Parasitoid wasps are large group of wasps which rarely sting humans but can be ruthless towards other insects. As parasitoids, they lay their eggs on or in insect hosts. Their larvae feed on the host, growing until they reach full development and eventually kill the host.  

To support their gory reproduction, parasitoid wasps have developed a devious armoury of chemicals, many of which are peptides, to inject into their host. The mixture includes venom peptides, viruses and other regulatory factors, which work to hijack the physiology of the host and transform it into a suitable environment for larval development. Until recently, little was known about the exact structures and functions of the peptides produced in this complex mixture.  

Last year, Dr Andrew Walker, CI Glenn King and their collaborators selected four key peptides produced by the parasitoid wasp Cotesia flavipes to study further. As venoms are known to be a good source of insecticides and medicines, the research team were interested to determine whether this wasp produced any potentially useful molecules. 

To gain enough for testing, the peptides were produced in the laboratory either by chemical synthesis or bacterial expression. The peptides were tested in wasp host systems, as well as against pathogens and in human cells. It was confirmed that the peptides interacted with the immune system of their host, reducing their ability to recognise and destroy foreign objects, thus promoting the survival of injected wasp eggs. Interestingly, two of the peptides were not toxic to humans and were shown to kill Candida albicans, a common fungus that causes infection in humans. Additionally, three of the peptides showed insecticidal activity, including against the sugarcane borer Diatraea saccharalis and the fall armyworm Spodoptera frugiperda, which destroys a wide variety of crops.  

The work in this study highlights the potential use of parasitic wasp-produced peptides as biofriendly insecticides and anti-fungal treatments. Perhaps the parasitic wasp might not be so wicked after all! 

Reference: https://onlinelibrary.wiley.com/doi/full/10.1111/1744-7917.13154