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Myosin domain evolution and the primary divergence of eukaryotes
Thomas A Richards1, Thomas Cavalier-Smith
1Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. thomr@nhm.ac.uk
Nature
|August 27, 2005
Summary
Eukaryotic cells exhibit distinct cytoskeletal and ciliary structures, with myosin molecular motors reflecting this fundamental dichotomy. Comparative genomics reveals five key myosin innovations supporting the primary divergence of unikonts and bikonts.
Area of Science:
- Cell Biology
- Evolutionary Biology
- Genomics
Background:
- Eukaryotic cells display two primary cytoskeletal and ciliary organizations: the simpler unikont (single cilium) and the more complex bikont (ancestral bicilia).
- This cellular dichotomy suggests deep evolutionary divergence within eukaryotes.
Purpose of the Study:
- To investigate if myosin molecular motors also reflect the fundamental bikont/unikont cellular dichotomy.
- To identify and characterize myosin domain combinations across eukaryotic lineages.
Main Methods:
- Comparative genomic analysis of myosin protein domains.
- Phylogenetic analysis of sequence data.
- Examination of taxonomic distribution of myosin domain combinations.
Main Results:
- Discovery of 37 distinct myosin protein domain combinations, including novel ones.
- Identification of five key myosin innovations.
- Evidence supporting unikont monophyly and the primary bikont/unikont bifurcation based on myosin evolution.
Conclusions:
- The fundamental cellular dichotomy in eukaryotes is mirrored by distinct myosin molecular motor organizations.
- The eukaryotic cenancestor possessed a cilium, mitochondria, pseudopodia, and three contrasting myosin domain combinations.
- Myosin evolution provides strong support for the primary divergence of bikont and unikont lineages.
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