Figure 2.

Diversity of cyclin types influences interphase length, whereas amount of a single cyclin has little effect. (A) Schematic of the experiment. dsRNA to two of the three cyclins was introduced throughout the embryo in cycle 10. Rhodamine-tagged GST-CycB protein was then injected at one pole during interphase 13. Embryos were imaged in regions 1 and 2, and the timing of mitosis in the two regions was determined. (B and C) Video frames of cycle 13 in which the remaining cyclin is CycB (B) or CycA (C). After injection of the GST-CycB protein, red fluorescence is seen in the injected pole (rhodamine). The absence of red at the other pole shows that significant GST-CycB does not reach the other pole in this time frame. Noting time stamps (minutes and seconds) on the images, it can be seen that GST-CycB does not advance mitosis when introduced into the CycB alone embryo but does advance mitosis when introduced into the CycA alone embryo. Bar, 5 µm. (D) A compilation of timing results from these experiments. Error bars represent SDs. n = 3.