Using
an integrated transcriptomic and proteomic approach, we characterized
the venom peptidome of the European red ant, Manica rubida. We identified 13 “myrmicitoxins” that share sequence
similarities with previously identified ant venom peptides, one of
them being identified as an EGF-like toxin likely resulting from a
threonine residue modified by O-fucosylation. Furthermore,
we conducted insecticidal assays of reversed-phase HPLC venom fractions
on the blowfly Lucilia caesar, permitting us to identify
six myrmicitoxins (i.e., U3-, U10-, U13-, U20-MYRTX-Mri1a, U10-MYRTX-Mri1b, and U10-MYRTX-Mri1c) with an insecticidal activity. Chemically synthesized
U10-MYRTX-Mri1a, -Mri1b, -Mri1c, and U20-MYRTX-Mri1a
irreversibly paralyzed blowflies at the highest doses tested (30–125
nmol·g–1). U13-MYRTX-Mri1a, the
most potent neurotoxic peptide at 1 h, had reversible effects after
24 h (150 nmol·g–1). Finally, U3-MYRTX-Mri1a has no insecticidal activity, even at up to 55 nmol·g–1. Thus, M. rubida employs a paralytic
venom rich in linear insecticidal peptides, which likely act by disrupting
cell membranes.
In the mutualisms involving certain pseudomyrmicine ants and different myrmecophytes (i.e., plants sheltering colonies of specialized “plant-ant” species in hollow structures), the ant venom contributes to the host plant biotic defenses by inducing the rapid paralysis of defoliating insects and causing intense pain to browsing mammals. Using integrated transcriptomic and proteomic approaches, we identified the venom peptidome of the plant-ant Tetraponera aethiops (Pseudomyrmecinae). The transcriptomic analysis of its venom glands revealed that 40% of the expressed contigs encoded only seven peptide precursors related to the ant venom peptides from the A-superfamily. Among the 12 peptide masses detected by liquid chromatography-mass spectrometry (LC–MS), nine mature peptide sequences were characterized and confirmed through proteomic analysis. These venom peptides, called pseudomyrmecitoxins (PSDTX), share amino acid sequence identities with myrmeciitoxins known for their dual offensive and defensive functions on both insects and mammals. Furthermore, we demonstrated through reduction/alkylation of the crude venom that four PSDTXs were homo- and heterodimeric. Thus, we provide the first insights into the defensive venom composition of the ant genus Tetraponera indicative of a streamlined peptidome.
Stings of certain ant species (Hymenoptera: Formicidae) can cause intense, long-lasting nociception. Here we show that the major contributors to these symptoms are venom peptides that modulate the activity of voltage-gated sodium (NaV) channels, reducing their voltage threshold for activation and inhibiting channel inactivation. These peptide toxins are likely vertebrate-selective, consistent with a primarily defensive function. They emerged early in the Formicidae lineage and may have been a pivotal factor in the expansion of ants.
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