Dynamics of SIN Asymmetry Establishment
Figure 6
Simulations of the most peculiar observations in SIN asymmetry establishment.
(A) We simulated the laser ablation of the new SPB after anaphase (top), what leads to SIN activation at the old SPB [42]. At 200 time steps (horizontal dotted line) we stopped transport towards the new SPB and let all its content diffuse into the cytoplasm. (B) Simulation of the termination of SIN activity. At 200 time steps we induced the production (or reduced degradation) of new Byr4 molecules (as a proxy for the unknown signal that turns off SIN). At the same time we cut the communication between the two SPBs as it happens at the end of cytokinesis (“separated”, lighter color curves) or let the two SPBs communicate through the cytoplasm as it happens in some dikarions [43] (Non-separated, darker color lines and dots on top panel). If the cells are separated the newly formed Byr4 goes to the only existing new SPB, while if the cells did not separate it will be constantly recruited to the old SPB, thus SIN at the new SPB will turn off much later. (C) Seesaw metaphors of the two cases of panel B (seesaws are common examples of antagonistic interactions with two opposing steady states). The right arm of the seesaws represent SIN activity at the two SPBs, and they are connected to each other (water can flow between them in the metaphor - molecules can diffuse between SPBs in cells). The situation where the active and inactive SPBs are separated is captured on the left, where both SPBs are active, water is poured in (signals induce SIN inactivation) they both can turn together. On the right (non-separated active and inactive SPB) one SPB has high SIN, the other has low SIN. When water is poured in, first it flows to the lower (already inactive SIN) bucket and the upper seesaw will turn only if the lower bucket and the pipe are full.