Selenium increases antimony uptake in As-hyperaccumulators Pteris vittata and Pteris cretica by promoting antimonate reduction: GSH-GSSG cycle and arsenate reductases HAC1/ACR2

Selenium-enhanced arsenic uptake by As-hyperaccumulators Pteris vittata and Pteris cretica is known, but how it impacts antimony (Sb) uptake and associated mechanisms are unclear. Here, we investigated the effects of 2.5 μM selenate (Se_2.5) on Sb uptake by two plants after growing for 10 days under hydroponics containing 10 or 50 μM antimonate (SbV) (Sb₁₀ or Sb₅₀). Both plants were efficient in taking up SbV, which was reduced to SbIII (17–40%) and mainly accumulated in the roots (86−97%). The addition of Se increased the Sb contents by 78–97 and 29–33% to 242–1358 and 132–697 mg kg^-1 in P. vittata and P. cretica roots. Compared with the Sb₁₀ and Sb₅₀ treatments, addition of Se increased the SbV reduction, with more increase in P. vittata than P. cretica roots (181–273% vs. 17–29%). Enhanced GSH-GSSG cycle mediated by glutathione peroxidase (GPX) and glutathione reductase (GR) may play an important role in SbV reduction in the roots. Compared with the Sb treatments, addition of Se increased the GPX and GR activity by 71–97 and 2–50% in P. vittata roots, and 59–153 and 22–63% in P. cretica roots. Besides, Se upregulated the expression of arsenate reductases PvHAC1 and PvACR2 in P. vittata roots by 1.7−3.4 folds but not in P. cretica. Se-enhanced SbV reduction in P. vittata explains why it was more effective in Sb accumulation than P. cretica. Taken together, Se is effective in increasing the Sb uptake in both plants probably by promoting SbV reduction via GSH-GSSG cycle and/or PvHAC1/PvACR2, suggesting that Se may be used to enhance phytostabilization of Sb-contaminated soils.