Circadian Expression of PERIOD and the Pigment-Dispersing Factor in the yellow white mutant Drosophila melanogaster

Abstract

Daily behavioral andphysiological rhythms in most animals are regulated by a circadian clock. Inthe fruit fly, Drosophila melanogaster, this clock consists of a networkof about 150 cerebral neurons. Different parameters of the fruit fly circadianlocomotion are attributed to specific neuronal subsets and the molecularrhythms of clock genes and proteins within them. To understand the clockmachinery, many clock mutant flies have been used. yellow white (y w) mutation in D. melanogaster cause impairedmelanisation, eye pigmentation loss, and behavioral alterations includingchanges in circadian locomotion. This study investigates the possible molecularbackground for these circadian alterations. Results revealed that in the outputpathway of the clock, the Pigment-Dispersing Factor (PDF) expression wassuppressed in y w mutant fruit flies compared to Canton S (CS) wild-type in the PDF+ clock neurons. Onthe other hand, the degradation of the PERIOD (PER) protein was significantlydelayed in yw mutants and their levels was higher, especially atthe transition from dark to light. The combined effect of elevated PER levelsand suppressed PDF signaling provides an explanation for the delayed morninglocomotor activity peak (M) and advanced evening peak (E) of y w fliescompared to CS.It could be concluded that mutations affecting eye pigmentation like the y w mutationcould have profound effects on the circadian regulation of behavior and theirunderlying molecular oscillations in clock neurons. These effects reduce theplasticity and robustness of the circadian clock and expose the flies to higherlevels of the environmental risk of desiccation.