Evolutionary engineering of an iron-resistant Saccharomyces cerevisiae mutant and its physiological and molecular characterization

Iron plays an essential role in all organisms and is involved in the structure of many biomolecules. It also regulates the Fenton reaction where highly reactive hydroxyl radicals occur. Excessive iron levels can cause oxidative damage in cells. Saccharomyces cerevisiae evolved mechanisms to regulate its iron levels. To study the iron stress response of S. cerevisiae, evolutionary engineering was employed. The evolved iron stress-resistant mutant “M8FE” was analyzed physiologically, transcriptomically and by whole genome re-sequencing. M8FE showed cross-resistance to other transition metals: cobalt, chromium, and nickel. M8FE seemed to cope with the iron stress by both avoidance and sequestration strategies. PHO84, encoding the high-affinity phosphate transporter, was the most down-regulated gene in the mutant, and may play a crucial role in iron-resistance. M8FE had upregulated many oxidative stress response, reserve carbohydrate metabolism, and mitophagy genes; while ribosome biogenesis genes were downregulated. As a possible result of the induced oxidative stress response genes, lower intracellular oxidation levels were observed. M8FE also had high trehalose and glycerol production levels, with the GPH1, PGM2, and TSL1 genes upregulated. Genome re-sequencing analyses indicated mutations that emphasize the potential roles of phosphate transport and metabolism, cell wall, and multidrug resistance-related transcription factors.