Arsenite provides a selective signal that coordinates arsenate uptake and detoxification through the regulation of PHR1 stability in Arabidopsis.

In nature, plants acquire nutrients from soils to sustain growth, and at the same time, they need to avoid the uptake of toxic compounds and/or possess tolerance systems to cope with them. This is particularly challenging when the toxic compound and the nutrient are chemically similar, as in the case of phosphate and arsenate. In this study, we demonstrated that regulatory elements of the phosphate starvation response (PSR) coordinate the arsenate detoxification machinery in the cell. We showed that arsenate repression of the phosphate transporter PHT1;1 is associated with the degradation of the PSR master regulator PHR1. Once arsenic is sequestered into the vacuole, PHR1 stability is restored and PHT1;1 expression is recovered. Furthermore, we identified an arsenite responsive SKP1-like protein and a PHR1 interactor F-box (PHIF1) as constituents of the SCF complex responsible for PHR1 degradation.We found that arsenite, the form to which arsenate is reduced for compartmentalization in vacuoles, represses PHT1;1 expression, providing a highly selective signal versus phosphate to control PHT1;1 expression in response to arsenate. Collectively, our results provide molecular insights into a sensing mechanism that regulates arsenate/phosphate uptake depending on the plant's detoxification capacity.