Science: Of Fireflies and Tobacco Plants

It sounds like a child's riddle: What do you get when you cross a firefly with a tobacco plant? Answer: tobacco that lights itself. That is essentially what a team of scientists at the University of California at San Diego has done. By outfitting a fragment of a plant virus with the gene that tells firefly cells to produce a protein central to generating light, the researchers have created a plant that literally glows in the dark.

The technique, reported in last week's issue of the journal Science, is significant not so much as a demonstration of virtuoso genetic engineering, but...