Abstract
The yeast cell is surrounded by a cell wall conferring protection and resistance to environmental conditions that can be harmful. Identify the molecular cues (genes) which shape the biochemical composition and the nanomechanical properties of the cell wall and the links between these two parameters represent a major issue in the understanding of the biogenesis and the molecular assembly of this essential cellular structure, which may have consequences in diverse biotechnological applications. We addressed this question in two ways. Firstly, we compared the biochemical and biophysical properties using atomic force microscopy (AFM) methods of 4 industrial strains with the laboratory sequenced strain BY4743 and used transcriptome data of these strains to infer biological hypothesis about differences of these properties between strains. This comparative approach showed a 4–6-fold higher hydrophobicity of industrial strains that was correlated to higher expression of genes encoding adhesin and adhesin-like proteins and not to their higher mannans content. The second approach was to employ a multivariate statistical analysis to identify highly correlated variables among biochemical, biophysical and genes expression data. Accordingly, we found a tight association between hydrophobicity and adhesion events that positively correlated with a set of 22 genes in which the main enriched GO function was the sterol metabolic process. We also identified a strong association of β-1,3-glucans with contour length that corresponds to the extension of mannans chains upon pulling the mannosyl units with the lectin-coated AFM tips. This association was positively correlated with a group of 27 genes in which the seripauperin multigene family was highly documented and negatively connected with a set of 23 genes whose main GO biological process was sulfur assimilation/cysteine biosynthetic process. On the other hand, the elasticity modulus was found weakly associated with levels of β-1,6-glucans, and this biophysical variable was positively correlated with a set of genes implicated in microtubules polymerization, tubulin folding and mitotic organization.
Highlights
The yeast Saccharomyces cerevisiae is surrounded by a 100–150 nm thick armor termed the cell wall which amounts to 10–25% of the cell dry mass (Aguilar-Uscanga and Francois, 2003; Yin et al, 2007)
The dynamic nature of the cell wall is witnessed by the ability of yeast cell to show important morphogenetic modifications and to adapt to environmental stress or various injuries caused by drugs, lytic enzymes as well as mutations that cause defect in genes implicated in its synthesis
Among them were identified several genes encoding glycosyltransferase/hydrolase, that were called “cell wall remodeling enzymes.”. These changes at the transcriptional level can be associated with biochemical modifications that take place in response to cell wall remodeling and which are: (i) an increase of chitin amount in cell wall which can contribute up to 20% of the cell wall when important genes encoding for its biosynthesis are deleted; (ii) a modification of linkages between cell wall components and (iii) an increase of cell wall remodeling enzymes accompanied with a redistribution of cell wall synthesis and repair machinery (Klis et al, 2006; Orlean, 2012)
Summary
The yeast Saccharomyces cerevisiae is surrounded by a 100–150 nm thick armor termed the cell wall which amounts to 10–25% of the cell dry mass (Aguilar-Uscanga and Francois, 2003; Yin et al, 2007). The fuzzy electron dense outer layer of about 30–40 nm thick is supposed to mainly contain cell wall mannoproteins, whereas the internal layer of about 70–100 nm that shields the plasma membrane is mainly made of β-glucans (Osumi, 1998; Backhaus et al, 2010; Schiavone et al, 2016). In spite of these apparent distinct layers, the four macromolecules that composed the cell wall, namely mannoproteins, β-1, 3 glucans, β-1,6 glucans and chitin are covalently joined to generate a highly dynamic three-dimensional architecture of the wall. Among them were identified several genes encoding glycosyltransferase/hydrolase, that were called “cell wall remodeling enzymes.” These changes at the transcriptional level can be associated with biochemical modifications that take place in response to cell wall remodeling and which are: (i) an increase of chitin amount in cell wall which can contribute up to 20% of the cell wall when important genes encoding for its biosynthesis are deleted; (ii) a modification of linkages between cell wall components and (iii) an increase of cell wall remodeling enzymes accompanied with a redistribution of cell wall synthesis and repair machinery (Klis et al, 2006; Orlean, 2012)
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