Knockouts of Yeast Plasma Membrane Phosphate Transporters Alter Resistance to Heavy Metals

Mutant yeast strains with altered sensitivity to heavy metals are crucial for revealing the mechanisms of metal absorption and detoxification, as well as for bioremediation of these pollutants. Here, we show that a knockout of the PHO87 gene encoding the low-affinity phosphate transporter of the cytoplasmic membrane of S. cerevisiae increased resistance to manganese, silver, and vanadate ions. However, a knockout of PHO90 (PHO87 paralog) did not affect the sensitivity to silver and vanadate ions but increased sensitivity to manganese ions. The Δpho87 cells accumulated 10 times less manganese compared to the wild-type cells, while the Δpho90 cells accumulated two times more manganese compared to the wild-type cells, when grown in YPD with 2 mM MnSO4. The polyphosphate content of the Δpho84, Δpho87, and Δpho90 cells cultivated at high phosphate concentration did not differ from that of the wild-type strain. In the presence of 2 mM MnSO4, Δpho87 cells contained several times less polyphosphates, and Δpho90 cells contained more short-chain polyphosphates than the cells of the wild-type strain. We hypothesize that phosphate carriers participate in the regulation of heavy metal uptake, and the respective knockouts are useful in bioremediation and bioassay of these pollutants.