Fig. 6.

Optogenetically induced and spontaneous myotube contractions during development. (A-C′) Time points from spinning disc confocal movies of myotubes labeled by Mef2-GAL4, UAS-GFP-Gma and additionally expressing UAS-Channelrhodopsin at 46 h (A), 50 h (B) and 52 h (C) APF (Movie 10). Ca²⁺ influx and contractions are induced while imaging with 488 nm laser light. Bulges are marked by yellow arrows (A′,B′,C′) and myotube end movements with green and blue arrowheads. Note that myotube contractions increase at 50 h APF. (D) Quantification of myotube contractions; the number of contracting myotubes increases from 46 h to 50 h APF. Number of pupae: 8 at 46 h, 48 h and 50 h; 6 at 52 h. (E-G″) Time points from spinning disc confocal movies of myotubes labeled with Mef2-Gal4, UAS-Lifeact-Ruby and UAS-GCaMP6 imaged for a 20 min interval at 46 h (E-E″), 50 h (F-F″) and 52 h (G-G″) APF. Ca²⁺ influx is visualized in green and muscles in red (Movie 11). Bulges are marked by yellow arrows (E′,F′,G′) and myotube end movements with green and blue arrowheads. Note that myotube contractions increase at 50 h APF. (H) Number of myotubes that contract within 20 min intervals at 40 h, 46 h, 50 h and 52 h APF. Number of muscles: 38 at 40 h; 46 at 46 h; 31 at 50 h; 27 at 52 h. (I) Contraction frequency during development. Each point represents number of contractions of one myotube within a 20 min interval. The mean contraction frequency (blue line) increases with time. Scale bars: 50 µm.