Scorpion venom is composed of a complex cocktail of poisonous peptides that immobilize animal prey on the spot. Some of the toxins in this cocktail, however, are only harmful to insects, which has prompted researchers to harness them to create a safe and ecologically sound pesticide.

Scientists from Tel Aviv University's Department of Plant Sciences have isolated the genetic sequences for important neurotoxins in the scorpion venom and have also developed methods to produce and manipulate toxins to restrict their toxicity in certain insects or mammals. The findings appear in a study published in Molecular Biology and Evolution.

Rather than isolating the venom constituents of the Israeli yellow scorpion, known to be among the world's most poisonous scorpions, researchers developed genetic methods for producing and manipulating the desired toxins in bacteria, then investigated how they act against insects and mammals, paving the way for potential use in the agriculture industry.

The team took this direction because attempts to insert a certain neurotoxin gene into a plant genome hoping for the plant to produce the toxin and kill infesting insects has failed. As a peptide, the toxin was metabolized in the insect guts, which evidently seems to require that it first be engineered to be able to penetrate into the insect blood stream to have its impact on the nervous system.

Some neurotoxins in the scorpion are highly active against some insects-- leaf-eating moths, locusts, flies and beetles but have no effect on beneficial insects like honeybees or on mammals like humans.

Since scorpion toxins must be modified to be able to penetrate the blood stream of an infesting insect, it is important to study the toxins and the way they interact with the insect nervous system. Only then would it be possible to modify them in such a way as to reach their target tissues in insects, researchers say.

The agriculture industry already uses mostly pyrethroids, which also penetrate into insects and attack their nervous systems, leading to paralysis and death. Their main drawback, however, is the lack of specificity and the danger these compounds pose to the environment, livestock and humans.

Citation: H. Weinberger et al., 'Positions under positive selection - key for selectivity and potency of scorpion {alpha}-toxins' Mol. Biol. Evol. Online, December 17, 2009; doi:10.1093/molbev/msp310