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Analysis of light/dark synchronization of cell-wall-less Chlamydomonas reinhardtii (Chlorophyta) cells by flow cytometry

Published online by Cambridge University Press:  01 August 1999

STEPHANE D. LEMAIRE
Affiliation:
Institut de Biotechnologie des Plantes, UMR 8618 CNRS, Université Paris-Sud, Bâtiment 630, 91405 Orsay Cedex, France
MICHEL HOURS
Affiliation:
Institut de Biotechnologie des Plantes, UMR 8618 CNRS, Université Paris-Sud, Bâtiment 630, 91405 Orsay Cedex, France
CATHERINE GERARD-HIRNE
Affiliation:
Institut de Biotechnologie des Plantes, UMR 8618 CNRS, Université Paris-Sud, Bâtiment 630, 91405 Orsay Cedex, France
ANNE TROUABAL
Affiliation:
Institut de Biotechnologie des Plantes, UMR 8618 CNRS, Université Paris-Sud, Bâtiment 630, 91405 Orsay Cedex, France
ODILE ROCHE
Affiliation:
Institut de Biotechnologie des Plantes, UMR 8618 CNRS, Université Paris-Sud, Bâtiment 630, 91405 Orsay Cedex, France
JEAN-PIERRE JACQUOT
Affiliation:
Institut de Biotechnologie des Plantes, UMR 8618 CNRS, Université Paris-Sud, Bâtiment 630, 91405 Orsay Cedex, France
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Abstract

The degree of synchrony of light/dark-adapted Chlamydomonas reinhardtii cell-wall-less cells was analysed by flow cytometry. The cultures exhibited the classical growth curve reported for synchronously dividing cells. However, analysis of the nuclear DNA content revealed a partial asynchrony of cell division. This allowed us to determine that cell division lasts only 1 h 15 min. The changes in the distribution of nuclei in G1 and S phases did not exhibit the DNA peaks expected for highly synchronous cells. However, these peaks were observed for the G2+M nuclei and reflected the number of cell divisions. Modification of culture conditions including temperature, photoperiod, quantum irradiance and culture density affected the degree of synchrony but did not completely abolish the asynchrony. An overlap between the divisions of cells dividing one, two or three times could account for the partial asynchrony observed. In fact, it is possible that cells perform their divisions synchronously but that the timing and/or the duration of the cell divisions is different for the three kinds of cells. The synchrony seems to be perturbed when the cells move from the G1 to the S phase. The transduction of the release signal, allowing cells to pass through the restriction point of the G1 phase, might be too slow and insufficiently homogeneous between the cells to allow perfect synchronization. Finally, if highly synchronized cells are needed to study Chlamydomonas reinhardtii cell cycle, other synchronization procedures should be considered.

Type
Research Article
Copyright
© 1999 British Phycological Society

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