On the role of Trk1 and Trk2 in Schizosaccharomyces pombe under different ion stress conditions

Trk1 and Trk2 are the major K+ transport systems in Schizosaccharomyces pombe. Both transporters individually seem to be able to cope with K+ requirements of the cells under normal conditions, since only the double mutant shows defective K+ transport and defective growth at limiting K+ concentrations. We have studied in detail the role of SpTrk1 and SpTrk2 under different ion stress conditions. Results show that the strain with only Trk1 (trk1(+)) is less sensitive to Li+ and to hygromycin B, it grows better at low K+ and it survives longer in a medium without K+ than the strain expressing only Trk2 (trk2(+)). We conclude that Trk1 contributes more efficiently than Trk2 to the performance of the fission yeast under ion stress conditions. In the wild type both trk1(+) and trk2+ genes are expressed and probably collaborate for the performance of the cells. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.