Glenn King of the University of Connecticut Health Center in Farmington and his colleagues recently identified a unique family of toxins in the venom of a funnel-web spider. These neurotoxins are lethal when injected into insect tissues, yet have no effect if eaten by insects or other animals (Nature Structural Biology, vol 7, p 505).
King's team is now engineering the gene for one of these toxins into baculoviruses, common viruses that infect certain moths and butterflies, and have long been used as "biopesticides". When the modified baculovirus infects an insect, the insect's cells should start to produce the toxin, killing it faster than wild viruses. Because the host dies quickly, before much virus can replicate, the modified virus shouldn't persist in the environment, say the researchers.
"I welcome a potentially environmentally friendly pest control but it's abundantly clear we need to be more firm about risk issues," comments George McGavin, an entomologist at Oxford University. "If we are not 100 per cent sure, it shouldn't be in the field."
There have already been several field trials worldwide of baculoviruses given a gene for a scorpion toxin (New Scientist, 21 January 1995, p 6). However, most of the scorpion toxin made in infected insects fails to fold into the correct shape, says King. By contrast, tests in bacteria suggest that almost 100 per cent of the spider toxin should fold properly, making the virus deadlier.
King thinks engineering toxin genes into viruses is preferable to adding them to plants, such as Bt maize. Not only does it mean that people do not have to eat plants that produce insecticidal toxins, but only target insects will be affected, he says. "These viruses can be exquisit
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Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-207-331-2751
New Scientist
13-Jun-2000