trans-dominant mutations in the GPR1 gene cause high sensitivity to aceticacid and ethanol in the yeast Yarrowia lipolytica

Acetate non-utilizing strains harbouring trans-dominant mutations in the GP R1 gene (GPR1(d)) of the dimorphic yeast Yarrowia lipolytica have been sele cted and characterized. These mutants are highly sensitive to low concentra tions of acetic acid and ethanol, even in presence of glucose. The toxic ef fect of acetic acid is pi-I-dependent and has the strongest effect at low p H. In contrast, the action of ethanol is pH-independent. One GPR1(d) mutant has been detected that was highly sensitive to acetic acid but could still grow on ethanol, which indicates putative differences in the function of t he GPR1 gene product in the sensitivity to acetic acid and ethanol. The GPR 1(d) mutants exhibit a complex pleiotropic phenotype. The mutations cause c hanged colony morphology as well as dimorphism of cells, and induce early c ell death during growth on glucose, even without the presence of dicarbon c ompounds. Composition of intracellular membranes, as well as morphology of vacuole and mitochondria, were strongly changed. Back-crosses with wild-typ e strains and analysis of recombinant strains have shown that the expressio n of the pleiotropic phenotype depends on the site of mutation in the GPR1 gene, as well as on the genetic background of the strain harbouring the res ponsive mutation. Our data suggest that Gpr1p is involved in a general resp onse of cells to the toxic action of dicarbon compounds like acetic acid an d ethanol. Copyright (C) 1999 John Wiley & Sons, Ltd.