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Arsenic-hyperaccumulator Pteris vittata exhibits remarkable absorption ability for chromium (Cr) while beneficial element selenium (Se) helps to reduce Cr-induced stress in plants. However, the effects of Se on the Cr uptake and the associated mechanisms in P. vittata are unclear, which were investigated in this study. P. vittata plants were grown for 14 days in 0.2-strength Hoagland solution containing 10 (Cr 10) or 100 μM (Cr 100) chromate (CrVI) and 1 μM selenate (Se 1). The plant biomass, malondialdehyde contents, total Cr and Se contents, Cr speciation, expression of genes associated with Cr uptake, and Cr subcellular distribution in P. vittata were determined. P. vittata effectively accumulated Cr by concentrating 96–99% in the roots under Cr 100 treatment. Further, Se substantially increased its Cr contents by 98% to 11,596 mg kg−1 in the roots, which may result from Se's role in reducing its oxidative stress as supported by 27–62% reduction in the malondialdehyde contents. Though supplied with CrVI, up to 98% of the Cr in the roots was reduced to insoluble chromite (CrIII), with 83–89% being distributed on root cell walls. Neither Cr nor Se upregulated the expression of sulfate transporters PvSultr1;1 − 1;2 or phosphate transporter PvPht1;4 , indicating their limited role in Cr uptake. P. vittata effectively accumulates Cr in the roots mainly as CrIII on cell walls and Se effectively enhances its Cr uptake by reducing its oxidative stress. Our study suggests that Se can be used to enhance P. vittata Cr uptake and reduce its oxidative stress, which may have application in phytostabilization of Cr-contaminated soils. [Display omitted] • P. vittata effectively accumulates Cr by concentrating 96–99 % in the roots at 100 μM CrVI. • Selenate promotes Cr uptake by 98% to 11,596 mg kg-1 in the roots at 100 μM CrVI. • Selenate reduces its oxidative stress as evidenced by 27–62% decrease in its MDA. • 94–99% CrVI is reduced to CrIII in the roots, with 83–89% on cell walls. [ABSTRACT FROM AUTHOR]

In contaminated soils, arsenic (As) often co-exists with copper (Cu). However, its effects on As accumulation and the related mechanisms in As-hyperaccumulator Pteris vittata remain unclear. In this study, P. vittata plants were exposed to 50 µM As and/or 50 µM Cu under hydroponics to investigate the effects of Cu on plant growth and As accumulation, as well as gene expression related to arsenic uptake (P transporters), reduction (arsenate reductases), and translocation and sequestration (arsenite antiporters). After 14 d of growth and compared to the As treatment, the As concentration in P. vittata fronds increased by 1.4-times from 793 to 1131 mg·kg−1 and its biomass increased by 1.2-fold from 18.0 to 21.1 g·plant−1 in the As+Cu treatment. Copper-enhanced As accumulation was probably due to upregulated gene expressions related to As-metabolisms including As uptake (1.9-fold in P transporter PvPht1;3), translocation (2.1–2.4 fold in arsenite antiporters PvACR3/3;2) and sequestration (1.5–2.0 fold in arsenite antiporters PvACR3;1/3;3). Our results suggest that moderate amount of Cu can help to increase the As accumulation efficiency in P. vittata , which has implication in its application in phytoremedation in As and Cu co-contaminated soils. [Display omitted] • 50 µM Cu enhanced plant growth and As accumulation in P. vittata. • P. vittata maintains a normal Cu level in fronds by concentrating most Cu in roots. • Cu promoted AsV uptake by upregulating P transporter PvPht1;3. • Cu upregulated AsIII antiporters PvACR3-3;3 for As translocation and sequestration. [ABSTRACT FROM AUTHOR]