Abstract
The spore wall of Saccharomyces cerevisiae is a multilaminar extracellular structure that is formed de novo in the course of sporulation. The outer layers of the spore wall provide spores with resistance to a wide variety of environmental stresses. The major components of the outer spore wall are the polysaccharide chitosan and a polymer formed from the di-amino acid dityrosine. Though the synthesis and export pathways for dityrosine have been described, genes directly involved in dityrosine polymerization and incorporation into the spore wall have not been identified. A synthetic gene array approach to identify new genes involved in outer spore wall synthesis revealed an interconnected network influencing dityrosine assembly. This network is highly redundant both for genes of different activities that compensate for the loss of each other and for related genes of overlapping activity. Several of the genes in this network have paralogs in the yeast genome and deletion of entire paralog sets is sufficient to severely reduce dityrosine fluorescence. Solid-state NMR analysis of partially purified outer spore walls identifies a novel component in spore walls from wild type that is absent in some of the paralog set mutants. Localization of gene products identified in the screen reveals an unexpected role for lipid droplets in outer spore wall formation.
Highlights
All cells surround themselves with some form of extracellular matrix that provides structural integrity to the cell and protection from the environment
Using a genetic approach we reveal a network of genes that function redundantly to control dityrosine layer synthesis
Solid state nuclear magnetic resonance (NMR) analysis of spore walls from wild-type and mutant cells reveals a novel constituent of the spore wall that may link the dityrosine to the underlying polysaccharides and a role for lipid droplets in the incorporation of this new component into the spore wall
Summary
All cells surround themselves with some form of extracellular matrix that provides structural integrity to the cell and protection from the environment. The extracellular matrix is referred to as the cell wall and serves as the interface between a fungal cell and its environment. The vegetative cell wall of Saccharomyces cerevisiae has been used extensively as a model for studies of fungal cell walls, though it lacks components such as the polyphenols that are found in other fungi [3]. These constituents are found, in the wall of S. cerevisiae spores
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