The Role of Tryptophan Permease Tat2 in Cell Growth of Yeast under High-Pressure Condition

Abstract

When growing cells of the yeast Saccharomyces cerevisiae are subjected to hydrostatic pressure in the range of 15–25 MPa, tryptophan uptake via the high-affinity tryptophan permease Tat2 is down-regulated leading to arrest of the cell cycle in the G1 phase. Tat2 protein level analyzed by Western blot decreased during incubation of the cells at 25 MPa. Interestingly, overexpression of TAT2 gene on a multicopy plasmid conferred high-pressure growth on the wild-type cells as well as low-temperature growth. Increasing pressure is similar with decreasing temperature in terms of decrease in membrane fluidity. Therefore, the uptake of tryptophan may be the cellular process most sensitive to decrease in membrane fluidity, which is caused by either increasing pressure or decreasing temperature. We isolated mutants capable of growth at pressures of 15–25 MPa. These strains also grew at low-temperature condition of 15 °C. One of the mutants, designated as HPG1, expressed abundant Tat2 at both 0.1 and 25 MPa. In this paper, we describe evidence that Tat2 has an essential role in high-pressure growth in yeast.