Centrosome separation initiation is delayed in KLP-7 depleted embryos. (A) Average residency time of microtubules at the cortex of AB and P1 in control and KLP-7–depleted embryos. Plus end microtubules were visualized using a strain expressing EBP2::GFP (TH66). In control, 1,303 tracks were measured in five AB cells and 770 tracks in five P1 cells; in KLP-7–depleted embryos, 1,786 tracks were measured in six AB cells and 1,372 tracks in five P1 cells. Each value corresponds to the mean residency time at the cortex in seconds ± SEM. (B) Quantification of cortical microtubule density. Tracking of microtubules was performed using a macro developed in ImageJ (see Materials and methods). Each value corresponds to the mean number of microtubules at the cortex in a surface of 100 μm2 (n = 5 cells each). (C) Quantification of microtubule polymerization rate. The polymerization rate was based on EBP2 comets growing out from the centrosomes toward the cortex for at least 10 frames. A total of 110 microtubules were counted in WT AB cells, 90 in P1 cells, 120 in klp-7(RNAi) AB cells, and 111 in klp-7(RNAi) P1 cells (at least five cells each). (D) Tracking of the centrosome-to-centrosome distance over time in control embryos (n = 9 AB cells and 9 P1 cells) and in klp-7(tm2143) embryos (n = 17 AB cells and 15 P1 cells). T = 0 was set at NEBD for AB and P1, respectively. The green line indicates the minimal distance, under which it was not possible anymore to resolve the two centrosomes. Error bars represent SEM. The statistical test used is indicated in Table S1. *, P ≤ 0.05; ****, P ≤ 0.001.
