The structure and synthesis of the fungal cell wall

Abstract

The fungal cell wall is a dynamic structure that protects the cell from changes in osmotic pressure and other environmental stresses, while allowing the fungal cell to interact with its environment. The structure and biosynthesis of a fungal cell wall is unique to the fungi, and is therefore an excellent target for the development of anti-fungal drugs. The structure of the fungal cell wall and the drugs that target its biosynthesis are reviewed. Based on studies in a number of fungi, the cell wall has been shown to be primarily composed of chitin, glucans, mannans and glycoproteins. The biosynthesis of the various components of the fungal cell wall and the importance of the components in the formation of a functional cell wall, as revealed through mutational analyses, are discussed. There is strong evidence that the chitin, glucans and glycoproteins are covalently cross-linked together and that the cross-linking is a dynamic process that occurs extracellularly.

The decomposition of ectomycorrhizal fungal necromass

“…Once viewed as a static structure, the cell wall is now known to be a highly dynamic structure with its composition varying depending on factors such as age, genotype, taxon, and environment (Bartnicki-Garcia, 1968;Wessels, 1994;Bowman and Free, 2006;Feofilova, 2010). EM fungi, which are primarily members of the Basidiomycota and Ascomycota, have cell walls that are composed of b-glucans, chitin, proteins and melanins, along with other minor components (Wessels, 1994;Bowman and Free, 2006;Feofilova, 2010). There is wide variation in the decomposition rates of fungal cells among species (Hurst and Wagner, 1969) due to variation in the proportion of the cell wall comprising glucans, chitin, protein and melanin.…”

“…Chitin is composed of n-acetylglucosamine monomers with b-(1,4) linkages and represents a significant source of C and N in many ecosystems. Concentrations of chitin as high as 20e30% of dry weight have been found in some filamentous fungi (Bowman and Free, 2006), but chitin concentrations in EM fungi typically range from 1 to 10% of dry weight (Ekblad et al, 1998;Markkola et al, 2002;Fernandez and Koide, 2012).…”

Genome-wide analysis of cell wall-related genes in Tuber melanosporum

“…Chitin synthases (EC 2.4.1.16) belong to a gene family that can be divided into several classes with specific roles, as demonstrated in several fungi through genetic analyses (Bowman and Free 2006). Six genes coding for "standard" chitin synthases (TmelCHSD, TmelCHS2, TmelCHS3, TmelCHS4, TmelCHS7 and TmelCHSG) and two genes coding for myosin-chitin synthases (TmelCHS6 and TmelCHS8) were identified in T. melanosporum and, as revealed by phylogenetic analysis, all the CHS classes seem to be represented by at least one member in T. melanosporum, except class III for which two members are present (Fig.…”

“…In addition to maintaining cell shape and integrity during environmental stress, the cell wall is also involved in the interaction with its surroundings and serves as a signaling center to activate signal transduction pathways within fungal cells (Bowman and Free 2006). The fungal cell wall is usually composed of chitin, glucans and proteins that are extensively cross-linked together to form a complex network, which forms the structural basis of the cell wall (Bowman and Free 2006). However, the composition varies from taxonomic group to taxonomic group and may also vary within a single fungal isolate, depending on the conditions and the stage of growth.…”

“…A cell wall in fact undergoes constant changes, i.e., during cell expansion and division in yeasts, and during spore germination, branching and septum formation in filamentous fungi. The formation and remodeling of the fungal cell wall involves numerous biosynthetic pathways and the concerted actions of many gene products (Bowman and Free 2006). Although the yeast cell wall structure and assembly is considered as a general model (Lesage and Bussey 2006), recent results, derived from wholegenome analysis of other fungi, have highlighted a number of differences between filamentous fungi and yeast.…”