Phytoremediation capacity of tomato against Sb (III) focusing on the AsA/GSH cycle.

Antimony (Sb) is a toxic metalloid whose presence in the environment has increased in recent years due to anthropogenic activities. In soils, this element may occur as the pentavalent ion Sb(V) (antimonate) or the trivalent ion Sb(III). The latter is more abundant in nature and more harmful to living organisms. In this study, the effects of Sb(III) on a model plant of major agronomic interest - tomato - are investigated in order to elucidate which compounds or metabolic pathways may be key in the plant response to this stressor. In order to achieve this objective, tomato seedlings were cultivated hydroponically and exposed to varying concentrations of Sb(III). This approach ensured optimal availability of the metalloid to the plants. The results of the present study demonstrate that exposure to Sb(III) inhibits plant growth and triggers a range of defence mechanisms, among which proline, phytochelatins (PCs) and enzymes of the AsA/GSH cycle play a prominent role in xenobiotic detoxification. In particular, ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) exhibited significant increases in both content and activity, particularly in roots compared with shoots. In addition to biochemical activity, an assessment was conducted to determine whether the expression of genes encoding these enzymes, as well as those involved in the biosynthetic pathways of the related compounds, was affected. The results of this assessment indicated the same trend. The present study underlines the pivotal function of the AsA/GSH cycle in plant defence in the context of elevated Sb(III) exposure, proposing that roots function as a barrier to restrict the translocation of this metalloid to aerial tissues. These findings may contribute to the identification of species best suited to the remediation of Sb-contaminated environments, based on the enzymes and compounds that play central roles in the defensive response described here. Studies such as the present one contribute to advancing our understanding of the mechanisms by which plants can enhance their remediation capacity and safely restore environments contaminated by xenobiotic compounds.