ABSTRACT
From bacteria to humans, individual cells within isogenic populations can show significant variation in stress tolerance, but the nature of this heterogeneity is not clear. We used single-cell RNA sequencing to quantify transcript heterogeneity in single S. cerevisiae cells treated with and without salt stress, to explore population variation and identify cellular covariates that influence the stress-responsive transcriptome. We leveraged the extensive knowledge of yeast transcriptional regulation to infer activation of upstream regulators in individual cells. We tested resulting hypotheses with live- and single-cell fluorescence microscopy, focusing on pairs of differentially labeled factors, including Msn2 with Hog1, Dot6 or Sfp1, expressed in the same cells. Our results revealed surprising cases of regulator decoupling for pathways thought to be coregulated based on bulk populations. The impact of cell cycle and metabolic fluctuations on the stress response are also discussed.
