Transcriptomic changes induced in yeast cells by the lack of potassium in the medium

Potassium is the major intracellular cation in S. cerevisiae, which can be concentrated up to 200-300 mM even from relatively low potassium (< 1 mM) environments. This is achieved by mean of a high affinity K+-transport system encoded by the genes TRK1 and TRK2. Recently, our group became interested in the effects of sudden shortage of extracellular potassium. Transcriptomic analysis indicates that lack of potassium drastically alters sulfur metabolism (mainly Met and Cys metabolism), triggers an oxidative stress response and activates the mitochondrial retrograde pathway. We also observe a dramatic halt in the expression of genes required for ribosome biogenesis and translation, as well as decrease in expression of diverse genes (cyclins, protein kinases) required for progression through the cell cycle. Only subsets of these changes were observed in a strain deleted for the TRK1 and TRK2 genes growing in the presence of sufficient potassium (50 mM). Research involving molecular genetics and metabolomic approaches aiming to clarify the primary targets for potassium requirements is currently ongoing. The effect of a sudden shortage of extracellular potassium was studied using a wt yeast strain. Samples of cell cultures grown in either, in the presence or in the absence of potassium, were taken after 10, 20, 40, 60 and 120 min of potassium shortage. We compared the expression profile of: 1) WT w/o K vs WT w/ KCl at 10 min: 2) WT w/o K vs WT w/ KCl at 20 min. 3) WT w/o K vs WT w/ KCl at 40 min. 4) WT w/o K vs WT w/ KCl at 60 min. 5) WT w/o K vs WT w/ KCl at 120 min. Two independent experiments were performed, except for the timepoint of 10 min. For each experiment a dye-swap was carried out. Chips analyzed: 2 for 10 min 4 for 20 min 4 for 40 min 4 for 60 min 4 for 120 min Total number of chips: 18