Pheromone-dependent cell cycle dynamics. (A) Schematic of MPF repression dependent on the extracellular amount of pheromone molecules. M-factor molecules (red circles) have an effect on cells of mating P, while P-factor (blue diamonds) only influences the intracellular dynamics of M-type cells. P-factor pheromone is catalytically degraded by Sxa2 which is secreted by cells of mating type M only. (B) MPF trajectories and cell cycle phases of a simulation run without pheromones. Mass-doubling time T
= 232 min. (C) An extracellular pheromone amount of 200 molecules reveals no significant difference of MPF and cell cycle dynamics. (D) Large pheromone amount (600 molecules) leads to MPF repression and subsequent adaptation due to increasing cell size. Cell cycle length is significantly increased due to an arrest in the G1 phase of the cell cycle.