By a number of measures, spider silk is one of the toughest materials around. It's also light weight and (obviously) biocompatible. Unfortunately, it's also extremely hard to produce in any sort of usable quantity. Now, researchers have figured out a way that might help us make a lot more of something almost as good: they've engineered some DNA that encodes a hybrid of silkworm and spider proteins, and gotten silkworms to produce it.
We've cloned a number of spider silk proteins now, and managed to express them in everything from bacteria to goats. None of these methods end up making much in the way of protein, however, and the material that is made is difficult to purify and form into fibers. Spiders would seem like an obvious choice for making silk but they create a number of issues that we don't normally associate with manufacturing; as the authors put it, "territorialism and cannibalism preclude spider farming as a viable manufacturing approach."
In contrast, we've known how to work with silkworms for centuries and, in recent years, we've developed the ability to insert DNA into their genome. The animals can be grown in bulk, and they very conveniently place all of their silk into a cocoon that's easy to process. For all its appealing properties and commercial value, though, silk from silkworms doesn't have some of the better properties associated with spider silk.
Given all this, it's not a surprise that people have tried to get the genes for spider silk into silkworms. The resulting production, however, has been disappointingly low, and the silk hasn't had many of the properties that made anyone go through the effort of trying this in the first place.
In this case, the authors took a number of steps to integrate the DNA that encoded a spider silk gene a bit better in to the silkworm's regular biology. For starters, they added control sequences that ensured that their DNA construct was only expressed in the organs that make silk for the worm.
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