PT2, PT6, and SPX2 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) andArabidopsismutants 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 PT2/4/6/10, SPX1/2/5/6, and SPX-MFS1. Furthermore, experiments with PT2, PT6, and SPX2 Arabidopsis 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.