Journal of Cell Science, Vol 100, Issue 2 365-369, Copyright © 1991 by Company of Biologists

JOURNAL ARTICLES

Circadian rhythmicity in the activities of adenylate cyclase and phosphodiesterase in synchronously dividing and stationary-phase cultures of the achlorophyllous ZC mutant of Euglena gracilis

J Tong, IA Carre and LN Edmunds
Department of Anatomical Sciences, State University of New York, Stony Brook 11794.

Key factors in the adenosine 3',5'-cyclic monophosphate (cyclic AMP) metabolic pathway are two enzymes responsible for its generation and degradation, namely, adenylate cyclase (AC) and phosphodiesterase (PDE). In LD: 12,12 (12 h light, 12 h dark), these enzymes were found to undergo bimodal, circadian variation of activity in both dividing and nondividing cultures of the photosynthesis-deficient, achlorophyllous ZC mutant of Euglena gracilis Klebs (Z). Maximal AC activity occurred 2 h after the onset of the light interval (CT 02) and at the beginning of darkness (CT 12-14); these times corresponded to the acrophase profile for the rhythmic changes in cyclic AMP content that have been previously reported. The activity of PDE also exhibited a daily oscillation, but with an inverse phase pattern. Both the AC and PDE activity rhythms persisted after the cultures were transferred from LD: 12,12 to constant darkness. The activity of AC was activated significantly in vivo by forskolin at the trough phase (CT 20), while that of PDE was inhibited by 3-isobutyl-1-methyl-xanthine (IBMX) at its peak phase. These results indicate that the rhythms of both AC and PDE may be the main factors generating the circadian oscillations of cyclic AMP content in Euglena, which appear to be under control of an endogenous pacemaker.

This article has been cited by other articles:

				I. Carre and L. Edmunds Oscillator control of cell division in Euglena: cyclic AMP oscillations mediate the phasing of the cell division cycle by the circadian clock J. Cell Sci., January 4, 1993; 104(4): 1163 - 1173. [Abstract] [PDF]