The jellyfish's green fluorescent protein (GFP) already enables researchers to study proteins in a variety of cells. Until now, biologists had thought GFP-like proteins existed only in bioluminescent--or light-producing--organisms. But evolutionary biologist Yuli Labas of the Institute of Ecology and Evolution in Moscow suspected that the ability to generate light might have evolved from organisms that transform light into different wavelengths--that is, fluoresce. So his colleagues, Sergey Lukyanov and Mikhail Matz of the Institute of Bioorganic Chemistry, looked for GFP-like proteins in fluorescing corals.

The researchers scored hits in all five species studied, according to a report in the October issue of Nature Biotechnology. They speculate that such proteins, which may have given rise to GFP, are "dyes" that likely protect the corals from sunburn, says Matz. The scientists have applied for a patent on the proteins, which Matz says could lead to "new multicolor, in vivo labeling and detection systems." More colors could allow scientists to monitor more cellular players simultaneously, notes Columbia University geneticist Martin Chalfie. "The red looks like a very good addition," he says.