Regulation of chitin synthesis during dimorphic growth of Candida albicans

Abstract

Candida albicans has three genes encoding chitin synthase enzymes. In wildtype strains, the expression of CHS2 and CHS3 peaked 1-2 h after the induction of hyphal growth, whilst mRNA levels in a non-germinative strain, CA2, remained low under the same conditions. CHSl gene expression did not peak during germ tube formation but remained a t low levels in both yeast and hyphal growth. The pattern of gene expression did not predict the changes in measured chitin synthase activities or changes in chitin content during dimorphic transition. Chitin synthase activity increased steadily, and did not peak shortly after germ tube induction, and activity profiles were similar in germ-tube-competent and germ-tube-negative strains. The phenotype of a Achs2 null mutant suggested that CHS2 encoded the major enzyme activity in vitro and was largely responsible for elevated chitin synthase activities in microsomal preparations from hyphal cells compared to yeast cells. However, CaChs3p was responsible for synthesis of most chitin in both yeast and hyphae. Three independent chitin assays gave markedly different estimates of the relative chitin content of yeast and hyphae and wild-type and chs mutants. Only one of the methods gave a significantly higher chitin content for hyphal compared to yeast cell walls and a lower chitin content for hyphae of the Achs2 null mutant compared to the parental strain.

Deletion of PDE2, the gene encoding the high‐affinity cAMP phosphodiesterase, results in changes of the cell wall and membrane in Candida albicans

“…Remarkably, the changes in the cell wall composition were demonstrated during hyphal growth as well. No increase in chitin level, which normally occurs in hyphal cell walls (Munro et al, 1998;Sullivan et al, 1983), was observed (Table 5). This is consistent with earlier observation of the inability of the pde2 null mutant to form normal hyphae in liquid media in response to serum and, indeed, to other hyphal inducers (Jung and Stateva, 2003).…”

Cell wall stress induces alternative fungal cytokinesis and septation strategies

“…Therefore, we used time lapse video-microscopy to determine whether inhibition of different classes of chitin synthase affected the localization of Chs3-YFP. RO-09-3143 was used to inhibit Chs1, and nikkomycin Z to preferentially inhibit the class I enzymes, Chs2 and Chs8 (Gaughran et al, 1994;Munro and Gow, 1995;Munro et al, 1998). …”

“…Null mutants lacking Chs3 are viable but have very low cell wall chitin contents (Bulawa et al, 1995). Chs2 and Chs8 account for .90% of in vitro chitin synthase activity (Gow et al, 1994;Munro et al, 1998;Munro et al, 2003), are normally non-essential, but are strongly upregulated in response to cell wall stress such as treatment with echinocandin antifungals Walker et al, 2008).…”

Chemical reactivity and antimicrobial activity of N-substituted maleimides

“…Chitin synthase activity was determined in MMF of C. albicans cells by the method of Munro et al 17 The MMFs were activated by 5-min incubation with 100 ng trypsin μl −1 MMF at 30°C and the reactions were stopped by addition of 150 ng soybean trypsin inhibitor μl range). Incubations were carried out at 30°C for 30 min and the reaction was stopped by addition of 1 ml of 66% (v/v) ethanol.…”