The Glycosylphosphatidylinositol-Anchored DFG Family Is Essential for the Insertion of Galactomannan into the β-(1,3)-Glucan-Chitin Core of the Cell Wall of Aspergillus fumigatus.

Laetitia Muszkieta,Jean-Paul Latgé,Rémi Beau,Gregory Jouvion,Lars-Oliver Essen,Jonathan Trow,Marian Samuel Vogt,Brendan P Cormack,Isabelle Mouyna,Thierry Fontaine

doi:10.1128/msphere.00397-19

Laetitia Muszkieta, Jean-Paul Latgé + Show 8 more

Open Access

https://doi.org/10.1128/msphere.00397-19

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Abstract

The fungal cell wall is a complex and dynamic entity essential for the development of fungi. It is composed mainly of polysaccharides that are synthetized by protein complexes. At the cell wall level, enzyme activities are involved in postsynthesis polysaccharide modifications such as cleavage, elongation, branching, and cross-linking. Glycosylphosphatidylinositol (GPI)-anchored proteins have been shown to participate in cell wall biosynthesis and specifically in polysaccharide remodeling. Among these proteins, the DFG family plays an essential role in controlling polar growth in yeast. In the filamentous fungus and opportunistic human pathogen Aspergillus fumigatus, the DFG gene family contains seven orthologous DFG genes among which only six are expressed under in vitro growth conditions. Deletions of single DFG genes revealed that DFG3 plays the most important morphogenetic role in this gene family. A sextuple-deletion mutant resulting from the deletion of all in vitro expressed DFG genes did not contain galactomannan in the cell wall and has severe growth defects. This study has shown that DFG members are absolutely necessary for the insertion of galactomannan into the cell wall of A. fumigatus and that the proper cell wall localization of the galactomannan is essential for correct fungal morphogenesis in A. fumigatusIMPORTANCE The fungal cell wall is a complex and dynamic entity essential for the development of fungi. It is composed mainly of polysaccharides that are synthetized by protein complexes. Enzymes involved in postsynthesis polysaccharide modifications, such as cleavage, elongation, branching, and cross-linking, are essential for fungal life. Here, we investigated in Aspergillus fumigatus the role of the members of the Dfg family, one of the 4 GPI-anchored protein families common to yeast and molds involved in cell wall remodeling. Molecular and biochemical approaches showed that DFG members are required for filamentous growth, conidiation, and cell wall organization and are essential for the life of this fungal pathogen.

Highlights

The fungal cell wall is a complex and dynamic entity essential for the development of fungi
The expression levels of the DFG genes seen during different stages of development of A. fumigatus were analyzed by quantitative real-time PCR (Fig. 1)
With the exception of DFG6, all of the DFG genes were expressed in the different fungal stages but their relative expression levels were highly dependent on the growth stage considered (Fig. 1)

Summary

Introduction

The fungal cell wall is a complex and dynamic entity essential for the development of fungi. Glycosylphosphatidylinositol (GPI)-anchored proteins have been shown to participate in cell wall biosynthesis and in polysaccharide remodeling. Among these proteins, the DFG family plays an essential role in controlling polar growth in yeast. IMPORTANCE The fungal cell wall is a complex and dynamic entity essential for the development of fungi. We investigated in Aspergillus fumigatus the role of the members of the Dfg family, one of the 4 GPI-anchored protein families common to yeast and molds involved in cell wall remodeling. It has prominent and dual roles during the growth of fungal pathogens. DFG multiple deletion resulted in the total loss of the cell wall galactomannan (GM), which was associated with severe growth phenotypes

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