View Program - 63rd Annual Drosophila Research Conference

Circadian rhythms are 24 hour cycles that align behavior, physiology, and gene expression with predictable daily changes in the environment. The primary entrainment cue for endogenous circadian clocks is light. Herein, we sought to test the impact of individual rhodopsins, the light-sensing G-protein-coupled receptors primarily expressed in the eye, on circadian rhythms. We found that flies harboring mutations in rhodopsin 3 (rh3), which is expressed in a subset of R7 photoreceptor cells, have an elongated circadian periodicity. Under constant darkness, wild-type flies maintain a locomotor rhythm with a 24 hour periodicity, whereas the rhythm of rh3 flies is dramatically extended to ~28 hours. This defect in rh3 flies suppresses the morning and evening anticipatory locomotion that usually precedes changes from lights on to lights off. Furthermore, the timing of sleep and feeding is also disrupted in rh3 flies. These defects in circadian behavior are associated with a decreased amplitude of mRNA expression of core-clock components in the periphery, as well as a delay in the phase of clock mRNA expression. When we housed rh3 flies under a 28 hour light:dark cycle (14h light:14h dark), the timing of their sleep and feeding was restored, and their lifespan was extended. Our future work aims to map the neuronal connections linking rh3-expressing photoreceptor cells and the core clock neurons in the brain, which set 24 hour locomotor rhythms. In conclusion, we have shown that rh3 is required for 24 hour circadian periodicity, which affects the daily timing of sleep and feeding. These results suggest that distinct populations of photoreceptor cells are required for maintaining circadian rhythms in Drosophila.

rhodopsin 3 regulates circadian periodicity