Intracellular
sodium distribution in the halotolerant yeast Debaryomyces hansenii. Identification of
the DhNHX1
gene.
Vera Montiel,
Jose Ramos
Microbiology, University of Cordoba, Campus Rabanales C6, Cordoba, 14071, Spain
(g52modiv@uco.es)
Sodium is a toxic element for most yeast cells. Several strategies have been described in order to reduce the cytoplasmatic sodium concentration, and consequently its toxic effects in Saccharomyces cerevisiae. One of these actions is sodium accumulation into the vacuole. Debaryomyces hansenii is a halotolerant yeast. This organism lives in salty environments like sea water. We think that the study of this yeast can be very interesting to understand the physiological and genetics bases of salt tolerance. In fact, we propose that the mechanisms of sodium tolerance in D. hansenii could be different than those present in S. cerevisiae. A first approach to the study of the vacuolar role in the halotolerance of D hansenii indicates the existence of a sodium transporter, involved in sodium accumulation in this organelle. This process would reduce the sodium concentration in the cytoplasm, regulating the possible toxicity of this cation in the cell. In other organisms sodium sequestration is controlled by the NHX and NHE systems. By using the conserved areas in the sequence of these genes we have designed degenerated primers and we have identified and sequenced one gene named DhNHX1. Results indicating that this gene is most probably involved in vacuolar sodium transport though the vacuole will be presented.