Diptericin-like protein: an immune response gene regulated by the anti-bacterial gene induction pathway in Drosophila.

Insects produce various anti-microbial peptides in response to injury and infection. In Drosophila, diptericin has previously been studied as an anti-bacterial immune response gene. Here, we report the cloning of the diptericin-like protein (dptlp) gene as a paralog of Drosophila diptericin. By comparison of their sequences, we found that the dptlp gene has all of the functional domains conserved in the diptericin gene and other anti-bacterial proteins. The dptlp gene was rapidly induced by bacterial infections and showed different time-dependent gene expression patterns from those of diptericin. Like diptericin, dptlp was specifically produced from the fat body, and its expression was strictly dependent on bacterial infections. In addition, the dptlp gene expression was almost completely abolished in the imd mutant, which implicates that its expression is regulated by the anti-bacterial arm of the Drosophila innate immune regulatory pathways. In support of this, we found GATA, interferon consensus responding element, and kappa B binding sites, which is known to be important for the proper expression of anti-bacterial genes, in the proximal promoter region of the dptlp gene. Taken together, our findings support that dptlp is a novel anti-bacterial peptide whose expression is regulated by the anti-bacterial immune response mechanism.