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Scientists enable 'blind' flies to see colors (3/31/98)

A portion of the color vision system of honeybees has been successfully transferred to fruit flies by molecular biologists at The University of Texas Health Science Center at San Antonio.

The project is chronicled in the April issue of The Journal of Neuroscience. "This has never been done before, " said Steven G. Britt, MD, assistant professor of molecular medicine at the Health Science Center and one of the authors. "The first bee color vision genes were discovered in 1996 but no one had taken this step."

Two different visual pigment genes from the eyes of honeybees (Apis mellifera) were introduced into specially bred fruit flies (Drosophila). The fruit flies lacked complete visual pigment genes, while the inserted genes encoded for pigments sensitive to blue or ultraviolet (UV) light.

Employing sophisticated laboratory procedures, the scientists first demonstrated that the eyes of normal fruit flies strongly responded to flashes of light at different wavelengths. They confirmed that another group of "blind" flies did not respond. Last, strains of flies expressing the genes from honeybees were found to show sensitivity to the blue and UV ranges of light.

"We have shown that the honeybee's blue- and UV-sensitive opsins [visual pigments] are biologically active when expressed in the R1-6 photoreceptor cells of blind fruit flies and are capable of restoring the light response of these mutant animals," said Steven M. Townson, PhD, postdoctoral fellow in the molecular medicine department and lead author of the new paper.

The study findings may enable scientists to work out new ways of testing how color discrimination works at the molecular level. Such results are of high importance to many scientists and may one day lead to understandings that could result in procedures to improve human color vision.

Much of the work was done at the Health Science Center's Institute of Biotechnology in the Texas Research Park west of San Antonio. Researchers from the university's department of molecular medicine collaborated with two scientists from the organismic and evolutionary biology department at Harvard University. The project was supported by a grant from the National Eye Institute and a postdoctoral fellowship from Prevent Blindness America to Dr. Townson.

In the 1910s, bees were shown to use color in foraging on flowers. A German scientist, Karl von Frisch, actually trained bees to go to flowers of particular colors. "Because we know bees can do this, they make good subjects for experiments on the molecular basis for color vision," Dr. Britt said. "Bees and fruit flies ar e excellent model systems for study."

"Color vision is one of the most familiar forms of stimulus discrimination," the authors reported. "The ability of an organism to discriminate differences in wavelength distribution within the environment and to use this information to direct its behavior enables it to select food sources, avoid unsafe environments and predators, and identify conspecifics (members of its own species) and potential mating partners."

The Journal of Neuroscience's cover photo of a bee hovering next to a Texas bluebonnet was taken by Wen-Hai Chou, graduate student in molecular medicine.

Contact: Will Sansom (210) 567-2570