Back to article: Antagonism between salicylate and the cAMP signal controls yeast cell survival and growth recovery from quiescence

FIGURE 3: Specificity and efficacy of PKA suppressive activity. (A) Dominant cAMP effect in suppressing the SA-induced delay of cell growth recovery. cyr1Dpde2Dmsn2Dmsn4D long-term quiescent cell populations were supplied (red) or not (black) with 3 mM cAMP or with 3 mM salicylate plus (pink) or minus (blue) 3 mM cAMP when inoculated into fresh medium, monitoring growth by measuring OD at 600nm. The Log10 values of the experimental points were plotted against time (hours) and fitted with linear regression curves. The variations of the time in which growth is reactivated in the different conditions are estimated as explained in the previous figure legend. 3 mM salicylate caused a delay in growth recovery of ~2.13 hours compared to the untreated control (represented by a right pointing arrow) whereas the culture experiencing both cAMP and salicylate could start the growing phase ~3.6 hour earlier than that with the drug alone(left pointing arrow). Noteworthy, its growth curve overlapped that of cells treated only with cAMP. (B) Specificity of cAMP effects for the reactivation but not the rate of cell growth. cyr1Dpde2Dmsn2Dmsn4D mutant cells were treated with 6 mM salicylate and supplied (red) or not (black) with 3 mM cAMP as described in previous figure. The Log10 of OD600nm values taken during the time course experiment were fitted with linear regression curves. At this dosage the drug increased the log-phase generation time from ~2 to 2.61 hours irrespective of the cAMP presence. However, the addition of cAMP still shifted much earlier, namely ~5.22 hours (left pointing arrow), the growth recovery of the culture. (The figure is representative of the results of 5 independent experiments). Inset. The regression curves of the above graph are drawn (line colours as in the main graph) together with that of a mutant cell culture supplied with cAMP only (lilac line). The coordinates of the crossing point (arrow) between the two cultures with cAMP are indicated. In particular, the “6 mM SA+cAMP” and “cAMP only” curves converged at about the cell density of inoculums, namely OD600@0.005, and at a time of ~8.6 hours (as determined with a graphing software; see Materials and Methods). Note that the moment of inoculation is put here as time zero.

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