Fig. 5: Mobilization of stored Ca²⁺ through Capa–CapaR is crucial to surviving Ca²⁺ deficiency.

a–c, Ca²⁺ stored in the MT was mobilized in a CapaR-dependent manner under Ca²⁺-deficient conditions. a, Schematic of rearing larvae on SHM or CFHM from 0 h AL3E. b,c, The A-MT Ca²⁺ content (b) and survival rate (PF rate) (c) for control or CapaR RNAi (CapaR-i) larvae reared on SHM or CFHM. d–f, Specific knockdown of Capa in the VaNs disrupted haemolymph Ca²⁺ homeostasis in wandering L3 larvae. d, Schematic of rearing larvae on HM containing varying amounts of Ca²⁺ from 0 h AL3E. e,f, The haemolymph Ca²⁺ concentration (e) and survival rate (PF rate) (f) for control or Capa RNAi larvae reared on HM containing varying amounts of Ca²⁺. g–j, Feeding larvae a high-Ca²⁺ diet rescued the elongated pupal phenotype induced by Capa RNAi. g, Schematic of rearing larvae on standard fly food (SFF), high-Ca²⁺ food (HCF) and high-Mg²⁺ food (HMF) from 0 h AL3E. h, Representative images of control or Capa RNAi pupae reared on SFF or food supplemented with 50 mM CaCl₂ (HCF) or 50 mM MgCl₂ (HMF). Scale bar, 1 mm. i, The pupal axis ratio of control or Capa RNAi pupae reared on SFF (0 mM) or food supplemented with 10, 25 or 50 mM CaCl₂. j, The haemolymph Ca²⁺ concentrations for control or Capa RNAi wandering L3 larvae reared on SFF or food supplemented with 50 mM CaCl₂ (HCF). CapaR-Gal4^TS>UAS-dicer2 was used as an IS driver, and R18D09∩R54A09-Gal4^TS was used as a VaN-specific driver. Data are mean ± s.d. Sample sizes (n) and P values (P < 0.05) are shown in the graphs. Statistical analysis was performed using two-way (b, c, e, f and i) and one-way (j) ANOVA with Tukey’s multiple-comparison test; *P < 0.0001; NS, not significant (P > 0.05).

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