Evolution of the nucleus

Abstract

The nucleus represents a major evolutionary transition. As a consequence of separating translation from transcription many new functions arose, which likely contributed to the remarkable success of eukaryotic cells. Here we will consider what has recently emerged on the evolutionary histories of several key aspects of nuclear biology; the nuclear pore complex, the lamina, centrosomes and evidence for prokaryotic origins of relevant players.

Figure 1

Phylogenetic tree of the current view of the topology of life and eukaryota. (a) Relationship between prokaryotes and eukaryotes, assuming the three-domain model, whereby the Eukaryota emerged from the Archaea. An alternate two domain model, proposes that the Eukaryotes arose as a lineage within the Archaea, but this remains unresolved [85,86]. LECA/FECA; Last/first eukaryotic common ancestor. (b) Eukaryotic phylogeny, based on discussions provided in [87]. Some relationships, for example within the SAR + CCTH and Excavata clades remain to be fully resolved. Examples of commonly studied and/or organisms familiar to most experimental cell biologists are provided to anchor the reader, and supergroups are indicated by bars. There is a clear emphasis within many clades in the study of pathogenic species, for obvious and fully justified reasons. SAR + CCTH; Stramenopile, Alveolata, Rhizaria + Cryptophyta, Centrohelida, Telonemia and Haptophyta.

Figure 2

Important structures associated with the nuclear envelope. A sector of a generalised nucleus is shown, with various structures drawn as cartoons either embedded within the nuclear envelope or associated with it. Note that the structures are not drawn to an accurate scale.

Figure 3

A number of features associated with prokaryotic cells that are shared with eukaryotes. Note that not all of these features are present in any one lineage. Highlighted endomembrane complexes are putative protocoatomer-like proteins that may associate with membrane in the planctomycetes, bacterial dynamin that is associated with cytokinesis and possibly other membranous structures, the partial ESCRT system found in Archaea and which plays a conserved role in cytokinesis with eukaryotes. Archaea also possess histone-like proteins and a PCNA ortholog, while it is likely that the centrosome was associated with an early membranous structure that gave rise to the nuclear envelope.