The researchers observed that, in mutant flies that have a non-functioning Rhodopsin6 (green-sensitive) gene, the photoreceptors that would have normally produced this Rhodopsin instead slowly start to make the blue-sensitive Rhodopsin5. After two weeks, essentially all of these photoreceptors were observed making the blue Rhodopsin. The authors named one of the mutations in Rhodopsin6 gene "Frank Sinatra" because presumably it makes old eyes more sensitive to blue lightthey don't actually become blue in color.
These findings showed, then, that in normal flies, green Rhodopsin6 maintains repression of the blue Rhodopsin5 gene. This result is surprisingpreviously, it had not been known that Rhodopsins could control how other Rhodopsins are made.
The neurons governing our sense of smell are organized in a similar fashion. Once each olfactory neuron, which is responsible for this sense, makes a functional olfactory receptor protein, that receptor can prevent other genes encoding different olfactory receptors from being turned on in the same cell.
While the researchers did not investigate what brings about this change in Rhodopsins, they think of this as a maintenance mechanism that prevents cells from having blue and green Rhodopsins together.
"The two types of photoreceptors could be connected to different neuronal circuits in the brain which interpret the information they receive from photoreceptors as being about blue or green light," noted Daniel Vasiliauskas, the leading author of the paper and a post-doctoral fellow at NYU. "Thus changing the Rhodopsin that a photoreceptor make
|Contact: James Devitt|
New York University