PG–The research team (which includes Randy Lewis, who was involved in the first deciphering of the structure of spider dragline silk protein in 1990) actually introduced a synthetic spider silk gene into the silkworms, rather than a natural one. They synthesized it by combining stretches of flagelliform silk gene (which dictates the super-stretchy silk protein orb weavers use to make the capture spiral in the orb) with stretches of major ampullate spidroin 2 gene, which dictates one of the components of dragline silk, which is very strong. It’s really clever research: they not only synthesized this gene, but also strategically introduced it into the silkworm silk gene at a position they thought most likely to promote good fiber formation. I don’t fully understand everything they did here (I’m the English major part of our writing team), but they’ve put together a multitude of genetic engineering techniques and I’m sure they’re learning just as much from what’s not working as from what is. Even if they never get real spider silk out of silkworms, getting enhanced silkworm silk may be good enough for many applications.

It appears that the spider silk genes originated in Nephila clavipes, one of the golden orb weavers. They produce very strong major ampullate silk. They also produce it in large quantities (they’re big spiders) so they were favorites in the early days of silk research partly just because they provided large samples and they’re easier to dissect. As researchers understand more, and as it gets cheaper to conduct this kind of analysis (due to technology advances), more silk proteins and genes from more spider species are being studied. Different silks have different properties. None of them are going to be easy to reproduce.

Are people patenting these hybrid lines? My first thought would be obviously.

Thanks, great stuff, I am going to check out your book as well.

It’s worth remembering that spiders, unlike silkworms, make a number of different silks, the number depending on where a species is on the spider evolutionary tree. An orb web weaver can make more than 6 different silk proteins. Industrially focused research is usually interested in dragline silk and sometimes flagelliform silk, which is the silk found in the capture spiral of orb webs. Lately, there’s also interest in the aggregate silk protein glue that araneoid spiders deposit on their flagelliform lines.

But thousands of spider species who can’t make flagelliform or aggregate silk proteins make cribellate silk, which also sticks to insects. And thousands of other species can’t make cribellate or flagelliform or aggregate silk proteins but still do fine. The evolutionary development of all this stuff is fascinating.