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Biological Theory

, Volume 14, Issue 1, pp 30–41 | Cite as

The Nature of Programmed Cell Death

  • Pierre M. DurandEmail author
  • Grant Ramsey
Original Article

Abstract

In multicellular organisms, cells are frequently programmed to die. This makes good sense: cells that fail to, or are no longer playing important roles are eliminated. From the cell’s perspective, this also makes sense, since somatic cells in multicellular organisms require the cooperation of clonal relatives. In unicellular organisms, however, programmed cell death (PCD) poses a difficult and unresolved evolutionary problem. The empirical evidence for PCD in diverse microbial taxa has spurred debates about what precisely PCD means in the case of unicellular organisms (how it should be defined). In this article, we survey the concepts of PCD in the literature and the selective pressures associated with its evolution. We show that definitions of PCD have been almost entirely mechanistic and fail to separate questions concerning what PCD fundamentally is from questions about the kinds of mechanisms that realize PCD. We conclude that an evolutionary definition is best able to distinguish PCD from closely related phenomena. Specifically, we define “true” PCD as an adaptation for death triggered by abiotic or biotic environmental stresses. True PCD is thus not only an evolutionary product but must also have been a target of selection. Apparent PCD resulting from pleiotropy, genetic drift, or trade-offs is not true PCD. We call this “ersatz PCD.”

Keywords

Adaptation Aging Apoptosis Price equation Programmed cell death Selection Unicellular organisms 

Notes

Acknowledgements

PMD is supported by grants from the National Research Foundation (South Africa) and the Centre of Excellence for Palaeosciences. We thank Andrew Ndhlovu, Victor Luque, and two anonymous reviewers for helpful comments that improved this manuscript significantly.

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Copyright information

© Konrad Lorenz Institute for Evolution and Cognition Research 2018

Authors and Affiliations

  1. 1.Evolutionary Studies InstituteUniversity of the WitwatersrandJohannesburgSouth Africa
  2. 2.Institute of PhilosophyKU LeuvenLeuvenBelgium

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