Figure 8.

Light intensity increases repression and expression variability in strains carrying the dCas9-mCherry-LINuS and dCas9-mCherry-LINuS-Mxi1 repressors. (a) Strains carrying dCas9-mCherry-LINuS or dCas9-mCherry-LINuS-Mxi1 and the sgTEF1 guide RNA were exposed to increasing light intensities. Increasing light intensity increases repression in both the dCas9-mCherry-LINuS repressor and the dCas9-mCherry-LINuS-Mxi repressor, consistent with previous results. Error bars represent 95% confidence intervals on the average of the median fluorescence from n = 3 biological replicates. (b) Light intensity increases the population of low expressing cells while leaving a significant fraction of the population distributed through the wild-type (dark) expression levels. Dashed lines represent the first and third quartile for cells carrying dCas9-mCherry-LINuS/sgTEF1 in the dark. The most variable population is dCas9-mCherry-LINuS-Mxi1 at 100 µW/cm². This population has significant overlap with both the dark population as well as the constitutively repressed (dCas9/sgTEF1) population. Controls (dCas9 +sgTEF1, dark grey) and dCas9-Mxi1 +sgTEF1, light grey) are shown for comparison. (c) Plotting the subpopulation ratio (N_L/N_H) shows that increasing light intensity increases the ratio of low expressors to high expressors in the population (up to 10-fold for dCas9-mCherry-LINuS-Mxi1). The controls (dCas9, dCasi-Mx1) change the subpopulation ratio (N_L/N_R) 450- and 1500-fold respectively and are therefore not shown on this plot.