NOVEL INDUCIBLE ANTIBACTERIAL PEPTIDES FROM A HEMIPTERAN INSECT, THE SAP-SUCKING BUG PYRRHOCORIS-APTERUS

Insects belonging to the recent orders of the endopterygote clade (Lep idoptera, Diptera, Hymenoptera and Coleoptera) respond to bacterial ch allenge by the rapid and transient synthesis of a battery of potent an tibacterial peptides which are secreted into their haemolymph. Here we present the first report on inducible antibacterial molecules in the sap-sucking bug Pyrrhocoris apterus, a representative species of the H emiptera, which predated the Endopterygotes by at least 50 million yea rs in evolution. We have isolated and characterized from immune blood of this species three novel peptides or polypeptides: (i) a 43-residue cysteine-rich anti-(Gram-positive bacteria) peptide which is a new me mber of the family of insect defensins; (ii) a 20-residue proline-rich peptide carrying an O-glycosylated substitution (N-acetylgalactosamin e), active against Gram-negative bacteria; (iii) a 133-residue glycine -rich polypeptide also active against Gramnegative bacteria. The proli ne-rich peptide shows high sequence similarities with drosocin, an O-g lycosylated antibacterial peptide from Drosophila, and also with the N -terminal domain of diptericin, an inducible 9 kDa antibacterial pepti de from members of the order Diptera, whereas the glycine-rich peptide has similarities with the glycine-rich domain of diptericin. We discu ss the evolutionary aspects of these findings.