C,D,E Examples of embryos expressing the tFT-Bcd reporter with C: mCherry-sfGFP-Bcd, D: fmCherry-sfGFP-Bcd, and E: mCherry-sfGFP. For all, (i) Images of "shells" of embryos in early n.c. 14. 3D images of the embryos were generated, and then the interior of the embryo was erased, leaving only the embryo cortex to improve clarity (ii) Mean AP intensity profile of each color for the embryo in i. Shade region represents ±1 s.d. Inset shows same profiles after multiplication of red intensity by constant factor. Data binned into 10 µm bins (n=4 embryos). (iii) Ratio of green over red signal, reflecting protein age. The thin lines represent individual embryos, while the thick solid line is the mean. The solid dashed line depicts the mean green/red ratio for a line with the tFT-Bcd reporter but lacking endogenous Bcd (BcdE1 mutant, n=4). 