Fig. 2. Live imaging of migration and fusions of NCDs at the endosperm posterior pole. (A) Confocal sections selected from a time-lapse series of 67 images acquired every 10 minutes. The whole video can be seen at http://dev.biologists.org/supplemental/. The endosperm endoplasmic reticulum is labelled with mGFP5 expressed under the control of the specific enhancer KS22 (Boisnard-Lorig et al., 2001). Hence each NCD is labelled individually and the cyst (c) appears as a large fluorescent mass at the posterior pole. The seventh mitotic division has taken place 40 minutes before time 0 minute. After mitosis, NCDs migrate toward the cyst (170 minutes). Later, a NCD migrates towards a neighbouring NCDs closer to the posterior pole and eventually fuses with it (370-430 minutes). The resulting nodule attracts a third NCD while other NCDs migrate and fuse (590-660 minutes). (B) A time-lapse series similar to the one shown in A, selected from 82 images acquired every 10 minutes, showing the absence of oriented migration and non-specific fusions of NCDs in the mutant fis2-3 background. The seed was selected as fis2-3 at the mid-globular stage on the basis of its strong fluorescence, persistent in all domains of the endosperm, provided by the activity of the enhancer KS117 that drives expression of mGFP5 (Sørensen et al., 2001). A mitotic division has taken place 20 minutes before time 0 minute and no posterior migration of NCDs is observed in comparison to WT. No specific migration nor oriented fusion is observed later in development and unusually large nodules assemble as a result of `passive' engulfing by growing cytoplasm (360-510 minutes). Gradually, the polarised anteroposterior arrangement of NCDs, nodules and cyst is lost (810 minutes). Scale bars: 20 µm (all sections).