BB patterns are driven by dynamic remodeling of the apical cytoskeletons. (A) Model scheme. The cytoskeleton near the apical membrane (gray plane) is subject to contraction (gray arrows) by filament-bound motors and to diffusion and polymerization (top). BBs associated with the cytoskeleton through their BF are advected by cytoskeletal flows induced by filament reorganization (bottom). (B) Phase diagram showing the dependence of steady-state cytoskeletal patterns on κ_p and κ_c (left). The homogeneous state, spot pattern, and stripe pattern are represented by black, yellow, and red circles, respectively. Orange depicts a mixture of spots and stripes. Gray curve indicates the boundary separating the pattern-forming region $κ c >κ c *$ and spatially homogeneous state $κ c <κ c *$⁠. Small arrows represent fluid velocities (right). Green indicates a high concentration of cytoskeleton and white indicates a low concentration (right). Fluid viscosities are v₁ = 0.01 and v₂ = 0.03. (C) Pattern evolution of the model system with a high polymerization rate of κ_p = 3.5 and 133 BBs (circles). The BBs, which were initially in the floret pattern, sequentially presented the scatter, partial alignment, and alignment pattern: κ_c = 13, v₁ = 0.01, and v₂ = 0.03. T is the simulation time. (D) Changing the model parameters as follows: $κp: 3.5→0.5, ν1: 0.01→0.09, ν2: 0.03→0.27$ at the scatter pattern (T = 6) induced BB clustering. (E) A low polymerization rate κ_p = 0.1 did not result in any pattern formation. All parameters except for κ_p were the same as in C. See also Videos 9 and 10.