<i>PT2</i> , <i>PT6</i> , and <i>SPX2</i> Responsible for Phosphate Uptake/Translocation May Also Be Involved in Antimonate Uptake

Antimony (Sb) is a toxic and carcinogenic metalloid. Antimonite [Sb(III)] enters plant cells through aquaporins (AQPs), while antimonate [Sb(V)] may enter via transporters involved in the uptake of nitrate (NO₃^-), phosphate (PO₄^3-), or chloride (Cl^-). However, direct evidence of this hypothesis is still lacking. In this study, we conducted hydroponic experiments with rice (YongYou 9) and<i>Arabidopsis</i>mutants to explore the effects of phosphorus (P) and Sb interactions on Sb uptake in plant roots. We discovered several key findings: (1) Sb(III) consistently exhibited toxicity to plants, irrespective of P concentrations, whereas Sb(V) toxicity to plants was influenced by P levels; (2) both Sb(III) and Sb(V) promoted the formation of iron plaques on rice roots, especially with Sb(III) exposure; (3) P inhibited Sb(V) uptake in rice roots but conditionally enhanced Sb uptake when exposed to Sb(III); (4) at 10 mg L^-1 Sb(V) exposure, P downregulated the expression of genes like <i>PT2/4/6/10</i>, <i>SPX1/2/5/6</i>, and <i>SPX</i>-<i>MFS1</i>. Furthermore, experiments with <i>PT2</i>, <i>PT6</i>, and <i>SPX2</i> <i>Arabidopsis</i> mutants confirmed these genes' involvement in Sb(V) uptake. This study demonstrates that plants may utilize P uptake channels to absorb Sb(V) and highlights the potential risks of using P fertilizers in Sb-contaminated rice fields.