Plant Biol (Stuttg) 2005; 7(5): 425-448
DOI: 10.1055/s-2005-865899
Review Article

Georg Thieme Verlag Stuttgart KG · New York

Asymmetric Cell Divisions in Flowering Plants - One Mother, “Two-Many” Daughters

R. M. Ranganath1
  • 1Cytogenetics and Developmental Biology Laboratory, Department of Botany, Bangalore University - 560056, India
Further Information

Publication History

Received: June 8, 2004

Accepted: May 6, 2005

Publication Date:
15 September 2005 (online)

Abstract

Plant development shows a fascinating range of asymmetric cell divisions. Over the years, however, cellular differentiation has been interpreted mostly in terms of a mother cell dividing mitotically to produce two daughter cells of different fates. This popular view has masked the significance of an entirely different cell fate specification pathway, where the mother cell first becomes a coenocyte and then cellularizes to simultaneously produce more than two specialized daughter cells. The “one mother - two different daughters” pathways rely on spindle-assisted mechanisms, such as translocation of the nucleus/spindle to a specific cellular site and orientation of the spindle, which are coordinated with cell-specific allocation of cell fate determinants and cytokinesis. By contrast, during “coenocyte-cellularization” pathways, the spindle-assisted mechanisms are irrelevant since cell fate specification emerges only after the nuclear divisions are complete, and the number of specialized daughter cells produced depends on the developmental context. The key events, such as the formation of a coenocyte and migration of the nuclei to specific cellular locations, are coordinated with cellularization by unique types of cell wall formation. Both one mother - two different daughters and the coenocyte-cellularization pathways are used by higher plants in precise spatial and time windows during development. In both the pathways, epigenetic regulation of gene expression is crucial not only for cell fate specification but also for its maintenance through cell lineage. In this review, the focus is on the coenocyte-cellularization pathways in the context of our current understanding of the asymmetric cell divisions. Instances where cell differentiation does not involve an asymmetric division are also discussed to provide a comprehensive account of cell differentiation.

References

R. M. Ranganath

Department of Botany
Bangalore University
Jnanabharathi Campus

Bangalore 560056

India

Email: rayasran@rediffmail.com

Editor: J. Raven

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