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. 2023 Feb 14;120(7):e2221818120.
doi: 10.1073/pnas.2221818120. Epub 2023 Feb 10.

How ciliates got their nuclei

Vittorio Boscaro  1 , Patrick J Keeling  1
Affiliations

How ciliates got their nuclei

Vittorio Boscaro et al. Proc Natl Acad Sci U S A. .
No abstract available

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Conflict of interest statement

The authors declare no competing interest.

Figures

Fig. 1.
Fig. 1.
Hypothesis for the evolution of ciliate nuclear dimorphism and IES spread (see text for details). (A) An ancient ancestor of ciliates would have been uninucleate. (B) Selection for increased cell size and the increased gene expression this requires was initially accommodated by maintaining multiple nuclei. (C) Subsequently, one nucleus specialized, becoming an enlarged “proto-macronucleus” with expanded chromosome numbers, but which cannot undergo mitosis or meiosis and cannot divide. (D) The remaining “proto-micronucleus” continues to undergo mitosis and meiosis, but is no longer required for gene expression, and eventually neutrally falls silent. (E–F) This functional specialization allows a runaway spread and inheritance of transposons (now referred to as IESs) in micronucleus because they are eliminated in the developing macronucleus by a domesticated transposase. All these steps occurred before the last common ancestor of ciliates. Subsequently two lineages independently evolved an imprecise amitotic division of the macronucleus, but no macronucleus can undergo meiosis, and the germline micronucleus is still required to reset the macronucleus during each sexual exchange.
See this image and copyright information in PMC

Comment on

  • doi: 10.1073/pnas.2213985120
  • doi: 10.1073/pnas.2213887120

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