INSECT IMMUNITY - SEPTIC INJURY OF DROSOPHILA INDUCES THE SYNTHESIS OF A POTENT ANTIFUNGAL PEPTIDE WITH SEQUENCE HOMOLOGY TO PLANT ANTIFUNGAL PEPTIDES

In response to a septic injury (pricking with a bacteria-soaked needle ) larvae and adults of Drosophila produce considerable amounts of a 44 -residue peptide containing 8 cysteines engaged in intramolecular disu lfide bridges, The peptide is synthesized in the fat body, a functiona l homologue of the mammalian liver, and secreted into the blood of the insect. It exhibits potent antifungal activity but is inactive agains t bacteria, This novel inducible peptide, which we propose to name dro somycin, shows a significant homology with a family of 5-kDa cysteine- rich plant antifungal peptides recently isolated from seeds of Brassic aceae, This finding underlines that plants and insects can rely on sim ilar molecules in their innate host defense.