High-Affinity Sulfate Transporter Sultr1;2 Is a Major Transporter for Cr(VI) Uptake in Plants.

Chromate (Cr[VI]) is a highly phytotoxic contaminant that is ubiquitous in soils. However, how Cr(VI) is taken up by plant roots remains largely unknown. Here, we show that the high-affinity sulfate transporter Sultr1;2 is responsible for Cr(VI) uptake by the roots of Arabidopsis thaliana. Sultr1;2 showed a much higher transport activity for Cr(VI) than Sultr1;1 when expressed in yeast cells. Knockdown of Sultr1;2 expression in Arabidopsis markedly reduced the Cr(VI) uptake rate, whereas knockout of Sultr1;1 had no or little effect. A double-knockout mutant (DKO) of the two genes lost the ability of Cr(VI) uptake almost completely. The Sultr1;2 knockdown mutant or DKO plants displayed higher resistance to Cr(VI) under normal sulfate conditions as a consequence of the lower tissue Cr accumulation. Overexpression of Sultr1;2 substantially increased Cr(VI) uptake with shoot Cr concentration being 1.6-2.0 times higher than that in the wild-type. These results indicate that Sultr1;2 is a major transporter responsible for Cr(VI) uptake in Arabidopsis, while Sultr1;1 plays a negligible role. Taken together, our study has identified a major transporter for Cr(VI) uptake in plants, providing potential strategies for engineering plants with low Cr accumulation and consequently enhanced Cr(VI) resistance and also plants with enhanced accumulation of Cr for the purpose of phytoremediation.