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.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/1376 |
| Date | 17 February 2005 |
| Creators | Lewis, Zachary Austin |
| Contributors | Bell-Pedersen, Deborah |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 4983661 bytes, electronic, application/pdf, born digital |
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