Morphoelasticity in the development of brown alga Ectocarpus siliculosus : from cell rounding to branching

Abstract

A biomechanical model is proposed for the growth of the brown alga Ectocarpus siliculosus. Featuring ramified uniseriate filaments, this alga has two modes of growth: apical growth and intercalary growth with branching. Apical growth occurs upon the mitosis of a young cell at one extremity and leads to a new tip cell followed by a cylindrical cell, whereas branching mainly occurs when a cylindrical cell becomes rounded and swells, forming a spherical cell. Given the continuous interplay between cell growth and swelling, a poroelastic model combining osmotic pressure and volumetric growth is considered for the whole cell, cytoplasm and cell wall. The model recovers the morphogenetic transformations of mature cells: transformation of a cylindrical shape into spherical shape with a volumetric increase, and then lateral branching. Our simulations show that the poro-elastic model, including the Mooney–Rivlin approach for hyper-elastic materials, can correctly reproduce the observations. In particular, branching appears to be a plasticity effect due to the high level of tension created after the increase in volume of mature cells.

Physics of growing biological tissues: the complex cross-talk between cell activity, growth and resistance

“…For instance, plants are appropriately described as elastic solids, consistent with the solid wall of plant cells and limited remodelling [55,56]. This is also true for algae, although their cell walls are softer than the plant ones [57,58]. For tumour models, the situation is less clear, since tumour multicellular spheroids have been shown to be characterized by a surface tension reminiscent of a liquid at long times [59], while real tumours, whose microstructures are reinforced with stiff ECM [60,61] or pathological fibrosis are well described on elasticity basis [62].…”

Determination of the Structural Characteristics of Microalgal Cells Walls under the Influence of Turbulent Mixing Energy in Open Raceway Ponds

“…These properties could not be measured because the present study did not cultivate the microalgae (Chlorella cells). Therefore, the needed Chlorella cell properties were obtained from past experimental studies by Munns et al [22], Williams and Laurens [31], Wijaya et al [32], and Jia et al [33]. The physical, fluid, and structural properties of the spherical microalgal cells (Chlorella) are presented in Table 1 [22,[31][32][33].…”

“…The structural properties of the microalgal cell wall used in this study are presented in Table 1 [22,32,33].…”

“…Therefore, the needed Chlorella cell properties were obtained from past experimental studies by Munns et al [22], Williams and Laurens [31], Wijaya et al [32], and Jia et al [33]. The physical, fluid, and structural properties of the spherical microalgal cells (Chlorella) are presented in Table 1 [22,[31][32][33]. From a fluid dynamics point of view, four edges (leading, trailing, top, and bottom) of the microalgal cells were defined with respect to flow direction for improved understanding of microalgal cell damage in the raceway pond ( Figure 1a).…”

“…Therefore, the cell wall of a spherical microalgal cell (Chlorella) was modeled as an elastic structure filled with cytoplasm [33,38]. The governing equation to compute the solid displacement for the microalgal cell wall is as follows:…”