Figure 4.

Counterintuitive predictions arising from asymmetric division errors and consequences of length or volume sensing. (A) Possible explanation of how an increase in the asymmetry error at division brings the birth-division slope closer to zero. Black bars indicate the width of the distribution of the division length. (B) Size homeostasis plot for pom1Δ (FC2063, n = 1757, data from (1)). Slopes of reported fit lines are +0.15 ± 0.03 for the sizer regime (light blue color, length at birth less than 7 μm) and +0.86 ± 0.03 for the adder/timer-like regime (gray color, length at birth greater than 7 μm). In the sizer regime, division length has a CV of 9.0%, higher than the WT, but a lower birth-division slope (+0.15 vs. +0.25 for the WT as reported in Fig. 1A), as predicted by the model. (C) Size homeostasis data for the cdr2-T166A rga2Δ mutant that implements length sensing show near-perfect sizer behavior (FC3218, n = 1785, data from (1)). (D) Size homeostasis data for the cdr2Δ mutant, which implements volume sensing. Regression line and reported slope of +0.47 ± 0.04 refer to the binned data with length at birth smaller than 10 μm (green color). Cells with length at birth greater than 10 μm (gray color) show a slope of +0.88 ± 0.16 (FC3161, n = 1046). Binned data (with mean value ± standard error) shown as bold circles in (B)–(D). (E) Summary of the agreement between experimental slopes and values obtained by the model. Data points show the mean value ± standard error (see also Fig. S6B).