[MS15] Toward creation of mathematical models by which treasures can be found in developmental biology

[MS15-04] Mechano-geometric control of stem cell divisions mediates plant body symmetry diversity in 3D computational model

*Naoya Kamamoto¹, Koichi Fujimoto¹ (1. Hiroshima university (Japan))

Keywords:

cell division,symmetry,stem cell,plants,mechanics

Cell division orientation plays a major role in the plant body plans. Plant cell division orientation is determined by cell geometry and mechanics. The default geometric (Errera’s) rule controls the orientation ubiquitously from algae to angiosperms, while the mechanical (maximal tension) rule prevails under mechanical stress in Arabidopsis. However, whether and how the two rules regulate the diverse body symmetry of land plants remains unclear. In bryophytes and ferns, a single apical stem cell (AC) on their growing tip is mostly tetrahedral shaped where differentiated daughters are periodically cut off and divided in a parallel (leafy liverworts and ferns) or slightly inclined manner (mosses) to 3-cutting faces, clade-specifically producing 3-fold or spiral body symmetry. Additionally,,,,,4-fold or 2-fold body symmetry are produced by wedge-shaped AC in Lycophytes and thalloid liverworts, respectively. Here we show by 3D computational model simulations that the geometrical/mechanical control of division orientation thoroughly reproduces diversity of AC shape and body symmetries. Tetrahedral AC and 3-fold symmetry are recursively maintained, accounting for leafy liverworts and ferns, under the geometric rule alone and resultant geometric similarity. Importantly, spiral body symmetry, typical of mosses, and 4-fold symmetry with wedge-shaped AC, typical of thallus liverworts and Selaginella rhizophore, emerged specifically under the maximal tension rule depending on cell wall stiffness. These results suggest that the geometrical and mechanical control of AC division planes and the regulators are core to diversifying land plant symmetry.