Drugs from bugs : venomics of predatory heteroptera

The true bugs (Heteroptera) represent a hyper-diverse suborder of insects that inhabit a wide range of habitats around the world. They inject protein-rich saliva into their food, pre-digest it, and take up the liquefied components. Predatory Heteroptera have evolved venomous saliva, which enables them to overwhelm, kill and pre-digest animal prey, in some cases many times larger than themselves. However, the protein composition and activity of most true bug venoms is unknown and their role in the adaptation of true bugs to new ecological niches has not been studied in detail. This thesis aims to identify differences in venom composition, activity and deployment between heteropteran species occupying different ecological niches, using a proteotranscriptomic and bioassay-based approach. It shows that venom composition and activity differ interspecifically and likely reflect adaptions to the microhabitat, feeding style and foraging strategy of different heteropteran species. More in-depth analysis of venom from the African assassin bug Psytalla horrida, using cation-exchange chromatography and bioassays, revealed that redulysins and the uncharacterized venom protein family 2 play a key role in antimicrobial defense, prey overwhelming, prey killing and/or liquefaction. This work contributes to a better understanding of the ecology of predatory Heteroptera and provides new insights into venom functions and novel compounds.