Cyanobacteria contain a circadian oscillator
whose evolutionary origins are roughly 2 billion
years in the past which tracks the 24 hour day/night
cycle of the external environment. When cyanobacteria
are put in constant light conditions, however,
the clock continues to run independently for
many days with nearly the same period. Unlike
the circadian
oscillators in mammals and Drosophila,
which rely on gene repression and activation,
cyanobacterial oscillations continue in the absence
of transcription
and translation. In fact, as recently shown by
the Kondo lab, this oscillator can be spontaneously
reconstituted in vitro
using three purified clock proteins: KaiA, KaiB
and
KaiC.
I am interested in constructing and testing
models that can explain the observed features
of this
oscillator including its insensitivity to temperature
and its resistance to stochastic noise. This
search should illuminate general design principles
that
can be used to construct biological oscillators
using only post-translational modification
of proteins. Once the core of the oscillating
reaction is well
understood, I hope to unravel how synchronization
of both the phase and period of the clock with
external light conditions is achieved.
An improved understanding of the mechanistics
of the cyanobacterial
clock should also help to answer the underlying
evolutionary question: what fitness advantages
are to be gained by maintaining a free-running
clock rather than sensing ambient light levels
directly?
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