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. 2000 Mar 21;97(7):3376–3381. doi: 10.1073/pnas.070357597

Figure 1.

Figure 1

Induction of antimicrobial peptide genes after Ecc-15 infection. (A) Viable Ecc-15 is required to induce a larval immune response. Quantitative measurements of β-galactosidase activity in larvae carrying either the dipt-lacZ (Left) or the drom-lacZ (Right) reporter genes were performed on five larvae collected 24 h after various treatments. Each bar represents an independent measurement; mean and SD are indicated above. C, control larvae incubated in banana alone; 15 and 2046, larvae naturally infected with Ecc-15 and Ecc-2046, respectively; 15-HK, heat-inactivated Ecc-15 (40 min at 70°C); 15-BI, larvae injected with Ecc-15 (bacterial injection). (B) Northern blot analysis shows that Ecc-15 infection induces sustained diptericin expression in larvae and pupae collected at different time intervals after natural infection by Ecc-15. L3, third instar larvae; P, pupae; C, control. (C) Northern blot analysis shows that Ecc-15 infection of larvae induces the expression of all of the antimicrobial genes. Total RNA was collected 24 h after infection, and the blot was hybridized successively with the following cDNA probes: diptericin (dipt), cecropin A1 (cec A), attacin (att), drosomycin (drom), and ribosomal protein 49 (rp49) as an internal control. C, control larvae incubated with only banana; NI, larvae incubated with Ecc-15 (natural infection); BI, third instar larvae injected with Ecc-15 (bacterial injection). (D) Ecc-15 induces a systemic immune response. Histochemical staining of β-galactosidase activity is shown in the fat body of wild-type (OrR) and imd homozygous larvae that were collected 24 h after infection and that carry the dipt-lacZ, cec-lacZ, or drom-lacZ reporter genes. Ecc-15 infection induces high expression of all three reporter genes in fat bodies from wild-type larvae. The absence of β-galactosidase activity in fat bodies isolated from infected imd larvae carrying the dipt-lacZ and cec-lacZ genes indicates that the induction of cec-lacZ and dipt-lacZ expression by Ecc-15 requires the imd gene product.