Glucan structure in a fragile mutant of Saccharomyces cerevisiae

Abstract

The phenotype of VY1160 fragile Saccharomyces cerevisiae mutant is characterized by cell lysis upon transfer to hypotonic solutions and increased permeability of cells growing in osmotically stabilized media. Two mutations, srb1 and ts1, have been identified in VY1160 cells and previous studies have shown that the increased permeability is due to the ts1 mutation which causes a shortening of mannan side-chains. Here we report that the srb1 mutation, which is the genetic determinant of cell lysis, is responsible for quantitative and structural changes of glucans. Experiments with isogenic single mutation strains, genetic studies coupled with quantitative measurements of glucan content per cell, and methylation analysis of glucans provide evidence that srb1 mutation leads to i) formation of mechanically unstable cell wall network made of insoluble glucan fibrils which are shorter and contain beta(1-6) inter-residue linkages and ii) insufficient filling of the space between the fibrils due to a shortage of the alkali-soluble glucan. Although growing exponentially in osmotically stabilized media, the srb1 cells cannot resist an osmotic shock and, hence, burst immediately.

Papulacandin B resistance in budding and fission yeasts: isolation and characterization of a gene involved in (1,3)beta-D-glucan synthesis in Saccharomyces cerevisiae

“…Other types of screenings directed more specifically towards the detection of ␤-glucan-defective mutants have been undertaken. In some cases, the aim has been to isolate osmotically fragile mutants defective in ␤-glucan synthesis in S. cerevisiae (4,36) and in Schizosaccharomyces pombe (52). In this way, S. pombe mutants affected either directly or indirectly in the particulate or in the detergent-solubilized component of (1,3)␤-D-glucan synthase have been isolated (14,52).…”

Non-wasteful fractionation of fragile yeast cells for the production of nutritional protein and other by-products

“…As shown in Table 1, S. cerevisiae 211 cells contained 51% protein and 7% nucleic acids. Its polysaccharide content (23%) was lower compared to other strains, which is due to the decreased contents of manoproteins and alkali-soluble glucan found in previous analytical determinations of cell wall components of the fragile S. cerevisiae mutants [15,16]. Unlike any other strain, however, S. cerevisiae 211 produced biomass with a very high degree of digestability.…”

Suppression of sorbitol dependence in a strain bearing a mutation in the SRB1/PSA1/VIG9 gene encoding GDP-mannose pyrophosphorylase by PDE2 overexpression suggests a role for the Ras/cAMP signal-transduction pathway in the control of yeast cell-wall biogenesis

“…Work on strains carrying the srb1-1 mutation found a number of cell-wall changes, including alterations in glucan structure and composition (Blagoeva et al, 1991), and mannan content (Maerkisch et al, 1983). Investigations on the mode of action of actinomycin D (Waltschewa et al, 1976) and rifampicin (Venkov et al, 1975) have been facilitated by the hypersensitivity to antibiotics shown by strains carrying the srb1-1 mutation.…”

“…Additional phenotypes include the ability to lyse upon hypotonic shock, antibiotic hypersensitivity and increased permeability of the cell wall and membrane due to defects in their structure and composition (Maerkisch et al, 1983 ;Blagoeva et al, 1991 ;Kopecka et al, 1991). In a previous study (Stateva et al, 1991), a yeast chromosomal gene was isolated that complemented sorbitol dependence in a number of srb strains, including 4STLU.…”