Figure 6

Optogenetic activation of a small number of smooth muscle cells, neurons or endodermal cells could induce or arrest gut movement. (a–g) Activation of circular smooth muscles caused local contraction of the gut. Blue-light irradiation (indicated by a circle) of circular muscles expressing ChR2-eYFP in SAGFF(LF)134A; Tg(UAS: ChR2-eYFP) (a,b) and the control expressing GFP in SAGFF(LF)134A; Tg(UAS: GFP) (d,e) in the posterior gut at 8 dpf. The changes in the width of the gut (c,f). Green lines indicate the position of the measurement in the spot of blue light; red lines at the oral side of the spot; yellowgreen lines at the anal side. Blue lines in (c,f) indicate the periods when blue light was applied. Schematic representation of the gut movement induced by the spot light (g). Lateral views. Ant., anterior. Scale bars, 50 μm. Also see Supplementary videos ³ and 4. (h–k) Activation of a single neuron could induce contraction at the oral side of the neuron. Live view of the midgut (h) and the neuron expressing ChR2-eYFP in a spot of the blue light, extending one of the neurites anteriorly (i) and two kymographs of (g) at the oral-to-anal (green) and the dorsal-to-ventral (red) dashed lines (j). Schematic representation of the gut movement induced by the spot light (k). Scale bars, 50 μm for h and 10 μm for i. Also see Supplementary video 5. (l–q) Activation of two neurons located near the anus could cause the arrest of the local gut movement at 8 dpf of Tg(hsp70: Gal4); Tg(UAS: ChR2-eYFP). Live image of the gut (l). Ant., anterior. Double immunostaining for anti-GFP indicating the cells expressing ChR2-eYFP (green) and anti-5-HT (magenta) (m). Enlarged views of these neurons at lateral view (n) and dorsal view (o) indicating that some axons are extending across the dorsal midline of the gut. Dotted line indicates the dorsal midline. Kymograph at the dashed red line in (l). Schematic representation of the arrest of the gut movement induced by the spot of blue light (q). Scale bars, 20 μm. Also see Supplementary video 6. (r–u) Activation of cells in the endodermal cell layer could induce a peristaltic reflex-like movement (a local constriction of the gut and active movement at the oral part) at 5 dpf of Tg(hsp70: Gal4); Tg(UAS: ChR2-eYFP). The same gut before (r) and during (s) the irradiation with the spot of blue light. Kymographs at the solid and dashed red lines in (s, t). Schematic representation of the gut movement induced with the light (u). Asterisks indicate the lumen of the gut. Arrows indicate the movement of the gut. Scale bars, 20 μm. Also see Supplementary video 7.