Figure 3. The slow pathway specializes in matching Hog1 dynamics to volume recovery by being most sensitive to the network’s integral feedback.

(A) Before reaching Hog1, the signals from each pathway are transduced through Pbs2, and we perturb the HOG network by controlling PBS2 expression through a TET inducible promoter. Reduced induction of PBS2 compromises the network and decreases the maximum activity of Hog1. This reduction in activity should be compensated by the system’s integral feedback lengthening the nuclear residence of Hog1 (box inset). (B) Measuring relative to unperturbed Pbs2, under-expression of Pbs2 reduces the amplitude of mean Hog1 nuclear localization, but increases its adaptation time on average in wild-type cells (1 M step; arrows indicate time for 85% adaptation). (C,D) Mean Hog1 dynamics for the slow and fast mutants show that only the slow mutant extends the adaptation time of Hog1 like the WT. Insets: Mean ratio for three experiments of the adaptation time of Hog1 to the adaptation time of the volume in single cells. Error bars are SEM.

DOI: http://dx.doi.org/10.7554/eLife.21415.008

Figure 3—figure supplement 1. Only the wild-type and slow mutant can compensate when Pbs2 levels are reduced by increasing the adaptation time of Hog1.

(A) Average volume as a function of time in the three strains for different levels of Pbs2 repression. The time to recover the volume is extended in all strains for reduced levels of Pbs2. (B) Distributions of the ratio between the adaptation time of Hog1 and the adaptation time of the volume in single cells for different levels of Pbs2. Each distribution comprises at least 200 cells from three independent experiments (27 experiments in total). The median is indicated by a coloured line on the x-axis. For the fast mutant, reduced levels of Pbs2 result in premature adaptation of Hog1 relative to the volume recovery (p<10⁻⁶: two-sided Wilcoxon rank sum test for equal medians and indicated by asterisks). For wild-type and the slow mutant, the ratio of the time of adaptation of Hog1 adaptation to the time of adaptation of the volume is not significantly affected by reduced Pbs2 levels (p>0.1). (C) The correlation between adaptation time of Hog1 and the time for volume recovery as a percentage of volume recovery calculated by pooling together the data from B (cf. Figure 2C).

DOI: http://dx.doi.org/10.7554/eLife.21415.009