Selenium Increased Arsenic Accumulation by Upregulating the Expression of Genes Responsible for Arsenic Reduction, Translocation, and Sequestration in Arsenic Hyperaccumulator .

Selenate enhances arsenic (As) accumulation in As-hyperaccumulator , but the associated molecular mechanisms are unclear. Here, we investigated the mechanisms of selenate-induced arsenic accumulation by exposing to 50 μM arsenate (AsV) and 1.25 (Se) or 5 μM (Se) selenate in hydroponics. After 2 weeks, plant biomass, plant As and Se contents, As speciation in plant and growth media, and important genes related to As detoxification in were determined. These genes included P transporters and (AsV uptake), arsenate reductases and (AsV reduction), and arsenite (AsIII) antiporters and (AsIII translocation) in the roots, and AsIII antiporters and (AsIII sequestration) in the fronds. The results show that Se was more effective than Se in increasing As accumulation in both roots and fronds, which increased by 27 and 153% to 353 and 506 mg kg. The As speciation analyses show that selenate increased the AsIII levels in , with 124-282% more AsIII being translocated into the fronds. The qPCR analyses indicate that Se upregulated the gene expression of by 1.2-fold, and and by 1.0- to 2.5-fold in the roots, and and by 0.6- to 1.1-fold in the fronds under AsV treatment. Though arsenate enhanced gene expression of P transporters and , selenate had little effect. Our results indicate that selenate effectively increased As accumulation in , mostly by increasing reduction of AsV to AsIII in the roots, AsIII translocation from the roots to fronds, and AsIII sequestration into the vacuoles in the fronds. The results suggest that selenate may be used to enhance phytoremediation of As-contaminated soils using .