Details

Autor(en) / Beteiligte

• Majercak, John Michael

Titel

The effects of light and temperature on the Drosophila circadian clock

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2001

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Circadian rhythms are driven by endogenous time keeping devices known as clocks. Circadian clocks are found in a wide range of organisms and act to align behavior and physiology to the solar day. An important feature of clocks is their ability to entrain to the environment through stimuli such as light and temperature. The circadian timing system can be described as having input pathways which carry information about the environment to an internal pacemaker or clock which in turn regulates overt behavior through output pathways. However, it is not clear how the circadian clock regulates downstream rhythms. Prior work suggested that cAMP has a role in the Drosophila circadian timing system. In this thesis, a cAMP specific protein kinase (PKA) was shown to regulate downstream rhythms in select circadian behavior without disrupting clock function. In addition, this thesis describes the first study of how the phase of a circadian clock is coregulated by temperature and photoperiod. We show that splicing of the 3′-terminal intron of period (per) RNA is affected by temperature and light such that at cold temperatures and short photoperiods the relative ratio of the spliced transcript is increased, leading to an earlier rise in the upswing of per mRNA. Long photoperiods partially counteract cold-induced phase advances in the accumulation phase per mRNA and protein by delaying the upswing in the photosensitive TIMELESS (TIM) protein. The functional interrelationships between PER and TIM ensure that information concerning temperature and light is properly integrated leading to activity rhythms that are optimally aligned with the prevailing environmental conditions. Furthermore, we have identified a novel effect of light on the splicing of the 3′-terminal intron of per RNA. The work described in this thesis leads us to a better understanding of how seasonal differences in ambient temperature and day-length affect behavioral rhythms.