Fungal Cell Walls

Abstract

Fungal cell walls are paradoxical combinations of unyielding rigidity and soft elastic plasticity, inert protective covers and dynamic regulators of metabolism and differentiation, impenetrable hydrophobic layers and freely secreting tips, about which all too little is understood.

Keywords: chitin; glucans; hyphal tip structure; wall biosynthesis; wall interactions; hyphal form

Figure 1.

Model of wall structure at apex, lateral walls and branch points. Different kinds of microvesicles are produced by the Golgi bodies and transported to the apex (a) and branch sites (b) on cytoskeletal elements: microfilaments (beaded lines) and microtubules (parallel lines). The vesicles accumulate at the apex to form the Spitzenkörper. Enzymes, such as chitin and glucan synthases, contained in the vesicles (solid circles) become incorporated in the cell plasma membrane or released into the wall area by fusion of the vesicles with the plasma membrane. Other vesicles (open circles) may contain matrix components and other materials needed for wall biosynthesis and structure. In the apical dome the chitin and β‐(1‐3)‐glucans become more crystalline by hydrogen bonding and become progressively more crosslinked by the formation of covalent bonds (black dots) as the wall matures. Branch formation requires the redirection or localized accumulation of vesicles containing both wall softening (lytic) enzymes and synthases. Turgor pressure is assumed to push out the weakened wall, but cytoskeletal elements may also play an important role in branch formation. Modified with permission from Gooday GW (1995) Cell walls. In: Gow NAR and Gadd GM (eds) The Growing Fungus, pp. 43–62. London: Chapman and Hall. Copyright © 1995 Plenum Publishers.

Figure 2.

Major cell wall structural components. Cellulose and chitin are straight‐chain polymers, able to form parallel strands that become almost crystalline. β‐glucans (a β‐(1,3) chain with β‐(1,6) branches) can form complex interlinked structures with other glucans and glycoproteins.

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References

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Further Reading

Bartnicki‐Garcia S, Bartnicki DD and Gierz G (1995) Determinants of fungal cell wall morphology – the vesicle supply center. Canadian Journal of Botany 73(supplement): s372–s378.

Calderone RA (1993) Molecular interactions at the interface of Candida albicans and host cells. Archives of Medical Research 24: 275–279.

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Gow NAR and Gadd GM (1995) The Growing Fungus. London: Chapman and Hall.

Hamer JE, Howard RJ, Chumley FG and Valent B (1988) A mechanism for surface attachment of spores of a plant pathogenic fungus. Science 239: 288–290.

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Pramanik A, Martin EZ, Mckoy JF et al. (1995) A mutant approach and molecular strategy to study fungal cell walls. Cellular and Molecular Biology 41 (supplement): s73–s81.

Thomas D des S and Mullins JT (1967) Role of enzymatic wall‐softening in plant morphogenesis: hormonal induction in Achlya. Science 156: 84.

Wessels JGH (1994) Developmental regulation of fungal cell wall formation. Annual Review of Phytopathology 32: 413–437.

Wheeler MH and Bell AA (1988) Melanins and their importance in pathogenic fungi. Current Topics in Medical Mycology 2: 338–387.

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Ross, Ian K(Dec 2001) Fungal Cell Walls. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0000355]