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Chapter category: Circadian Rhythms
Biochemistry and Circadian Regulation of Output from the Gonyaulax Clock: Are There Many Clocks or Simply Many Hands?
Chapter authors:
Nasha Nassoury, J. Woodland Hastings and David Morse
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The unicellular dinoflagellate Gonyaulax exhibits numerous circadian-controlled
processes, many of which are amenable to study and biochemical analysis. Their peaks
(acrophases) fall roughly into three classes. Bioluminescence flashing and the abundance
of proteins involved in bioluminescence are greatest in the middle of the night phase; cell
division and a bioluminescent glow occur around the transition from night to day phase; while
motility and photosynthesis peak during the day phase, along with the synthesis of proteins
associated with photosynthesis. Although these several rhythms are typically in synchrony,
exhibiting the same free-running periods and other properties, there are conditions under which
they can dissociate and exhibit different periods. Biochemical correlates of several rhythms
have been identified and, for some, circadian changes in the rates of synthesis of several proteins
have been shown to be associated with the rhythms. In each of the cases studied, the
circadian regulation of protein synthesis has been found to be controlled at a translational level,
rather than by the abundance of the relevant mRNAs.
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