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. 2017 Jun 28;4(6):622–635.e9. doi: 10.1016/j.cels.2017.05.010

Figure 2.

Figure 2

Cellular Variation of FLC mRNA Production and Degradation in Outer Layer Root Cells

(A) Schematic of FLC gene with exons (boxes) and introns (dashed lines) indicated, and different probe sets for labeling FLC mRNA (green) and FLC full-length intron 1 (red). Fluorescence localization (z-stack projection) of FLC mRNA, full-length intron 1, and an overlay containing mRNA, intron 1 FLC, and DAPI stain (blue) in representative ColFRI outer layer root cells. Scale bar, 5 μm.

(B) Cellular FLC intron 1 foci counts (gray, n = 106 cells from four biological replicates, i.e., roots from different plants).

(C) Histogram of cellular mRNA foci counts (blue, n = 209 cells from eight biological replicates) and a Poisson distribution fit (red), which would be expected from a simple birth/death process of FLC mRNA production/degradation with constant probabilities per unit time (see schematic above).

(D) Cellular FLC intron 1 foci counts after treatment with ActD or DMSO (mock) for 4 hr and 6 hr. With ActD, after 4 hr and 6 hr the vast majority of intron 1 signal has disappeared. Mock-treated FLC mRNA distributions are shown in Figure S1B.

(E) Left panel: histogram of cellular FLC mRNA foci counts after 4 hr of ActD treatment (blue) and Poisson decay process prediction (red). Right panel: cumulative distribution functions (CDFs) of the FLC mRNA foci counts and Poisson decay process prediction. Schematic above histogram shows FLC mRNA degradation only, as appropriate for ActD treatment.

(F) As in (E) but after 6 hr of ActD treatment. Cells in (D), (E), and (F) are pooled from three biological replicates for each treatment and time point.

(G) Scatterplot of cellular FLC mRNA foci counts (same data as in C; blue) as a function of cell volume, together with least-squares fit (red). Schematic above shows FLC mRNA production increasing with cell volume and volume-independent degradation.

(H) Variance plotted against mean of cellular FLC mRNA foci counts, both for given binned cell volume (ColFRI, Volume-binned). Also shown is the behavior predicted by model with Poisson probability distribution with parameter βV(Poisson), as well as a Poisson model that takes into account volume measurement error (Poisson + Volume error). All error bars indicate standard errors on the respective quantities.