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Fifteen Years of Evolutionary Genomics in Caenorhabditis elegans

  1. Richard Jovelin,
  2. Alivia Dey,
  3. Asher D Cutter

Published Online: 15 MAY 2013

DOI: 10.1002/9780470015902.a0022897

eLS

eLS

How to Cite

Jovelin, R., Dey, A. and Cutter, A. D. 2013. Fifteen Years of Evolutionary Genomics in Caenorhabditis elegans. eLS. .

Author Information

  1. University of Toronto, Toronto, Ontario, Canada

Publication History

  1. Published Online: 15 MAY 2013

Abstract

The nematode worm Caenorhabditis elegans, introduced by Sydney Brenner for the genetic analysis of nervous system formation, is now a powerful model organism for studying nearly all aspects of biology, from development to diseases to evolution. Sequencing and analysis of the worm genome revealed intriguing nonrandom patterns of genome organisation and unusual features such as abundant operons. Surprising upon first discovery, worms and humans have a similar number of genes that are comprised of a similar proportion of transcription factors to regulate their genomes. However, differences in small ribonucleic acid content may contribute to differences in organismal complexity. In nature, the bacterivorous C. elegans is found primarily on rotting vegetation in temperate regions across the world. Natural selection, combined with the low effective recombination rate associated with selfing, strongly reduces nucleotide variation across the genome, yielding similarly low polymorphism to other selfing hermaphrodite species of Caenorhabditis. The genus Caenorhabditis provides a superb model system for ecological and evolutionary genetics, benefiting from C. elegans tools and information when applied to investigations of species with a higher polymorphism and better known ecological context.

Key Concepts:

  • The nematode Caenorhabditis elegans, introduced by Sydney Brenner for the genetic analysis of nervous system development, was the first metazoan to have a complete sequenced genome and is now a model organism for nearly all fields of biology.

  • Many genomic features are not randomly distributed along C. elegans chromosomes and are prevalent either in the chromosome arms or in its centre.

  • An unusually large fraction of protein-coding genes is organised in operons, possibly optimising transcriptional resources during recovery from developmental arrest.

  • Gene duplication and alternative splicing contribute to extensive diversification of gene function, with 10.5% of protein-coding genes having paralogs and 25% of genes being alternatively spliced.

  • The ratio of transcription factors to protein-coding genes is similar in worms and humans but the two species differ greatly in their microRNA content.

  • The differences in chromatin states contribute to phenotypic variation and the transgenerational epigenetic inheritance suggests a role for epigenetic information in evolution.

  • The rate of duplication is two orders of magnitude greater than the nucleotide mutation rate, highlighting the role of gene duplication in the evolution of the C. elegans genome.

  • Caenorhabditis is not a soil nematode but instead proliferates and feeds on bacteria in rotting vegetation.

  • Population genetic variation is strongly affected by the mating system of Caenorhabditis, with very low polymorphism in selfing hermaphroditic species relative to outcrossing gonochoristic species.

Keywords:

  • Caenorhabditis;
  • genome evolution;
  • operons;
  • gene regulation;
  • mating systems;
  • epigenetics;
  • polymorphism