Reciprocal Behaviour Associated with Altered Homeostasis and Photosensitivity of Drosophila Clock Mutants

Abstract

The circadian oscillators of genetically short-period and long-period Drosophila exhibit reciprocal behaviour in four distinct ways: (1) with respect to the dependence of period on temperature, (2) in the change of period during constant darkness after ten days of constant light, (3) in the change of period during the second ten days of darkness as compared with the period during the first ten days, and (4) in the period change resulting from exposure to low-intensity constant light. The homeostatic control of the dependence of period length on temperature is impaired in the mutants as compared with wild-type flies. The normal Drosophila pacemaker may comprise two mutually coupled oscillators, whereas the mutants may represent a reduction in activity of one or the other constituent oscillator.

Rhythm Defects Caused by Newly Engineered Null Mutations in Drosophila's cryptochrome Gene

“…That one of them includes photoreception by CRY in the head was signified by two further tests (Stanewsky et al 1998;Emery et al 2000a): (i) cry b individuals were found not to exhibit locomotor phase shifts after relatively brief light pulses were delivered to flies otherwise maintained in constant darkness (DD) and (ii) cry b behaved in an anomalously rhythmic manner in LL. Genetically normal Drosophila behave arrhythmically when the LL intensity is rather high but exhibit longer than normal (compared with DD) locomotor periods in dim light (Konopka et al 1989). By comparison, cry b individuals have been reported either to display periodicities in LL that are either equivalent to the free-running behavior of wild-type Drosophila in DD (Emery et al 2000a) or entail slightly lengthened cycle durations MealeyFerrara et al 2003).…”

Functional Analysis of Circadian Pacemaker Neurons inDrosophila melanogaster

“…The model also predicts that the M oscillator will free-run with short period and the E oscillator with long period when animals are placed in constant light. However, such internal desynchronization between oscillators does not occur, because high-intensity constant light usually results in arrhythmicity (Aschoff, 1979;Konopka et al, 1989). In D. melanogaster, the clock protein Timeless (TIM) is permanently degraded during light-induced interaction with Cryptochrome (CRY), leading finally to the arrest of the clock (Ceriani et al, 1999;Emery et al, 2000;Rosato et al, 2001;Busza et al, 2004).…”

Synchronization of theDrosophilaCircadian Clock by Temperature Cycles

“…This dependency was only observable in LL; in DD, wild-type flies synchronized to T = 24 but not to any of the other T cycles (Yoshii et al 2002). The findings suggest "better clock function" in LL compared to DD during temperature entrainment, which is quite surprising given that LL causes arrhythmicity at constant temperatures (Konopka et al 1989; also see below).…”

“…In LL and constant temperatures, molecular and behavioral rhythmicity breaks down (Konopka et al 1989;Marrus et al 1996), presumably because of the lightinduced and Cry-mediated degradation of Tim (see, e.g., Stanewsky et al 1998;Ceriani et al 1999;Busza et al 2004). Nevertheless, robust behavioral synchronization and oscillations of per and tim gene products are observed in LL and temperature cycles (Glaser and Stanewsky 2005;Matsumoto et al 1998;Miyasako et al 2007;Yoshii et al 2002Yoshii et al , 2005.…”

“…Cry has also been implicated in temperature compensation, because a mutant form of Cry, encoded by the cry b mutation, largely restores the deficit of compensation associated with a mutation in the clock gene period (per L ) (Konopka et al 1989;Kaushik et al 2007). It is not clear whether this "rescue" is only a consequence of altered binding properties between the clock protein Timeless (Tim) and the mutated and perhaps structurally altered Cry B and Per L proteins.…”