Nuclear Bcd concentration dynamics.
A Typical nuclear (blue) and cytoplasmic (green) Bcd-GFP concentration development during nuclear cycle 13. Three intervals correspond to: I) Nuclear envelope breakdown and diffusive nuclear Bcd-GFP release, II) rapid refilling of newly formed nuclei after mitosis, and III) interphase 13.
B Fluorescence recovery after photobleaching of a single nucleus of a Bcd-GFP embryo during interval III of nuclear cycle 14. Blue curves are the recovery curves of a 4 times successively bleached nucleus, red curve is the concentration in a neighboring unbleached nucleus. Bleach pulses (10 – 15 s long) are indicated by gray arrows. Data points are in 4 s intervals. The time constants
τ of exponential recovery fits are 60 s, 53 s, 52 s, 50 s, respectively for the 4 bleaching traces. The linear decay of the red curve is due to the increasing nuclear diameter during interphase which leads to an effective decrease in the nuclear Bcd-GFP concentration (see text).
C Development of nuclear diameter from nuclear cycle 10 to 14. Blue and red data points correspond to two different embryos (blue corresponds to the data set of ). The nuclear diameters at the end of interphase (averaged over 2 embryos) in nuclear cycles 10 to 14 are 10.0
μm, 10.5
μm, 9.2
μm, 8.2
μm, 6.5
μm, respectively.
D Relative intensity (blue), relative number of molecules (green) and ratio of number of molecules to influx (red) as a function of time during nuclear cycle 13. Blue curve corresponds to average nuclear intensity
I(
t) represented by the blue trace in during interphase 13. Green curve corresponds to the product of

where 2
rn(
t) is the nuclear diameter represented by the blue trace in C. Red curve corresponds to the product

. The right side of the vertical axis has been normalized to yield the cytoplasmic diffusion constant

, see text. To quantify the observation that

is constant while

, we looked for linear correlations between these quantities and time; for

the correlation (0.50) is highly significant (
p = 0.0013), while for

there is essentially no correlation (0.01,
p = 0.93) – data sets for five embryos showed similar results.