Figure 3.

Systemic induction of drosomycin after sterile wounding. In situ hybridization of (A) unwounded, (B) wounded wild-type (WT) and (C) srp mutant embryos shows that Drs is upregulated in the yolk after injury independent of haemocytes. (D,E) High-magnification view to compare Drs expression in the yolk of an unwounded and wounded embryo. (F–I) A Drs-GFP reporter line (colour inverted) shows that from stage 17, the fat body also upregulates Drs after laser wounding of (G) wild-type, (H) srp and (I) Toll mutants. (J) A methylene blue-stained resin section through a 90 min wound with recruited haemocytes indicated by arrows (top panel). The inset corresponds to an electron microscopic view (lower panel) illustrating how the vitelline membrane (indicated by the asterisk) remains intact beyond the epithelial wound edge (arrowhead). Scale bar, 5 μm. (K) Wound severity correlates with fat body expression of Drs. Two large wounds induced the Drs reporter in 84% of embryos, one large wound induced 66%, one small wound 43% and one small wound+Staphylococcus aureus 35%. GFP-moesin embryos were wounded to highlight wound sizes. Drs, drosomycin; GFP, green fluorescent protein; srp, serpent.