A Silky Revolution

Genetically modified silk wasn't in vogue on fashion runways this season, but a designer strain of glow-in-the-dark silkworms suggests that such fabrics may soon be feasible. The fluorescent insects are a first step toward producing strains of silkworms that resist disease or spin thread that, for instance, is tougher than natural silk or even glows in the dark.

Scientists figured out how to insert foreign genes into fruit flies nearly 20 years ago, and other teams have managed since then to insert genes into mosquitoes and even beetles. However, the glow-in-the-dark silkworms (Bombyx mori) are the first lepidopterans (the order that includes moths and butterflies) to receive artificial genes. In the January issue of Nature Biotechnology, geneticist Pierre Couble of the CNRS Center for Molecular and Cellular Genetics in Villeurbanne, France, and his colleagues from Japan and the United States describe how they inserted the gene for green fluorescent protein (GFP), originally isolated from jellyfish, into silkworms.

To slip the gene into the insect's genome, the team inserted it into a stretch of DNA called a transposable element, which can move from one place on the genome to another. The team then injected this DNA construct into fertilized silkworm eggs and found that about 2% of the resulting larvae were fluorescent, demonstrating that the insects were making the GFP. The offspring of those moths also carried the gene and could produce glow-in-the dark offspring of their own.

Couble says the team is now trying to insert genes that will be turned on specifically in the silk glands of the worms, with the hope of producing genetically modified fibers. The team's first project is glow-in-the-dark silk; if that effort succeeds, says entomologist and molecular biologist Peter Atkinson of the University of California, Riverside, scientists might someday be able to engineer silkworms that produce spider silk. So far, chemists have failed in attempts to make an artificial version of this extremely strong natural fiber, which could find use in bulletproof vests, for example.

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