The development of Drosophila embryos visualized with a Polycomb-GFP fusionprotein

If you are not coming from there anyway, please go the Poycomb - GFP introduction page  and the embryo development introduction page first.

In all movies the embryo is viewed laterally, the ventral side left  and anterior towards the top of the image. Image size is 0.5 mm from top to bottom. The stack of four (or five) confocal sections shown in each frame was recorded at one time point (that is, of course, consecutively, one section after the other, starting with the one at the bottom. The scanning of one image stack took 55 seconds). The bottom section is relatively close to the center of the embryo, the top section is grazing through the outer edge of the embryo.

The first two movies show the embryo from the blastula stage until hatching of the larvae which can be observed at the end of these movies. The hatching of the larva at the end of the movie demonstrates that the observation conditions, e.g. phototoxicity, were not lethal. The waiting time between the recording of two stacks  is 15 minutes in these movies (excluding scanning time). The first movie contains 126 frames, the total duration is thus about 33 hours, the second movie has 130 frames, thus spanning about 34 hours. During the later stages of embryonic development the embryo starts to move within the egg. Since it took about 14 seconds to record one image (frame averaged), the images are somewhat blurred due to that motion . The movement of the larvae also caused the rotation of the egg towards the end of movie 1.

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The third movie focuses on early stages. It starts before blastoderm and ends after germband retraction. Recording conditions were as above except that there was a variable waiting time between stacks: 5 minutes between the first 121 stacks, thereafter 30 minutes (each including 55 seconds scanning time). The larger intervals start at the beginning of germband retraction. The 140 frames thus add up to 120x5 +19x30 min = 19 hours 30 minutes. Nuclei become visible when they get to the surface of the embryo to form the blastoderm (10th frame of the movie). Cycle 14 can be easily distinguished from earlier cycles by the longer duration and the lack of mitotic waves thereafter. Then one can count backwards through the mitotic waves to determine when the nuclei reached the surface: It is during cycle 10 (in agreement with the literature).

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The fourth movie starts before blastoderm and stops somewhat after pole cell movement begins. Delay between frames is 6 minutes (including scanning) and 34 frames are shown, adding up to 3 hours 18 minutes. As in movie 3, the nuclei are visible first during cycle 10.

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