Deletion of MCD4 involved in glycosylphosphatidylinositol (GPI) anchor synthesis leads to an increase in β-1,6-glucan level and a decrease in GPI-anchored protein and mannan levels in the cell wall of Saccharomyces cerevisiae

Most proteins involved in the synthesis of the GPI core structure of Saccharomyces cerevisiae are essential for growth. To explore the relationship between the GPI anchor structure and β-1,6-glucan synthesis, we screened deletion mutants in genes involved in GPI synthesis for osmotic remedial growth. Heterozygous diploid strains were dissected on medium with osmotic support and slow growth of the mcd4 deletion mutant was observed. The mcd4 mutant showed abnormal morphology and cell aggregation, and was hypersensitive to SDS, hygromycin B and K1 killer toxin. Incorporation of GPI cell wall proteins was examined using a GPI-Flo1 fusion protein. The result suggested that the mcd4 deletion causes a decrease in GPI cell wall proteins levels. The mutation also caused a decrease in mannan levels and an increase in alkali-insoluble β-1,6-glucan and chitin levels in the cell wall.