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. 2024 Apr 3;12:RP88750. doi: 10.7554/eLife.88750

Figure 5. HOG pathway mutants exhibit a lower death rate and an increased population growth rate under in-phase stresses (IPS).

(a, b) Images of wild-type (a) and pbs2Δ mutant (b) cells before (t=0 min) and after (t=600 min) growth in IPS (left) and alternating stress (AS) (right) conditions. Fluorescence and bright-field images were merged to visualize nuclei marked with HTB2-mCherry. White arrows indicate nuclei of representative dead cells. Scale bars represent 10 µm. (c, d) Death rates (c) and population growth rates (d) of the reference strain and seven deletion mutants under IPS and AS conditions. Population growth rates were calculated as the difference between division rates (Figure 4b) and death rates (c). Bars show mean rates measured in different growth chambers. Error bars are 95% confidence intervals of the mean. Red symbols show the average rate for each field of view. Results of t-tests comparing the wild-type and mutant strains under the same conditions are indicated above each bar; results comparing the same strain under different conditions are shown above each pair of bars (ns p>0.05; *0.01<p<0.05; **0.001<p<0.01; ***p<0.001). The initial number of cells analyzed among replicates ranged from 97 to 467 in (c, d). (a–d) Cells were grown under fluctuations of 2% glucose and 1 M sorbitol at a period of 24 min.

Figure 5—source data 1. Source data for Figure 5.

Figure 5.

Figure 5—figure supplement 1. Dynamics of cell death and population growth rates under combined stresses and alternating stresses (AS).

Figure 5—figure supplement 1.

(a) Death rates and (b) population growth rates (calculated as the difference between the division rate and death rate) in in-phase stress (IPS) (dark gray) and AS (light gray) conditions with a period of 96 min and 2% glucose. (a, b) Bars show the mean values measured among different growth chambers sharing the same environmental condition. Error bars are 95% confidence intervals of the mean. Red symbols show the average death rate or population growth rate for each growth chamber. Results of t-tests comparing the wild-type and mutant strains under the same conditions are indicated above each bar; results comparing the same strain under different conditions are shown above each pair of bars (ns, p>0.05; **0.001<p<0.01; ***p<0.001). (c, d) Temporal dynamics of death rate averaged across all 96 min periods of growth in (c) IPS and (d) AS conditions for wild-type (black) and pbs2Δ mutant (green) cells. Each dot shows the death rate during a window of 6 min centered on that dot and averaged across all fields of view sharing the same conditions and among all periods in the experiment (average of 18 to 30 measurements per dot). Gray and green areas are 95% confidence intervals of the mean division rate. Horizontal dotted lines show the mean death rate among all data collected in each half-period (i.e. in each medium since the medium is changed at the start and the middle of each period [vertical dotted line]). Colored graphs are used to represent the periodic fluctuations of glucose (orange) and/or sorbitol (blue) in the medium; hatching represents stress. (e, f) Average death rates measured at six intervals of time in IPS (dark gray) and AS (light gray) conditions at a period of (e) 24 min or (f) 96 min. Bars show the mean death rate measured in different growth chambers sharing the same conditions. Error bars are 95% confidence intervals of the mean. Red symbols show the average death rate for each field of view and time interval.
Figure 5—figure supplement 1—source data 1. Source data for Figure 5—figure supplement 1.
Figure 5—figure supplement 2. Death rates of wild-type and sic1 mutant cells under periodic fluctuations of hyperosmotic stress with or without fluctuations of glucose availability.

Figure 5—figure supplement 2.

(a) Death rates in constant 2% glucose with repeated addition and removal of 1 M sorbitol at a period of 24 min. (b) Death rates in in-phase stress (IPS) (dark gray) and alternating stress (AS) (light gray) conditions with a period of 24 min and 2% glucose. (a, b) Bars show the mean death rates measured among different growth chambers sharing the same environmental condition. Error bars are 95% confidence intervals of the mean. Red symbols show the average death rate for each growth chamber. Results of t-tests comparing the wild-type and mutant strains under the same conditions are indicated above bars (ns, p>0.05; *0.01<p<0.05; **0.001<p<0.01; ***p<0.001). The initial number of cells analyzed among replicates ranged from 14 to 120.
Figure 5—figure supplement 2—source data 1. Source data for Figure 5—figure supplement 2.