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. 2015 Aug 18;112(33):10120-5.
doi: 10.1073/pnas.1421378112. Epub 2015 Apr 14.

Reproduction, symbiosis, and the eukaryotic cell

Peter Godfrey-Smith  1
Affiliations

Reproduction, symbiosis, and the eukaryotic cell

Peter Godfrey-Smith. Proc Natl Acad Sci U S A. .

Abstract

This paper develops a conceptual framework for addressing questions about reproduction, individuality, and the units of selection in symbiotic associations, with special attention to the origin of the eukaryotic cell. Three kinds of reproduction are distinguished, and a possible evolutionary sequence giving rise to a mitochondrion-containing eukaryotic cell from an endosymbiotic partnership is analyzed as a series of transitions between each of the three forms of reproduction. The sequence of changes seen in this "egalitarian" evolutionary transition is compared with those that apply in "fraternal" transitions, such as the evolution of multicellularity in animals.

Keywords: eukaryote; evolution; reproduction; symbiosis.

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Conflict of interest statement

The author declares no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Some distinctions central to this paper. Recurring structures may either be reproducing or reconstructed. Reproducing objects form parent–offspring lineages, whereas reconstructed ones do not. Reconstructed objects in this sense include enzymes, organs, and ribosomes (pictured). Reproduction may be collective, simple, or scaffolded. Collective reproducers include multicellular organisms. An example of a simple reproducer is a prokaryotic cell. Scaffolded reproducers, which rely on external machinery for their reproduction, include genes and viruses. A collective reproducer may contain any of the other kinds of reproducer. A simple reproducer may only contain scaffolded reproducers, such as genes. A scaffolded reproducer also may contain other scaffolded reproducers.
Fig. 2.
Fig. 2.
A breakdown of evolutionary transitions involving endosymbiosis, featuring movement between three kinds of reproduction. A system starts with two simple reproducers. One engulfs the other, yielding a collective reproducer, but initially the collective reproducer is unified only by physical containment. The collective reproducer becomes more metabolically integrated, and eventually, through gene loss, the endosymbiont moves toward scaffolded reproduction.
See this image and copyright information in PMC

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