Spider venom insecticide
A chemical in tarantula venom that can kill insect pests when they eat it, and might be useful as an environmentally-friendly insecticide, has been discovered by scientists in Australia.
Spider venom consists of a cocktail of hundreds, and even thousands, of different protein molecules that attack and neutralise the nervous systems of prey in a variety of different ways.
This massive case of overkill is driven in part by the fact that spiders consume a wide range of species, and a toxic mixture of this magnitude is almost guaranteed to work against most things. It's also very difficult for prey species to evolve resistance to a venom that works in so many different ways at once.
As such, scientists regard spider venom as a rich source of potential insecticides, which would have the added advantage of being more environmentally friendly.
But because spiders have fangs to inject this lethal mixture, researchers had broadly assumed that the venom components would not work if they were merely eaten by a pest.
Now a study by University of Queensland biologist Glenn King and his colleagues, published this week in PLoS One, has uncovered an orally-active spider venom component, equivalent in potency to current synthetic insecticides, that might fit the bill.
Venom harvested from the Australian tarantula Selenotypus plumipes was separated into its component chemicals using a technique called chromatography.
Each of these components was then tested individually for toxicity by offering food laced with it to termites, mealworms and cotton bollworms.
One substance, which the team dubbed OAIP or orally-active insecticidal peptide, was powerfully active, which the researchers put down to the fact that the molecule has lots of cross-links binding it together, enabling it to resist the harsh environment of the insect digestive tract. This also means that the molecule is very stable in the environment, remaining intact for at least 7 days at 22°C.
The team don't yet know how the agent works, but, structurally, it bears a resemblance to venom components that are known to target neurones, and tests on treated insects suggests that it lethally over-activates the nervous system.
Armed with the chemical structure of OAIP, the team were then able to track down the gene used by the spider to make the substance. Plants endowed with this gene by GM techniques, they speculate, would be lethal for any insects that tried to eat them, while pollinators and other harmless species shouldn't be harmed, although this remains to be tested.
Reassuringly, the venom is also harmless to humans...