The linkage of (1–3)‐β‐glucan to chitin during cell wall assembly in Saccharomyces cerevisiae

Pulse‐chase experiments with [14C]glucose demonstrated that in the cell wall of wild‐type Saccharomyces cerevisiae alkali‐soluble (1–3)‐β‐glucan serves as a precursor for alkali‐insoluble (1–3)‐β‐glucan. The following observations support the notion that the insolubilization of the glucan is caused by linkage to chitin: (i) degradation of chitin by chitinase completely dissolved the glucan, and (ii) disruption of the gene for chitin synthase 3 prevented the formation of alkali‐insoluble glucan. These cells, unable to form a glucan–chitin complex, were highly vulnerable to hypo‐osmotic shock indicating that the linkage of the two polymers significantly contributes to the mechanical strength of the cell wall. Conversion of alkali‐soluble glucan into alkali‐insoluble glucan occurred both early and late during budding and also in the ts‐mutant cdc24‐1 in the absence of bud formation.