Bioinsecticides from spider venom

For an insecticide to be effective it needs to be orally active. Spider-venom peptides have previously been dismissed as potential insecticides because they are toxic only when injected into prey via fangs. Now, a newly discovered protein in the venom of Australian tarantulas (Selenotypus plumipes) has proven otherwise - it kills insects that eat it.

Professor Glenn King and Dr Maggie Hardy from the Institute of Molecular Bioscience at the University of Queensland and colleagues isolated the small protein, called orally active insecticidal peptide-1 (OAIP-1), and found it to be highly toxic to insects that consumed it. They also found that OAIP-1 has that same potency as the pyrethroid insecticides and acts synergistically with neonicotinoid insecticides.

“There is an urgent need for new insecticides due to insects becoming resistant to existing products and others being deregistered due to perceived ecological and human health risks,” King said.

In particular, OAIP-1 is strongly insecticidal to the cotton bollworm (Helicoverpa armigera), an important agricultural pest. It is also effective against termites and mealworms.

The cotton bollworm and other insect pests reduce global crop yields by 10-14% annually, damage 9-20% of stored food crops as well as spread a variety of diseases. Several species are resistant to currently available insecticides.

“Cotton bollworms cause major economic damage to crops and the toxin we have isolated is more potent against these insects than existing chemical insecticides,” said King.

King said OAIP-1 could be developed into an environmentally friendly insecticide as it was expected the toxin would degrade into innocuous breakdown products in the environment.

“Our study indicates it is possible to isolate insecticidal compounds with high levels of oral activity from the venom of spiders and most likely other venomous animals that prey on insects, such as centipedes or scorpions,” Hardy said.

Using NMR spectroscopy, the team determined the three-dimensional structure of the protein and found that three disulfide bonds formed a structural motif that gives the peptide a high level of biological stability, which probably contributes to its oral activity.

“The next step is to determine the safety of OAIP-1 for non-target organisms, including pollinators, like bees, as well as natural enemies of insect pests such as ladybird beetles.”

Alternatively, the authors suggest the genes encoding these peptides could be used to engineer insect-resistant plants or enhance the efficacy of microbes that attack insect pests.

This research was published in PLOS ONE.