Modified cotton bug has killer sperm
Modified cotton bug has killer sperm
By Stephen Leahy
CROP insect pests genetically-modified to carry a lethal terminator gene that would help prevent their populations building up could soon be released into fields in the USA.
The first stage of field-testing could come as soon as this July, with the release into an Arizona cotton field of 2350 cotton-eating, pink bollworm moths that have been genetically engineered with a jellyfish gene.
The test would mark the worlds first field trial of transgenic insects and the first step in a new era in biocontrol called autocidal biocontrol.
The idea is to release modified male bollworms that have so-called killer sperm – sperm with an extra gene that prevents the formation of eggs in females.
"This is safer than looking for some new parasite to control bollworms," says Tom Miller, the lead researcher of the University of California transgenic bollworm team.
Over 200,000ha (500,000 acres) of US cotton is infested with bollworms, costing growers $30m a year, despite heavy pesticide use. GM Bt cotton is an effective control, but costs up to $74/ha ($30/acre) more than conventional cotton and faces resistance concerns.
The modified bollworms carry a jellyfish marker gene to make them glow green under fluorescent light, plus the lethal gene. But the lethal gene is conditional – if insects receive an antibiotic with their food they remain fully fertile, so numbers can be multiplied in the lab.
Once regular doses of the antibiotic stop a genetic switch flips and males start producing a protein in their sperm that prevents eggs from forming in females after mating.
"I did not think we would be here so fast, we got lucky," Prof Miller says of the relatively low-budget $1m project.
This summers Arizona field test is for bollworms with the jellyfish marker genes only, to see if they behave like normal bollworms and mate with native insects already present on the cotton. Researchers will track the spread of the marker gene. *
GMINSECTPESTS
• Cotton bollworm in USA.
• Modified to produce killer sperm.
• Would reduce populations.
• Field test of marker gene in July?
• Lethal gene needs more work.
• Significant approval concerns.