Contribution of glutathione to the control of cellular redox homeostasis under toxic metal and metalloid stress

Abstract

The accumulation of toxic metals and metalloids, such as cadmium (Cd), mercury (Hg), or arsenic (As), as a conse quence of various anthropogenic activities, poses a serious threat to the environment and human health. The ability

of plants to take up mineral nutrients from the soil can be exploited to develop phytoremediation technologies able

to alleviate the negative impact of toxic elements in terrestrial ecosystems. However, we must select plant species

or populations capable of tolerating exposure to hazardous elements. The tolerance of plant cells to toxic elements

is highly dependent on glutathione (GSH) metabolism. GSH is a biothiol tripeptide that plays a fundamental dual role:

first, as an antioxidant to mitigate the redox imbalance caused by toxic metal(loid) accumulation, and second as a

precursor of phytochelatins (PCs), ligand peptides that limit the free ion cellular concentration of those pollutants. The

sulphur assimilation pathway, synthesis of GSH, and production of PCs are tightly regulated in order to alleviate the

phytotoxicity of different hazardous elements, which might induce specific stress signatures. This review provides an

update on mechanisms of tolerance that depend on biothiols in plant cells exposed to toxic elements, with a particular

emphasis on the Hg-triggered responses, and considering the contribution of hormones to their regulation