Figure 4.

Proper SAC silencing requires biphasic scaling law between spindle size and cell size. (A) Phase diagram of SAC silencing behavior given cell size and spindle length. The aspect ratio is fixed at 0.8. The experimental data (colored dots) are adapted from Crowder et al. (5). (B and C) Final signal at the spindle pole as function of cell size and spindle size. The spindle size is normalized against cell size to demonstrate relative size. The final signal is expressed in relative level to the threshold value. A critical cell size exists upon which the dependence of the spindle pole signal on spindle size switches direction. (D) Major processes that determine the spindle pole signal, along with estimated timescales for each process in small and large cells (Table S1). (E–H) Dependence of critical cell size on various model parameters. In (D–H), D ∼ diffusion coefficient of streaming proteins; V ∼ convection speed of streaming proteins; Δ ∼ cell diameter; L ∼ spindle length; and δ ∼ diameter of spindle pole (compare to Fig. 1A). Red circles: nominal parameter values (Table S1).