Evolution of the fluorescence level and variation in sub-clones.

<p>A. Evolution of the median YFP fluorescence level in populations derived from high- (blue line), low- (green line) and non-fluorescent (red line) founder cells. The time scale is in days after the sorting of founder cells. Note that after more than 20 days it is still possible to recognize which type of founder cell the population derived from. B. The Normalized variance (NV) of the populations originated from high- or low-fluorescent founder cells vary little over time (presented on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115574#pone-0115574-g002" target="_blank">Fig. 2A</a>). The initially high NV in populations derived from non-fluorescent cells is the consequence of the re-expression of the YFP fluorescence in a small fraction of cells. C. The fraction of the expressing cells in the populations derived from non-fluorescent, low- or high-expressing founders. The varying proportion of expressing cells in the populations derived from non-expressing founders suggests re-expression of the reporter gene is not uniform in these clones. The populations originated from low-expressing founders contain varying proportions of cells that have silenced the reporter gene, while silencing is less frequent in the populations derived from high-expressing founders. D. The expression/silencing of the CFP-coding reporter gene is independent of the YFP-coding reporter gene as indicated by the varying fractions of CFP-expressing cells in the same subclones presented on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115574#pone-0115574-g002" target="_blank">Fig. 2A</a> to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115574#pone-0115574-g002" target="_blank">Fig. 2C</a>. All but one YFP negative cells were positive for CFP (left) on the day of cloning, one low YFP-expressing (middle) and four high YFP-expressing (right) clones derived from cells that did not express CFP.