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Analysis of the Amphioxus Genome

  1. Noriyuki Satoh

Published Online: 15 SEP 2009

DOI: 10.1002/9780470015902.a0021556

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eLS

How to Cite

Satoh, N. 2009. Analysis of the Amphioxus Genome. eLS. .

Author Information

  1. Okinawa Institute of Science and Technology Promotion Corporation, Marine Genomics Unit, Uruma, Okinawa 904-2234, Japan

Publication History

  1. Published Online: 15 SEP 2009

Abstract

Amphioxus or cephalochordates are small fish-like marine invertebrates. The sequenced genome of Branchiostoma floridae is approximately 520 Mb in size and estimated to contain approximately 21 900 protein-coding loci. Comparison of the amphioxus genome with genomes of other animals made a great impact on the resolution of the long-standing question of the origin of vertebrates. First, chordates are monophyletic group, in which cephalochordates represent the most basal extant chordate lineage, with urochordates sister to vertebrates. Second, there is highly conserved synteny between the cephalochordate and vertebrate genomes. This allows reconstruction of 17 ancestral chordate linkage groups that are conserved in the modern amphioxus and vertebrate genomes. Third, the two rounds of genome-wide duplications occurred in the vertebrate lineage after their divergence from cephalochordates and urochordates. Fourth, whereas most duplicate genes have been lost, a disproportionate number of genes are retained and involved in developmental processes to produce novel features and complexity of vertebrate biology.

Key concepts

  • The phylum Chordata consists of the subphyla Cephalochordata (amphioxus), Urochordata (ascidians) and Vertebrata, and these three groups are characterized by possession of a notochord, a hollow dorsal neural tube, a perforated pharyngeal region and a post-anal tail.

  • Chordates are monophyletic group in which cephalochordates represent the most basal extant lineage, suggesting a free-living ancestor of chordates.

  • Seventeen ancestral chordate linkage groups that are conserved in the modern amphioxus and vertebrate genomes are revealed by highly conserved synteny between the two genomes.

  • The two rounds of genome-wide gene duplications occurred in the vertebrate lineage after their divergence from cephalochordates and urochordates.

  • A disproportionate number of genes which were produced by the genome-wide duplication are retained and involved in developmental processes to produce novel features and complexity of vertebrate biology.

Keywords:

  • amphioxus genome;
  • evolution of chordates;
  • origin of vertebrates;
  • ancestral chordate linkage groups;
  • two rounds of genome-wide gene duplications