Analysis of circadian locomotor rhythms in vg and cry^b mutants of Drosophila melanogaster under different light: dark regimens

Abstract

The fruit fly (Drosophila melanogaster) offers an extremely useful system to study circadian clock function at the behavioral, molecular, cellular, and organismal levels. We reared wild type (Oregon R⁺) and mutant flies – vestigial (vg) and cryptochrome depleted (cry^b ) flies in 12:12 light:dark cycles (LD 12:12) from the embryo to adult stage. Later, the locomotor activity rhythms of these newly eclosed flies were monitored in different light:dark (LD) regimens such as T20 (LD 10:10), T22 (LD 11:11), T24 (LD 12:12), T26 (LD 13:13), T28 (LD 14:14), continuous light (LL), and continuous darkness (DD) for seven to eight cycles. The circadian locomotor characteristics, such as period length, percentage activity, day and nighttime activity, anticipation index (AI), and phase relationships, were analyzed. Under these LD regimens, the above-mentioned characteristics were altered in these mutants when compared to wild-type (WT) flies. Altered circadian locomotor rhythms in vg mutants under these LD regimens might be due to its reduced wing structure. cry^b flies have defective photic input to clock and it showed altered circadian locomotor activity rhythms when compared to WT flies under all these LD regimens. From this study, we suggest that under different LD regimens blue-light component cryptochrome as well as wing structure play an important role for the expression of circadian locomotor rhythms in D. melanogaster.