Jia F, Ben Amar M, Billoud, B, Charrier B. 2017.
siliculosus: from cell rounding to branching.
J. R. Soc. Interface 14: 20160596.
In brief: A biophysical model based on the poro-elastic properties of the cells of the filamentous brown alga Ectocarpus is described, which allows to simulate cell shape changes and subsequent filament branching during the algal growth. This shows that mechanical factors only can account for the major developmental processes as observed in vivo in this organism.
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.