toxins Article Identification and Functional Characterization of a Novel Insecticidal Decapeptide from the Myrmicine Ant Manica rubida John Heep 1 , Marisa Skaljac 1 , Jens Grotmann 1, Tobias Kessel 1, Maximilian Seip 1, Henrike Schmidtberg 2 and Andreas Vilcinskas 1,2,* 1 Branch for Bioresources, Fraunhofer Institute for Molecular Biology and Applied Ecology (IME), Winchesterstrasse 2, 35394 Giessen, Germany;
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[email protected] (M.S.) 2 Institute for Insect Biotechnology, Justus Liebig University of Giessen, Heinrich-Buff- Ring 26-32, 35392 Giessen, Germany;
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[email protected]; Tel.: +49-641-99-37600 Received: 26 August 2019; Accepted: 23 September 2019; Published: 25 September 2019 Abstract: Ant venoms contain many small, linear peptides, an untapped source of bioactive peptide toxins. The control of agricultural insect pests currently depends primarily on chemical insecticides, but their intensive use damages the environment and human health, and encourages the emergence of resistant pest populations. This has promoted interest in animal venoms as a source of alternative, environmentally-friendly bio-insecticides. We tested the crude venom of the predatory ant, Manica rubida, and observed severe fitness costs in the parthenogenetic pea aphid (Acyrthosiphon pisum), a common agricultural pest. Therefore, we explored the M. rubida venom peptidome and identified a novel decapeptide U-MYRTX-MANr1 (NH2-IDPKVLESLV-CONH2) using a combination of Edman degradation and de novo peptide sequencing. Although this myrmicitoxin was inactive against bacteria and fungi, it reduced aphid survival and reproduction.