A GLUTAMINE-SYNTHETASE MUTANT OF SACCHAROMYCES-CEREVISIAE SHOWS DEFECT IN CELL-WALL

To study the organization and biosynthesis of the yeast cell wall, hyp o-osmolarity-sensitive mutants of Saccharomyces cerevisiae were analyz ed. Cells of JS4 were irregular in shape and fragile. Calcofluor stain ing and quantitative analysis indicated that the chitin content was re duced. By DNA cloning and genetic analysis, the mutation hpo1-1 was fo und to be allelic to GLN1 which encodes glutamine synthetase. The glut amine content was significantly low in JS4, and the mutant was recover ed from the cell wall defect by supplying glutamine in the medium. Par tial inhibition of glutamine synthetase by phosphinothricin also induc ed defects in the cell wall. These results indicate that the shortage of glutamine affects cell wall integrity prior to other cellular funct ions.