Figure 1. Nucleoli in the eye–antennal imaginal disc.

A. Epithelial layer of the eye-antennal imaginal disc. Nucleoli labeled in magenta (anti-fibrillarin); mitotic figures labelled in green (anti-phosphoH3). Postmitotic fate specification begins within the morphogenetic furrow (yellow arrow), flanked by a First Mitotic Wave where unpatterned proliferation ends (orange arrow), and the Second Mitotic Wave where a subset of retinal progenitor cells divide (blue arrow). Blue bar indicates the approximate extent of Hedgehog (Hh) expression posterior to the furrow. Hedgehog induces Dpp within the furrow (lavender bar). Dpp and Hh together regulate differentiation and the cell cycle arrest that precedes the furrow (see text). B. Peripodial layer of the eye-antennal imaginal disc. Proliferation is largely unpatterned. C. Higher magnification of antennal region (box ‘c’ in panel A). Nucleoli were smaller in the cells of more distal regions (towards the top). D. Higher magnification of anterior eye region (box ‘d’ in panel A). Nucleoli resemble those from the antennal disc. E. Higher magnification of posterior eye region (box ‘e’ in panel A). Nucleoli are much smaller than in the antennal disc or anterior eye disc. Labeling intensity is also reduced (peak labeling is approx 0.6x the gray value of panel F). F. Higher magnification of the peripodial epithelium. Nucleoli are similar in size to the anterior eye disc and the antennal disc, but larger and more intense than nucleoli from the posterior eye region (compare panel E).