Fruit flies have complex eyes, but they do not have a better vision compared to simple eyes. For better sensing of light, they use six biological “Rhodopsin” type pigments in several ways. Even, three of them also have temperature sensing ability apart from light sensing. Now, scientists have discovered seventh pigment or Rhodopsin 7(Rh7) that regulates the day-night activity cycles in fruit fly brain.
A research team from the University of California started investigating the role of Rhodopsin 7. During the study, researchers replaced Rh1 with Rh7 with the genetic experiment to check the light-sensing ability in fruit fly eyes. In the journal of Nature, researchers explained that they have used electroretinogram to measure extracellular recording of a neural signal and found Rh7 is the functional alternative for Rh1.
Lead researcher and Professor of Molecular, Cellular and Developmental Biology at the University of California at Santa Barbara, Dr. Craig Montell said,“Rh7 is the first example of a rhodopsin that is important in setting circadian rhythms by being expressed in the central brain, rather than the eye”. He also explained that Rhodopsin 7 allows fruit fly brain to detect light in a more sensitive way and set circadian rhythms.
According to National Institutes of Health, scientists first found the existence of Rhodopsin in 1980 as a pigment for light-sensing and image formation in the brain. The previously known six rhodopsins work in the photoreceptor cell of a fruit fly so their genome also contains the sequence of seventh rhodopsin. However, the role of Rhodopsin 7 is still unclear.
Montell and his team performed several 12 hours of the day(light) and night(dark) tests and additional 20 hours of light tests in fruit fly to monitor their changes in behavior and how quickly they adjust to sudden changes of light. To track the expression pattern of Rhodopsin 7 researchers used Rh7 recognizing antibodies and found the expression in brain’s brain’s central pacemaker neurons.
The result shows flies that don’t have Rhodopsin 7 usually takes longer to adjustments. Researchers also gave sudden light pulses in the middle of the night to disrupt the normal circadian cycle and again found a fruit fly can adjust faster than other wild-flies as they have Rh7. generally, central pacemaker neurons have cryptochrome which acts as a light sensor. So, researchers genetically engineered some flies and deactivated the cryptochrome, but it can still adjust the changes of light. Researchers are suspecting that another molecule might be involved, and that turns out to be Rh7, which is more light-sensitive than cryptochrome.
