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Programmed Nuclear Death and Other Apoptotic-Like Phenomena in Ciliated Protozoa

  • Ana Martín González
  • Silvia Díaz
  • Andrea Gallego
  • Juan C. Gutiérrez
Part of the Molecular Biology Intelligence Unit book series (MBIU)

Abstract

One of the more usual hallmarks of programmed cell death (PCD) in multicellular organisms is the nuclear chromatin condensation and the DNA fragmentation in multiple oligonucleosome length fragments. In Tetrahymena thermophila and other free-living ciliated protozoa, a controlled nuclear degradation process develops during conjugation, the sexual phase of the life cycle, which includes DNA condensation and later degradation, with or without previous nuclear fragmentation. The main objective of this programmed nuclear death (PND) is to remove the old macronucleus whereas a new recombinant vegetative nucleus is developing in each conjugating cell. Alternatively, in other ciliates, mainly inhabitants of terrestrial ecosystems, which have not conjugation, PND is restricted to encystment, a cellular differentiation process induced by different environmental stressors, mainly starvation, the same inducer of conjugation. The mechanism of PND is still not elucidated, but we know that it involves caspase-like proteins, an intense acid phosphatase activity and an autophagic process. Also, several reports indicate the existence of mitochondrial participation in macronuclear degradation. After analysing the updated information relative to programmed nuclear death in ciliated protozoa, we conclude that these eukaryotic microorganisms represent an alternative and good option to study the PCD process in unicellular organisms. The recently completed macronuclear genome sequencing in the model ciliate T. thermophila, provides insights to analyze and understand the molecular mechanisms of PCD in ciliates and, likewise, it will give rise to useful information about the origin and evolution of cell death in biological systems.

Keywords

Chromatin Condensation Cell Death Differ Ciliated Protozoan Eukaryotic Microorganism Zygotic Nucleus 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Landes Bioscience and Springer Science+Business Media 2008

Authors and Affiliations

  • Ana Martín González
    • 1
  • Silvia Díaz
    • 1
  • Andrea Gallego
    • 1
  • Juan C. Gutiérrez
    • 1
  1. 1.Departamento de Microbiología-III, Facultad de BiologíaUniversidad Complutense (UCM)MadridSpain

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