The Nha1 Na+(K+)/H+ antiporter is a constitutively expressed housekeeping protein that uses the inward gradient of H+ (created by the Pma1 H+-ATPase) as a driving force to export alkali metal cations and whose activity plays a role in the maintenance of

plasma-membrane potential and regulation of cell volume and internal pH (Sychrova et al., 1999; Kinclova-Zimmermannova et al., 2006; Arino et al., 2010). The third system exporting alkali metal cations, Ena Na+(K+)-ATPase (Haro et al., 1991), is the main sodium and lithium detoxifying system in S. cerevisiae, but it also contributes significantly to high potassium tolerance (Banuelos et al., 1998). To study the role of the five main S. cerevisiae potassium transporters in anhydrobiosis, we used a set of isogenic strains lacking buy Tanespimycin one or more genes encoding the plasma-membrane K+ transporters in the BY4741 genetic background and studied

the ability of mutant cells to survive desiccation and the subsequent rehydration processes. Our results revealed buy ZD1839 that whereas the functionality of potassium exporting systems is not important for surviving desiccation, it is the activity of potassium uptake systems, and mainly that of Trk2, which is crucial to successfully survive anhydrobiosis. The S. cerevisiae BY4741 strain (MATa his3Δ1 leu2Δ met15Δ ura3Δ; EUROSCARF) and its derivatives were used. Mutants

lacking genes for potassium transporters were prepared by homologous recombination using the Cre-loxP system (Guldener et al., 1996) and their genotypes are listed in Table 1. To verify learn more the phenotypes of single trk1Δ or trk2Δ mutants, two or three independently prepared mutants were used. Yeast strains were routinely grown in standard liquid YPD medium (1% extract, 2% peptone, 2% glucose) supplemented with 50 mM or 100 mM KCl in an orbital shaker at 160 r.p.m. min−1 at 30 °C. Solid YPD media were supplemented with 2% agar. To follow the growth resumption of stationary cells, the growth rate of 100-μL cultures in a 96-well plate was followed in an absorbance microplate reader (BioTek Instruments, Winooski, VT); eight parallel cultures for one strain were run in each experiment, and the experiment was repeated three times. Yeast cells were grown to the stationary phase (40–42 h) in YPD with 50 mM KCl, harvested, washed and dehydrated by convective drying at 30 °C for 15–16 h. Dehydrated biomass was rehydrated in distilled water or in 50 mM KCl for 10 min at room temperature. Cell survival was estimated using either the fluorochrome primulin and fluorescence microscopy (Rapoport & Meysel, 1985) or after appropriate dilution of the rehydrated biomass, plating on solid YPD with 50 mM KCl and counting the colonies (CFU) after 2 days of growth at 30 °C.