Modelling of Yeast Mating Reveals Robustness Strategies for Cell-Cell Interactions
Fig 9
Estimating the diffusion constant of a-factor.
(A) Projection lengths in bar1Δ versus Bar1+ a-cells. In the presence of Bar1, we only observed short-range matings in which both a-cells and α-cells possessed short projections. In the absence of Bar1 (bar1Δ matings), we observed longer projections made by the bar1Δ a-cells, whereas the α-cell projections remained short. The top two panels are fluorescent images of Spa2-GFP (a-cell) and Spa2-mCherry (α-cell) showing the adjacent/overlapping polarisomes indicating a successful mating. The bottom two panels are DIC images that depict the projection morphologies of the mating cells. Scale bars = 5 μm. (B) The relative projection lengths of α-cells versus a-cells in simulations compared to experiments. In the top bar graph, the α-cell projection length is presented as the fraction of the sum of the two projection lengths (n = 25 matings for Exp.); the average and standard deviation (error bars) are shown. The two-cell simulations with noise were performed as described in Fig 2 for varying α-factor diffusion values: Da = 0.1, 1, 10, and 100 μm2/s. The average and standard deviation of the normalized α-cell projection length from 10 simulations are shown. In the bottom bar graph, the corresponding unnormalized a-cell and α-cell projection lengths (mean ± SD in μm) are shown. The a-cells in both experiments and simulations are bar1Δ. (C) Concentration profiles of a-factor for different diffusion constants. The a-factor distribution is color-coded using gray scale at T = 830s in one example simulation for different diffusion rates. With a diffusion constant of 0.1 μm2/s, a-factor is highly localized to its source and does not reach the mating partner. With the diffusion constant of 100 μm2/s, a-factor spreads widely and is almost homogeneous distributed.