Ecdysone and insect immunity: the maturation of the inducibility of the diptericin gene in Drosophila larvae.

The developmental analysis of the inducibility of the Drosophila diptericin gene promoter as a response to septic injury shows an important increase in the response during the third larval instar leading to a maximum in late larvae and early prepupae. This increase, or maturation, is temporally correlated with known ecdysone induced events of the salivary gland and we now present evidence, using wild type and mutant larvae, that it does indeed depend upon ecdysone. The response remains minimal in larvae carrying either the temperature sensitive ecdysone deficient late larval lethal allele ecd1, or l(1)t187, a deep orange allele known to be deficient in the ecdysone response. However, experiments with the late larval lethal Broad-Complex mutant l(1)t435 show that the regulation of this response is distinct from the developmental ecdysone regulated hierarchies.