Figure 5.

Regulation of Ilp7 Neuronal Activity by Nutrients and Hypoxia, and Its Effect on Tracheal Branching

(A) Exposure to yeast leads to a transient Ca²⁺ rise in Ilp7 neurons. Activity returns to basal levels after one minute. No such response is observed in control Va neurons.

(B) A switch from 21% to 1% ambient O₂ elicits a rapid rise in Ca²⁺ in Ilp7 neurons that persists while O₂ is low. Upon return to normoxia, the basal activity of the Ilp7 neurons is immediately abrogated. No Ca²⁺ rise is triggered in control Va neurons, which display a subtle drop in Ca²⁺ levels in response to hypoxia, as has previously been observed for different types of neurons in various species (Cheung et al., 2006, Fujiwara et al., 1987, Krnjević, 1999). Error bars denote SEM.

(C and D) False color-coded single frames depicting GCaMP fluorescence in representative movies illustrating the response to yeast (C) or hypoxia (D) observed in Ilp7 neuronal cell bodies. Yellow/white indicates strong responses, red, low Ca²⁺ (false color scale is shown to the left).

(E and F) 25°C thermogenetic activation of the TrpA1 channel expressed in Ilp7 neurons through larval development results in increased tracheal coverage of the midgut (F) relative to controls (E for GAL4 control). Quantifications are displayed to the right of these two panels (p < 0.001 versus GAL4 control, p < 0.0001 versus UAS control, n = 23-27/set).

Scale bars, 25 μm (C) and (D) or 10 μm (E) and (F). See also Figure S6.