Author:
Ryan Joseph F,Pang Kevin,Mullikin James C,Martindale Mark Q,Baxevanis Andreas D,
Abstract
Abstract
Background
The much-debated phylogenetic relationships of the five early branching metazoan lineages (Bilateria, Cnidaria, Ctenophora, Placozoa and Porifera) are of fundamental importance in piecing together events that occurred early in animal evolution. Comparisons of gene content between organismal lineages have been identified as a potentially useful methodology for phylogenetic reconstruction. However, these comparisons require complete genomes that, until now, did not exist for the ctenophore lineage. The homeobox superfamily of genes is particularly suited for these kinds of gene content comparisons, since it is large, diverse, and features a highly conserved domain.
Results
We have used a next-generation sequencing approach to generate a high-quality rough draft of the genome of the ctenophore Mnemiopsis leidyi and subsequently identified a set of 76 homeobox-containing genes from this draft. We phylogenetically categorized this set into established gene families and classes and then compared this set to the homeodomain repertoire of species from the other four early branching metazoan lineages. We have identified several important classes and subclasses of homeodomains that appear to be absent from Mnemiopsis and from the poriferan Amphimedon queenslandica. We have also determined that, based on lineage-specific paralog retention and average branch lengths, it is unlikely that these missing classes and subclasses are due to extensive gene loss or unusually high rates of evolution in Mnemiopsis.
Conclusions
This paper provides a first glimpse of the first sequenced ctenophore genome. We have characterized the full complement of Mnemiopsis homeodomains from this species and have compared them to species from other early branching lineages. Our results suggest that Porifera and Ctenophora were the first two extant lineages to diverge from the rest of animals. Based on this analysis, we also propose a new name - ParaHoxozoa - for the remaining group that includes Placozoa, Cnidaria and Bilateria.
Publisher
Springer Science and Business Media LLC
Subject
Developmental Biology,Genetics,Ecology, Evolution, Behavior and Systematics
Reference67 articles.
1. Pang K, Martindale MQ: Ctenophores. Curr Biol. 2008, 18: R1119-1120. 10.1016/j.cub.2008.10.004.
2. Cuvier G: Le Règne Animal Distribué Selon son Organisation, pour Servir de Base à l'Histoire Naturelle des Animaux et d'Introduction à l'Anatomie Comparée. 1817, Paris: Deterville
3. Leuckart R: Ueber die Morphologie und die Verwandtschaftsverhältnisse der wirbellosen thiere. Ein Beitrag zur Charakteristik und Classification der thierischen Formen. 1848, Braunschweig,: F. Vieweg und Sohn;
4. Harbison GR: On the classification and evolution of the Ctenophora. The Origins and Relationships of Lower Iinvertebrates. Edited by: Conway Morris S, George JD, Gibson R, Platt HM. 1985, London, UK: The Systematics Assocation, 28: 78-100.
5. Bridge D, Cunningham CW, DeSalle R, Buss LW: Class-level relationships in the phylum Cnidaria: molecular and morphological evidence. Mol Biol Evol. 1995, 12: 679-689.
Cited by
126 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献