Systematic Mapping of cell Wall Mechanics in the Regulation of Cell Morphogenesis

Abstract

Walled cells of plants, fungi and bacteria, come with a large range of shapes and sizes, which are ultimately dictated by the mechanics of their cell wall. This stiff and thin polymeric layer encases the plasma membrane and protects the cells mechanically by opposing large turgor pressure derived stresses. To date, however, we still lack a quantitative understanding for how local and/or global mechanical properties of the wall support cell morphogenesis. Here, we combine super-resolution imaging, and laser-mediated wall relaxation, to quantitate subcellular values of wall thickness (h) and bulk elastic moduli (Y) in large populations of live mutant cells and conditions affecting cell diameter in the rod-shaped model fission yeast.We find that lateral wall stiffness, defined by the surface modulus, σ=hY, robustly scales with cell diameters. This scaling is valid in tens of mutants covering various functions, within the population of individual isogenic strains, along single misshaped cells, and even across the fission yeasts clade. Dynamic modulations of cell diameter by chemical and/or mechanical means suggest that the cell wall can rapidly adapt its surface mechanics, rendering stretched wall portions stiffer than unstretched ones. Size-dependent wall stiffening constrains diameter definition and limits size variations, and may also provide and efficient mean to keep elastic strains in the wall below failure strains potentially promoting cell survival. This quantitative set of data impacts our current understanding of the mechanics of cell walls, and its contribution to morphogenesis.

An image analysis method to survey the dynamics of polar protein abundance in the regulation of tip growth

“…One interesting feature of the WT growth pattern, is that the new end never reaches the same growth speed as the old end (Figure 1D) (Mitchison and Nurse, 1985). We envisaged three putative scenarios for this: (i) the cell cycle length may not be long enough for the new end to reach the growth speed of the old end; (ii) this difference could be caused by a particular biochemistry and/or mechanics at the new end inherited from the septum (Atilgan et al, 2015;Davi et al, 2019), or (iii) that the two tips continuously compete for a limited pool of growth promoting components, and the earlier take off of the old end segregates an initial pool at the expense of the new end, preventing it to reach the same speed.…”

“…Turgor is thought to power growth by pushing and deforming freshly synthesized cell wall; and drastic reduction of pressure can halt growth instantaneously (Bastmeyer et al, 2002;Haupt et al, 2018;Lew, 2011;Minc et al, 2009). Because turgor is isotropic, polarized remodeling of the cell wall may render it thinner and softer thereby restricting its expansion to cell tips (Abenza et al, 2015;Davi et al, 2019;Davì et al, 2018).…”

Inferring relative surface elastic moduli in thin-wall models of single cells

“…As for single plant cells, the bulk modulus of cells = P/ dV V has been measured in various systems [8][9][10] by manipulating the pressure P inside the cell while tracking the fraction change in the cell volume dV V . Recently in fission yeast [11][12][13], the cell-wall elastic property is distinguished from the cell bulk, where the cell wall is assumed to be elastic in the lateral directions along the wall surface. The surface elastic constants such as Young's modulus and Poisson's ratio ν have been inferred by measuring the elastic strains along the wall surface and applying Young-Laplace's Law, which connects the local surface curvature with the lateral tensions and the turgor pressure.…”

“…The surface elastic constants such as Young's modulus and Poisson's ratio ν have been inferred by measuring the elastic strains along the wall surface and applying Young-Laplace's Law, which connects the local surface curvature with the lateral tensions and the turgor pressure. In [13],…”

BRITTLE PLANT1 is required for normal cell wall composition and mechanical strength in rice

“…Susceptibility to lodging is a key limiting factor in cereal crop production. Culm strength, which depends largely on the thickness, composition, and arrangement of the polysaccharide network of its cell walls (Ookawa and Ishihara, 1993; Davì et al, 2019), plays an important role in lodging resistance in rice (Ookawa et al, 2010; Yano et al, 2015). Plant cell walls are mainly composed of cellulose, hemicellulose, pectin, lignin, and minor structural glycoproteins that form a crosslinked matrix.…”