Figure 2.

Time-course analysis of antimicrobial gene expression after infection by various microorganisms. (A) Northern blot of total RNA extracted from female wild-type (Oregon^R) adults at different time intervals after challenge (as indicated). Adult flies infected by pricking under the same conditions were kept at 29°C. The blot was successively hybridized with the following cDNA probes: diptericin (Dipt), cecropin A1 (Cec A), attacin (Att), drosocin (Drc), defensin (Def), metchnikowin (Metch), drosomycin (Drom), and rp49 (Rp49). Unchallenged females show a low level of drosomycin gene expression due to the constitutive expression in the sperm storage structures (D. Ferrandon, personal communication). This experiment was repeated several times and yielded similar results. (B) The signals on Northern blots of Fig. 3A were quantified by a Bioimager system. The values were normalized with the corresponding value of rp49. The highest level of expression in a series was normalized as 100, and the results are given in relative activity (percent). Results obtained for defensin were similar to those for diptericin (data not shown).