A molecular vision of fungal cell wall organization by functional genomics and solid-state NMR

Arnab Chakraborty,Wenxia Fang,Jean-Paul Latgé,Malitha C Dickwella Widanage,Thierry Fontaine,Cheng Jin,Pingzhen Wei,Liyanage D Fernando,Tuo Wang

doi:10.1038/s41467-021-26749-z

Abstract

Vast efforts have been devoted to the development of antifungal drugs targeting the cell wall, but the supramolecular architecture of this carbohydrate-rich composite remains insufficiently understood. Here we compare the cell wall structure of a fungal pathogen Aspergillus fumigatus and four mutants depleted of major structural polysaccharides. High-resolution solid-state NMR spectroscopy of intact cells reveals a rigid core formed by chitin, β-1,3-glucan, and α-1,3-glucan, with galactosaminogalactan and galactomannan present in the mobile phase. Gene deletion reshuffles the composition and spatial organization of polysaccharides, with significant changes in their dynamics and water accessibility. The distribution of α-1,3-glucan in chemically isolated and dynamically distinct domains supports its functional diversity. Identification of valines in the alkali-insoluble carbohydrate core suggests a putative function in stabilizing macromolecular complexes. We propose a revised model of cell wall architecture which will improve our understanding of the structural response of fungal pathogens to stresses.

Highlights

Vast efforts have been devoted to the development of antifungal drugs targeting the cell wall, but the supramolecular architecture of this carbohydrate-rich composite remains insufficiently understood
The solid-state NMR analysis of A. fumigatus cell wall has suggested that α-1,3-glucans are spatially packed with chitin and are likely distributed in a soft and hydrated matrix formed by diversely linked β-glucans[15], whereas the chemical data suggested that α-1,3-glucan and chitin were separated based on their differential alkali-solubility
It is quite common that a single type of polysaccharides could possibly have mobile domains that are present in the soft matrix and rigid phases that are physically packed with stiff molecules such as the cellulose microfibrils in plants and the chitin molecules in fungi[15,29]

Summary

Introduction

Vast efforts have been devoted to the development of antifungal drugs targeting the cell wall, but the supramolecular architecture of this carbohydrate-rich composite remains insufficiently understood. Solid-state NMR spectroscopy has been employed to characterize the molecular architecture of cell walls and melanin deposition in multiple fungal species including A. fumigatus, Cryptococcus neoformans, and Schizophyllum commune[15,16,17,18,19,20]. It is essential to reconcile the NMR-restrained structure and the model based on biochemical analysis[12,15] For this purpose, we coupled NMR studies with a functional genomics approach using A. fumigatus cell wall mutants that have been characterized previously using chemical methods. The parental strain is ΔakuBKU80, which is a widely used model strain a Chitin (Ch)

Methods

Results

Conclusion