Control of rhythmic output from the circadian clock in Neurospora crassa

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Title: Control of rhythmic output from the circadian clock in Neurospora crassa
Author: Lewis, Zachary Austin
Abstract: Circadian rhythms are visible as daily oscillations in biochemical , physiological , or behavioral processes . These rhythms are produced by an endogenous clock that maintains synchrony with the external environment through responses to external stimuli such as light or temperature . The clock , in turn , coordinates internal processes in a time -dependent fashion . Genetic and molecular analysis of the filamentous fungus Neurospora crassa has demonstrated that the products of the frequency (frq ) and white -collar (wc -1 and wc -2 ) genes interact to form an interlocked feedback loop that lies at the heart of the clock in this fungus . This feedback loop , termed the FRQ /WC oscillator , produces a ~24h oscillation in frq mRNA , FRQ protein , and WC -1 protein . In turn , the FRQ /WC oscillator regulates rhythmic behavior and gene expression . The goal of this dissertation is to understand how rhythmic outputs are regulated by the FRQ /WC oscillator in Neurospora . To this end , we have taken a microarray approach to first determine the extent of clock -controlled gene expression in Neurospora . Here , we show that circadian regulation of gene expression is widespread ; 145 genes , representing 20 % of the genes we analyzed , are clock -controlled . We show that clockregulation is complex ; clock -controlled genes peak at all phases of the circadian cycle . Furthermore , we demonstrate the clock regulates diverse biological processes , such as intermediary metabolism , translation , sexual development and asexual development . WC -1 is required for all light - and clock -regulated gene expression in Neurospora . We have shown that overexpression of WC -1 is sufficient to activate clock -controlled gene expression , but is not sufficient to induce all light -regulated genes in Neurospora . This result indicates that cycling of WC -1 is sufficient to regulate rhythmic expression of a subset of clockcontrolled genes . Conversely , a post -translational mechanism underlies WC -1 mediated light signal transduction in Neurospora . Finally , we have demonstrated the Neurospora circadian system is comprised of mutually coupled oscillators that interact to regulate output gene expression in the fungus .
URI: http : / /hdl .handle .net /1969 .1 /1376
Date: 2005-02-17

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Control of rhythmic output from the circadian clock in Neurospora crassa. Available electronically from http : / /hdl .handle .net /1969 .1 /1376 .

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