Ance is a single domain homologue of mammalian angiotensin-converting enzyme (ACE) and is important for normal development and reproduction in Drosophila melanogaster. Mammalian ACE is responsible for the synthesis of angiotensin II and the inactivation of bradykinin and N-acetyl-Ser-Asp-Lys-Pro, but the absence of similar peptide hormones in insects suggests novel functions for Ance. We now provide evidence in support of a role for Ance during Drosophila metamorphosis. The transition of larva to pupa was accompanied by a 3-fold increase in ACE-like activity, which subsequently dropped to larval levels on adult eclosion. This increase was attributed to the induction of Ance expression during the wandering phase of the last larval instar in the imaginal cells (imaginal discs, abdominal histoblasts, gut imaginal cells and imaginal salivary gland). Ance expression was particularly strong in the presumptive adult midgut formed as a result of massive proliferation of the imaginal midgut cells soon after pupariation. No Ance transcripts were detected in the midgut of the fully differentiated adult intestine. Ance protein and mRNA were not detected in imaginal discs from wandering larvae of flies homozygous for the ecd1 allele, a temperature-sensitive ecdysone-less mutant, suggesting that Ance expression is ecdysteroid-dependent. Physiological levels of 20-hydroxyecdysone induced the synthesis of ACE-like activity and Ance protein by a wing disc cell line (Cl.8+), confirming that Ance is an ecdysteroid-responsive gene. We propose that the expression of Ance in imaginal cells is co-ordinated by exposure to ecdysteroid (moulting hormone) during the last larval instar moult to increase levels of ACE-like activity during metamorphosis. The enzyme activity may be required for the processing of a developmental peptide hormone or may function in concert with other peptidases to provide amino acids for the synthesis of adult proteins.
Abbreviations used: ACE, angiotensin converting enzyme; Ance, Drosophila angiotensin-converting enzyme; LSP, larval serum proteins; PPF, post-puparium formation.
These authors contributed equally to this study.