UCSD Scientists Transfer 4-Color Genetic Beacons
Call it Technicolor chemistry.
Take a firefly-like Jamaican beetle, figure out what part of its genetic structure produces the enzymes that make it light up in various colors, and stick the genes into bacteria. The goal: Bacteria that glow in four different colors.
That’s just what researchers at UC San Diego and Johns Hopkins University have achieved, two years after they used a similar technique to produce glow-in-the-dark tobacco plants, according to a report in today’s issue of Science magazine.
The bacteria glow green, yellow-green, yellow and orange, thanks to the genes from the luminescent Jamaican click beetle. This 1-inch-long distant relative of the firefly looks more like a housefly than it does a beetle.
The transfer of the beetle’s luminescent genes is more than a genetic engineer’s curiosity, the scientists say.
“These genes are potentially very valuable as research tools for tracking gene expression--that is, letting us know when genes are turned on or off--in living systems,” said Keith V. Wood, a chemistry doctoral student at UCSD and primary investigator on the project.
Biological Beacons
The light-emitting genes, which the scientists say attach readily to other genes, could serve as biological beacons when scientists want to simultaneously track the activity of several inserted genes. They also would allow researchers to track the fate of specific cells in the body or the spreading of genetically engineered microbes released into the environment.
The click beetle’s genes isolated by the UCSD-Johns Hopkins team regulate the production in its abdominal light organ of an enzyme called luciferase. Luciferase converts chemical energy into light when it is combined in the light organ with oxygen, the energy-storage molecule ATP and a substance in the insects called luciferin.
When inserted into other organisms, the low level of light the luciferase produces can be detected by X-ray film exposure or sensitive light-detection devices.
Luciferases in fireflies and the click beetle share only about 48% of the same protein structure, Wood said.
But the click beetle luciferases, although they produce four different colors, differ only slightly in structure. As a result, the researchers are now modifying the luciferase gene and enzyme structures to see if they can produce other colors of luminescence, said William D. McElroy, emeritus professor of biology at UCSD and a co-author of the report in Science.
Other authors are Y. Amy Lam, research associate in chemistry there, and Howard H. Seliger, professor of biology at Johns Hopkins University.
Two years ago, this same team inserted the firefly luciferase gene into tobacco plants. It sent out about 350 copies of the gene to researchers and biotechnology companies throughout the country, McElroy said.
The click beetle research grew out of 40 years of study of firefly luciferase chemistry by McElroy and his late wife, UCSD chemistry professor Marlene Deluca, McElroy said. They first discovered that they could collect and study the beetles when the insects, attracted to the light of McElroy’s cigar, began whacking into his face, he recalled Thursday.
“I had a cigar in my mouth, and here we saw something coming at the light from the cigar, and it was one of these charging click beetles,” he said. “They kept coming right at me.”
This habit of the beetles proved useful for collecting them, he said, because the insects proved virtually impossible to breed in captivity. For the current research, scientists collected the beetles in Jamaica and froze them for study.
