Tubule-to-sheet conversion of the ER in a fractionated system. An ER network was formed by incubating interphase cytosol, light membranes, and an energy regenerating system at room temperature for 20 min. Cyclin BΔ90 and the fluorescent hydrophobic dye octadecyl rhodamine were added, and the changes of ER morphology (in white) were followed over time. Time-lapsed images were acquired with a spinning-disk confocal microscope at 2-s intervals for 2 min. The video is shown at five frames per second. Arrowheads point to sheet-like structures that appear in tubules. Arrowheads of the same color point to sheets that eventually merge. Still images of this video were used for Fig. S3 D. Bar, 10 µm.
