Differential cell wall remodeling of two chitin synthase deletants Delta chs3A and Delta chs3B in the pathogenic yeast Candida glabrata

摘要

It is known that cell wall remodeling and the salvaging pathway act to compensate for an impaired or a damaged cell wall. Lately, it has been indicated that this mechanism is partly required for resistance to the glucan synthesis inhibitor echinocandin. While cell wall remodeling has been described in mutants of glucan or mannan synthesis, it has not yet been reported in a chitin synthesis mutant. Here, we describe a novel cell wall remodeling and salvaging pathway in chitin synthesis mutants, Delta chs3A and Delta chs3B, of the pathogenic yeast Candida glabrata. Electron microscopic analysis revealed a thickened mannoprotein layer in Delta chs3A cells and a thickened chitin-glucan layer of Delta chs3B cells, and it indicated the hypothesis that mannan synthase and chitin-glucan synthase indemnify Delta chs3A and Delta chs3B cells, respectively. The double-mutant CHS3A and MNN10, encoding alpha-1,6-mannosyltransferase, showed synergistic stress sensitization, and the Delta chs3B strain showed supersensitivity to echinocandins. Hence, these findings support the above hypothesis of remodeling. Furthermore, unlike Delta chs3A cells, Delta chs3B cells showed supersensitivity to calcineurin inhibitor FK506 and Tor1p kinase inhibitor rapamycin, indicating that the Delta chs3B strain uses the calcineurin pathway and a Tor1p kinase for cell wall remodeling.