Temperature-sensitive Saccharomyces cerevisiae mutant defective in lipid biosynthesis

Abstract

A temperature-sensitive mutant of Saccharomyces cerevisiae (DAM303) is described that exhibits an early defect in lipid biosynthesis at the restrictive growth temperature, 37°C. This strain rapidly lost viability after 1 h of incubation at 37°C, and this was accompanied by a significantly reduced incorporation of 32P(i) into cellular lipid and an accumulation of [1-14C]acetate into the free fatty acid fraction. The temperature-sensitive DAM303 mutation failed to complement the sec13 mutation described by Novick et al., and from analysis of invertase secretion in the temperature-sensitive DAM303 strain, it is clear that the loss of invertase secretion in the mutant occurs after the loss of phospholipid synthesis. Although the precise nature of the temperature-sensitive lesion in the DAM303 strain has still to be identified, the results from the study of this mutant indicate that a defect in lipid biosynthesis can be correlated with subsequent alterations in extracellular protein secretion and loss of other macromolecular functions including DNA, RNA, and protein synthesis. From studies of this mutant, two procedures of enriching for other temperature-sensitive mutants with defects in lipid biosynthesis have emerged: inositol overproduction and screening for increased buoyant densities.