Formation of a New Cell Wall by Protoplasts of Candida albicans: Effect of Papulacandin B, Tunicamycin and Nikkomycin

Abstract

Incorporation of polysaccharides into the walls of regenerating protoplasts of Candida albicans was followed in the presence of papulacandin B, tunicamycin and nikkomycin. With the first drug, chitin was incorporated normally whereas incorporation of glucans and mannoproteins was significantly decreased. Tunicamycin decreased incorporation of all wall polymers when added at the beginning of the regeneration process but blocked only mannan and alkaliinsoluble glucan incorporation when added after 5 h. Nikkomycin inhibited chitin synthesis, and the walls formed by the protoplasts were enriched in alkali-soluble glucan. Pulse-chase experiments suggested that a precursor-product relationship between the alkali-soluble and alkali-insoluble glucans existed in the wall. The results obtained with the antibiotics were confirmed and extended by cytological studies using wheat-germ agglutinin labelled with colloidal gold and concanavalin A-ferri tin as specific markers of chitin and mannoproteins respectively. The results support the idea that regeneration of walls by protoplasts occurs in two steps : firstly, a chitin microfibrillar skeleton is formed, and in a later step glucan-mannoprotein complexes are added to the growing structure. The chitin skeleton probably allows the orderly spatial arrangement of the other polymers giving rise to the regenerated cell wall.

Genomic response programs of Saccharomyces cerevisiae following protoplasting and regeneration

“…An important difference observed in the process occurring in both organisms was that the number of up-regulated genes related to cell wall synthesis and structure, and their corresponding expression, values that were significantly higher in C. albicans (Castillo et al, 2006). Also a noticeable difference was the observation that the up-regulated C. albicans genes involved in cell wall synthesis and structure increased their expression at different periods, and normally decayed (Castillo et al, 2006), following approximately the kinetics of the deposition of the corresponding polymers in the growing wall (see Elorza et al, 1987Elorza et al, , 1994Murgui et al, 1986). In contrast, up-regulated genes during regeneration of S. cerevisiae protop- lasts reached their highest values almost simultaneously after 2 h of incubation.…”

Wall Mannoproteins of the Yeast and Mycelial Cells of Candida albicuns: Nature of the Glycosidic Bonds and Polydispersity of Their Mannan Moieties

“…The physiological significance of the very high polydispersity of the wall mannoproteins is totally unknown. The observations that (i) changes in a single sugar residue affect the overall conformation of a macromolecule, and (ii) the carbohydrate moiety of glycoconjugates changes during development, differentiation and transformation (Stanley, 1987), point to the important functional role of mannoproteins in controlling the cell wall structure (Murgui et al, 1986;Elorza et al, 1987).…”

Genomic response programs of Candida albicans following protoplasting and regeneration

“…The protoplasts of C. albicans are devoid of wall (Miragall et al, 1988) and regeneration is initiated by deposition of chitin followed by laying of glucan molecules that complement a network allowing incorporation of mannoproteins by covalent bonds (Miragall et al, 1986;Elorza et al, 1987). Interestingly enough, the nature of the protein complexes initially released by -glucases are diVerent from those extracted from growing cells (Elorza et al, 1994;Murgui et al, 1986).…”