Plk4 concentration modulates the onset of centrosome biogenesis. (A) Inter-event distance at low Plk4 concentration. Cumulative distribution of observed (obs) and simulated (sim) inter-event distances measured in 3D for the first four centrosomes formed de novo in the explants, at the lowest Plk4 overexpression (0.16 relative concentration of Plk4). The gray envelope indicates the 95% confidence interval (from quantile 0.025 to 0.975) for the simulated data. (B) Plk4 titrations were performed by mixing WT and Plk4 overexpressing eggs at different ratios. Time of onset of de novo centriole biogenesis is shown as cumulative distribution function for four relative concentrations of Plk4. Lower concentrations delay the initiation of de novo centriole biogenesis, with a large majority of the individual explants not forming centrioles, at lower concentrations, during the observation time. (C) Time to the first de novo event, and inter-event time between the first and second de novo events in mixed explants with different concentrations of Plk4. In all dilutions tested, the time for the first event to occur is longer, while the first to second inter-event time is unaffected. Median with interquartile range is presented for n = 56, n = 62, n = 39, and n = 25 explants at 1, 0.5, 0.33, and 0.16 relative concentration of Plk4, respectively. (D) The duplication time of the first centriole formed de novo is similar at high (1) and low Plk4 concentration (0.16). Centrioles formed de novo duplicate, on average, 3 min after their biogenesis, at both high (1, n = 44 centrioles) and the lowest (0.16 Plk4 dilution, n = 20 centrioles) concentrations of Plk4 investigated. The horizontal lines and error bars represent the respective median and interquartile distance. The duplication time is not statistically different between the two conditions (Mann–Whitney test, P = 0.59).