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Giant fish-killing water bug reveals ancient and dynamic venom evolution in Heteroptera

Walker, Andrew A., Hernández-Vargas, Maria José, Corzo, Gerardo, Fry, Bryan G., King, Glenn F.
Cellular and molecular life sciences 2018 v.75 no.17 pp. 3215-3229
Cimicidae, Lethocerus, Triatominae, antimicrobial peptides, bioactive properties, enzymes, feeding methods, hematophagy, herbivores, infrared spectroscopy, predation, proteins, proteomics, saliva, toxins, transcriptomics, venoms
True Bugs (Insecta: Heteroptera) produce venom or saliva with diverse bioactivities depending on their feeding strategies. However, little is known about the molecular evolution of the venom toxins underlying these biological activities. We examined venom of the giant fish-killing water bug Lethocerus distinctifemur (Insecta: Belostomatidae) using infrared spectroscopy, transcriptomics, and proteomics. We report 132 venom proteins including putative enzymes, cytolytic toxins, and antimicrobial peptides. Over 73% (96 proteins) showed homology to venom proteins from assassin bugs (Reduviidae), including 21% (28 proteins from seven families) not known from other sources. These data suggest that numerous protein families were recruited into venom and diversified rapidly following the switch from phytophagy to predation by ancestral heteropterans, and then were retained over > 200 my of evolution. In contrast, trophic switches to blood-feeding (e.g. in Triatominae and Cimicidae) or reversions to plant-feeding (e.g., in Pentatomomorpha) were accompanied by rapid changes in the composition of venom/saliva, including the loss of many protein families.