Metchnikowin, a Novel Immune‐Inducible Proline‐Rich Peptide from Drosophila with Antibacterial and Antifungal Properties

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Abstract
One of the characteristics of the host defense of higher insects is the rapid and transient synthesis of a variety of potent antimicrobial peptides. To date, several distinct inducible antimicrobial peptides or peptide families have been totally or partially characterized. We present here the isolation and characterization of a novel 26‐residue proline‐rich immune‐inducible peptide from Drosophila, which exhibits both antibacterial (Gram‐positive) and antifungal activities. Peptide sequencing and cDNA cloning indicate the presense of two isoforms in our Drosophila OregonR strain, which differ by one residue (His compared to Arg) as a consequence of a single nucleotide change. The gene, which maps in position 52A1‐2 on the right arm of the second chromosome, is expressed in the fat body after immune challenge. The novel peptide, which we propose to name metchnikowin, is a member of a family of proline‐rich peptides, and we discuss the possible evolutionary relationships within this family.