Molecular genetics of a circadian clock in Drosophila melanogaster--- : the relationship between environmetal/developmental factors, period (per) gene expression and behavioral rhythmicity /
The period (per) gene is thought to be an integral component
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1996.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739363591&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The period (per) gene is thought to be an integral component of the Drosophila circadian pacemaker. Circadian fluctuations in per MRNA and protein levels are central to the operation of a negative feedback loop which is necessary for setting the free-running period, for entraining the circadian oscillator to light-dark cycles, and for controlling various rhythmic outputs such as locomotor activity and eclosion. Environmental and developmental factors interact with per-dependent oscillators either directly or indirectly to determine the phase or timing of the behavioral outputs. The effects of environmental light- dark cycles on per MRNA cycling and per feedback loop function have been examined in the first part of this study. These results suggest that the per feedback loop uses lights- off as a phase reference point, that a minimum dark phase is required for per feedback loop function, and that an additional (non-PER) activator or repressor is operating in the per feedback loop. In the second part of this study, a behavioral approach has been used to examine the interaction between developmental state and the circadian clock in determining the timing of eclosion. At a certain phase of the circadian cycle the circadian clock measures developmental state, and those pharate adults that have reached a certain developmental state by this phase eclose during the first available gate, while those that have not wait until a subsequent gate. These experiments indicate that the circadian clock measures developmental state (wing pigmentation) in wild type flies between lightsoff and expression of the first clock regulated marker -4-5hr before eclosion, and that the developmental state of the fly determines both which gate is chosen for eclosion and when eclosion occurs during that gate. For the final part of this study, per upstream cycling enhancer fragment driven per expression was used to study the relationship between the per expression and behavioral rhythmicity. The abundance of per protein from these transgenic per 01 lines in which per gene expression is driven by the circadian enhancer containing cis sequences (-1313 to -34 and -603 to -156) fluctuates in light-dark cycling conditions (LD) with high levels late in the dark phase and low to undetectable levels late in the light phase. The overall abundance of per MRNA derived from the transgene is relatively higher than that of per MRNA in wild type flies and the endogenous per 01 MRNA. The levels of per MRNA from both the transgene and the endogenous pero I MRNA cycle with similar amplitude as those in wild type flies, but the peak levels are 4-8 hours earlier than that of the wild type flies in LD conditions. These per MRNA fluctuations continue in constant darkness, but with lower amplitudes. The transformants anticipate the light - dark transition by becoming more active in LD conditions, and a small proportion of the transformants are rhythmic in locomotor activity in constant darkness. These results indicate the overall level, cycling amplitude, and cycling phase of per gene expression are important parameters which dictate the extent of behavioral rescue of per 0l mutants. |
|---|---|
| Item Description: | Vita. "Major Subject: Biology". |
| Physical Description: | xi, 127 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 118-124. |