Figure 4.

Measurement of Bcd degradation and correction for flux. (a) k_deg (X) in cycle 14 displayed for all degradation experiments with duration T = 8 min, comprising 60 embryos. t indicates the midpoint of the 8-min interval, in minutes after fertilization. (b) $Q_{df}\left(t_0+T\right)/Q_{df}\left(t_0\right)$ calculated for all experiments lasting T = 8 min. Labels 12–14 indicate the mitotic cycle number. The solid line represents the smoothing spline fit to all data smoothed by a Savitzky-Golay filter (26) of span 6. (c) Scaling of the surviving fraction according to waiting-interval duration T, measured early in interphase 14 (squares). Error bars indicate standard error. Least-squares fit (dashed line) has slope −0.028 min⁻¹, corresponding to the degradation rate shortly after the onset of interphase 14. Each data point bins all experiments with a given T whose midpoint falls between the dashed lines in a. (d) Measurement of fractional distribution of Dronpa-Bcd in cross sections of embryos in cycle 11 and earlier (blue), in cycles 12 and 13 (green), and in cycle 14 (red). $Q\left(r\right)/\Sigma Q$ indicates the fraction of total Dronpa-Bcd in an annulus of fixed width at distance r from the longitudinal axis of the embryo. The dashed line indicates the uniform distribution. A larger percentage of Dronpa-Bcd is located at the surface region of integration (yellow shading) in the later stages. (e) Degradation rate found by removing cell-cycle-periodic oscillations but with no correction for core-to-cortex flux (black), compared to the estimated k_deg obtained by assuming redistribution of Bcd as observed in cross sections (green) and that obtained by assuming Dronpa-Bcd redistribution identical to that of H2A-RFP (red). Shading indicates the standard error of this curve found by binning a moving window of 10 adjacent values.