LAUSR

In nature, plants need to acquire nutrients from soils to sustain growth, and at the same time they need to avoid uptake and/or be endowed with tolerance systems to cope with toxic compounds. This is particularly challenging when the toxic compound and the nutrient are chemically similar, as it is the case of phosphate and arsenate. Here we demonstrate that regulatory elements of the phosphate starvation response (PSR) coordinate the arsenate detoxification machinery in the cell. We show that arsenate repression of the phosphate transporter PHT1;1 is linked 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. We also identified an arsenite responsive SKP1-like protein and a PHR1 interactor F-box (PHIF1) as constituents of the SCF complex responsible for PHR1 degradation. Furthermore, we found that arsenite, the form to which arsenate is reduced towards compartmentalization in vacuoles, represses PHT1;1 expression, providing a highly selective signal versus phosphate to control PHT1;1 expression in response to arsenate. Our results provide the molecular insights into a sensing mechanism that regulates arsenate/phosphate uptake depending on the plants' detoxification capacity.