Circadian regulation of the bimodal rhythm of cyclic AMP
in wildtype Euglena
Edmunds, L.N., Jr. and Mohabir, G.
Division of Biological Sciences, State University of New York, Stony Brook,
New York 11794, USA
We have shown earlier that cell-cycle traverse is associated with fluctuations in the cellular content of cAMP and that artificial alterations of those levels, in fact, do phase-shift cell division in free-running cultures of achlorophyllous Euglena. The phase shifts, however, were only transient: the cell division rhythm rephased to that of unperturbed controls. This implies that the second messenger functions downstream of the circadian oscillator. Further, the level of cAMP is known to reflect carbon nutrient status and the competency of cells to traverse various restriction points in the cell cycle of other eukaryotes. We wished to determine the profile of cAMP content in free-running, dividing and nondividing cultures of green, wild-type cells, which survive well during prolonged growth arrest. We monitored cAMP content in photoautotrophic cultures of the algal flagellate E. gracilis (strain Z) under either entraining (LD: 12,12) or free-running (LD: ½, ½,) regimes at 25 oC. Cyclic AMP content in both rhythmically dividing, light-phased and free-running cells exhibited bimodality (peaks at CT 9-14, CT 19-22). Expression of cAMP content on a per mg total cellular protein basis caused the day trough (CT 1-3) to be even more distinct. Nondividing, free-running cultures displayed a similarly phased bimodality in cAMP content. These findings in wild-type Euglena confirm that the bimodal rhythm of cAMP content is regulated by the circadian oscillator and is not dependent on the cell division cycle.
| LOCATION |
DATE |
TIME |
| Lecture Hall II |
Thursday, April 9 |
02:20 pm |