title: Gene amplification at a locus encoding a putative Na+/H+ antiporter confers sodium and lithium tolerance in fission yeast.
abstract: We have identified a new locus, sodium 2 (sod2) based on selection for increased LiCl tolerance in fission yeast, Schizosaccharomyces pombe. Tolerant strains have enhanced pH-dependent Na+ export capacity and sodium transport experiments suggest that the gene encodes an Na+/H+ antiport. The predicted sod2 gene product can be placed in the broad class of transporters which possess 12 hydrophobic transmembrane domains. The protein shows some sequence similarity to the human and bacterial Na+/H+ antiporters. Overexpression of sod2 increased Na+ export capacity and conferred sodium tolerance. Osmotolerance was not affected and sod2 cells were unaffected for growth in K+. In a sod2 disruption strain cells were incapable of exporting sodium. They were hypersensitive to Na+ or Li+ and could not grow under conditions that approximate pH7. The sod2 gene amplification could be selected stepwise and the degree of such amplification correlated with the level of Na+ or Li+ tolerance.
authors.affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada.
authors.forename: Z P
authors.initials: ZP
authors.lastname: Jia
authors.forename: N
authors.initials: N
authors.lastname: McCullough
authors.forename: R
authors.initials: R
authors.lastname: Martel
authors.forename: S
authors.initials: S
authors.lastname: Hemmingsen
authors.forename: P G
authors.initials: PG
authors.lastname: Young
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology*; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics / Q000302:isolation & purification; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005784:Gene Amplification; D005800:Genes, Fungal; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology*; D018021:Lithium Chloride; D008961:Models, Structural; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011487:Protein Conformation; D015183:Restriction Mapping; D012568:Schizosaccharomyces / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers
chemical_list: D002352:Carrier Proteins; D002712:Chlorides; D004271:DNA, Fungal; D017923:Sodium-Hydrogen Exchangers; D012965:Sodium Chloride; D008094:Lithium; D012964:Sodium; D018021:Lithium Chloride