished by a low-temperature treatment. Root cells of plants exposed to GSH in the root zone had less Cd available for xylem loading by actively excluding Cd from the roots. Consequently, root-to-shoot translocation of Cd was suppressed and Cd accumulation in the shoot decreased.

Cadmium-induced oxidative damage and antioxidant defense mechanisms in Glycine max L.

“…We observed this behavior, where GSH increase responsed to Cd toxicity [11,12] ; also this behavior was observed in previous work in Vigna mungo L. under Cd exposure [13] .…”

“…Stimulation of GSH biosynthesis is frequently observed under adverse conditions; this compound is also a precursor of phytochelatins (PCs), which enable the plant to resist supraoptimal concentrations of heavy metals such as Cd [10][11][12] .…”

“…Although the oxidized glutathione (GSSG) is detected at lower concentrations, the GSH/GSSG ratio influences are more deeply in the control of gene expression and protein function than in the GSH pool [10,12] .…”

“…The tolerance of plants to Cd involves metal detoxification processes, such as complexation with PCs, that are specific chelating compounds [10,11,14,15] . PCs may transport metals from roots to shoots and leaves [12] , and thus the quantification of metals in different plant parts may correlate PCs production with metal accumulation and its transport [16,17] .…”

“…*P<0.05, according to Tukey test. accumulation in several plant species is triggered by ROS availability [10,12,17,22] . In some types of stress, increased synthesis occurs within a context of accumulating GSH, a response that has presumably evolved to offset changes in redox potential caused by increase of GSSG [10] .…”