The Predatory Stink Bug Arma custos (Hemiptera: Pentatomidae) Produces a Complex Proteinaceous Venom to Overcome Caterpillar Prey

SIMPLE SUMMARY: We studied the salivary venom of a predatory stink bug, which captures prey by injecting venom through their specialized stylets. We aimed to understand the composition and function of the salivary venom, which had previously been poorly characterized. We collected gland extracts and venom samples from a stink bug and performed shotgun proteomic and transcriptomic analyses. The results showed that the salivary venom of the stink bug contained over 100 individual proteins, including various enzymes and proteins with different functions, but did not contain the proteins that were shared by and unique to other predatory heteropterans. The most abundant families of proteins in the salivary venom were hydrolase enzymes. We also found that the proteinaceous (>3 kDa) venom fraction of the stink bug had insecticidal activity against caterpillars. Our findings increase the understanding of salivary proteins in predatory stink bugs and suggest an innovative strategy of using these proteins to develop bioinsecticides. ABSTRACT: Predatory stink bugs capture prey by injecting salivary venom from their venom glands using specialized stylets. Understanding venom function has been impeded by a scarcity of knowledge of their venom composition. We therefore examined the proteinaceous components of the salivary venom of the predatory stink bug Arma custos (Fabricius, 1794) (Hemiptera: Pentatomidae). We used gland extracts and venoms from fifth-instar nymphs or adult females to perform shotgun proteomics combined with venom gland transcriptomics. We found that the venom of A. custos comprised a complex suite of over a hundred individual proteins, including oxidoreductases, transferases, hydrolases, ligases, protease inhibitors, and recognition, transport and binding proteins. Besides the uncharacterized proteins, hydrolases such as venom serine proteases, cathepsins, phospholipase A(2), phosphatases, nucleases, alpha-amylases, and chitinases constitute the most abundant protein families. However, salivary proteins shared by and unique to other predatory heteropterans were not detected in the A. custos venom. Injection of the proteinaceous (>3 kDa) venom fraction of A. custos gland extracts or venom into its prey, the larvae of the oriental armyworm Mythimna separata (Walker, 1865), revealed insecticidal activity against lepidopterans. Our data expand the knowledge of heteropteran salivary proteins and suggest predatory asopine bugs as a novel source for bioinsecticides.