Fig. 6. Aberrant centrosome behavior in pam-1. (A) Centrosome positions over time, measured from time-lapse images of embryos expressing ß-TUBULIN::GFP. Each point represents the average of six wild-type or seven pam-1 embryos beginning with the moment of the appearance of the centrosomes. In pam-1 embryos, centrosomes first became visible in the posterior of the embryo, but then quickly moved toward the center of the embryo. (B) A plot of centrosome position relative to the posterior pole from three wild-type and three pam-1 embryos over ten 20 second time points. Each horizontal series represents measurements from one embryo. Measurements were begun when the centrosomes first became visible. Stars indicate the position of the centrosomes when they first separated from one another. The centrosomes in pam-1 moved quickly toward the center of the embryo. (C, parts a-c) Images from a time-lapse ß-TUBULIN::GFP movie of a wild-type embryo show movement of the centrosomes over time. By 200 seconds, the centrosomes clearly flanked the sperm pronucleus near the posterior pole of the embryo. (C, parts d-f) In pam-1 the centrosomes moved quickly into the center of the embryo and remained close together before appearance of the pronuclei. (D, parts a-c) By DIC optics, the centrosomes appeared as small dots flanking the pronuclei until the first spindle assembled (white arrowheads). (D, part d) By contrast, in some pam-1 embryos, the centrosomes began to nucleate microtubules before pronuclear appearance and were visible by DIC optics (white arrowheads). (D, parts e-f) In most cases, the centrosomes reduced in size as the pronuclei formed and then grew larger again as the mitotic spindle assembled. Scale bar: 10 µm.