Intracellular Na and K distribution in Debaryomyces hansenii. Cloning and expression in Saccharomyces cerevisiae of DhNHX1.
Debaryomyces hansenii is a salt-tolerant yeast that contains high amounts of internal Na(+). Debaryomyces hansenii kept more sodium than Saccharomyces cerevisiae in both the cytoplasm and vacuole when grown under a variety of NaCl concentrations. These results indicate a higher tolerance of Debaryomyces to high internal Na(+), and, in addition, suggest the existence of a transporter driving Na(+) into the vacuole. Moreover, a gene encoding a Na(+) (K(+))/H(+) antiporter from D. hansenii was cloned and sequenced. The gene, designated DhNHX1, exhibited significant homology with genes of the NHE/NHX family. DhNHX1 expression was induced neither at low pH nor by extracellular NaCl. A mutant of S. cerevisiae lacking its own Na(+) transporters (ena1-4Delta nha1 Delta nhx1 Delta), when transformed with DhNHX1, partially recovered cation tolerance as well as the ability to accumulate Na(+) and K(+) into the vacuole. Our analysis provides evidence that DhNhx1p transports Na(+) (and K(+)) into the vacuole and that it can play an important role in ion homeostasis and salt tolerance.
Montiel
Vera
V
Laboratorio de Microbiología Agrícola, Departamento de Microbiología, Universidad de Córdoba, Córdoba, Spain.
Ramos
José
J
D000595:Amino Acid Sequence; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D011188:Potassium / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D004718:Saccharomycetales / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D012964:Sodium / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D027682:Cation Transport Proteins; D005656:Fungal Proteins; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D011188:Potassium