Nitrosative stress in fluoride-treated FEX DKO yeast. (A) Liquid growth assay of the combined effect on growth of yeast with fluoride and the IC25 of nitrate (850 mM) or sulfite (20 mM). (B) Serial dilution of FEX DKO cells +/− pRS426 plasmids over a 24-hour period. For H. polymorpha genes SSU2 and NAR1, both plasmids contain the promoter region upstream of the S. cerevisiae SSU1 gene. (C) RT-qPCR of FZF1, YHB1, and SSU1 gene expression over time, compared with one-hour growth in YPD and using actin as a housekeeping gene. (D) Efflux of extracellular nitrate in cells over time. (E) Fold change in intracellular ions of FEX DKO + 50 μM NaF after 24 hours using ICP-MS. SO and PO are oxidized sulfur and phosphorous, respectively.