Student Theses and Dissertations

Date of Award

2006

Document Type

Thesis

RU Laboratory

Young M Laboratory

Keywords

circadian clocks, circadian clocks--role of temperature, circadian gene expression, drosophila melanogaster, drosophila clock

Abstract

Clocks are aligned to the environment via inputs from both daily light and temperature cycles. Previous molecular and behavioral studies in Drosophila have largely focused on light-dependent regulation of circadian clocks and their outputs. Although light is the strongest and best understood Zeitgeber for the circadian clock, temperature is also an important factor. This thesis aims to understand better the role of temperature on gene expression and behavior in the fly, as well as to examine how information from both light and temperature are integrated by the clock to regulate circadian gene expression. Genome-wide expression profiles of transcripts from wild-type, lightentrained flies show a similar transcriptional response in entrainment and free-run. In contrast, expression profiles from wild-type, temperatureentrained flies show a dramatic difference in the presence or absence of a thermocycle. Whereas almost all transcription appears to be modified by changes in temperature, there is a limited number of transcripts that continue to oscillate in constant conditions following temperature entrainment. This suggests two distinct responses to temperature: clock-independent temperature-driven oscillations and clock-dependent circadian oscillations. The clock-dependent transcripts oscillating in constant conditions following temperature entrainment show a significant overlap with those transcripts oscillating in response to photocycles. Further, they maintain the same mutual phase relationships after entrainment by temperature or light. That is, the phase observed at the onset of the thermophase is systematically advanced by about six hours relative to the phase at the onset of light. A similar phase relationship is observed at the level of protein expression and locomotor activity behavior. These observations indicate that entrainment by light and temperature would occur cooperatively and be integrated by the fly under natural circumstances, given the size of the delay that is commonly found between environmental temperature profiles and light/dark cycles.

Comments

A thesis presented to the faculty of The Rockefeller University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

Permanent URL

http://hdl.handle.net/10209/224

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