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Center for Molecular and Comparative Endocrinology and Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH, USAFig. 2. A diagram representing the evolution of GnRH in metazoans (A) and chordates (B). (A) Distinct GnRH lineages have been identified in metazoans including GnRH inTunicates; Mollusks and Annelids; and Vertebrates. From the information to date on the identification of the GnRHs there is likely an ancestral GnRH that gave rise to theGnRH lineages in the deuterostome and proteomes. (B) In the vertebrates and likely due to a genome/gene duplication event, an ancestral gene gave rise to two lineages ofGnRHs—the gnathostome GnRH and lamprey GnRH-II. The gene duplication events that generated the different fish and tetrapod paralogous groups likely took place withinthe Gnathostome lineage, after its divergence from the ancestral agnathans. Lamprey GnRH-I and III (type 4) can be identified now as paralogous homologs of GnathostomeGnRH and lamprey GnRH-II group, resulting from a duplication within the lamprey lineage. This implies that there probably was a genome/gene duplication event that gaverise to all forms of vertebrate GnRH affecting the common ancestor of lamprey and Gnathostome isoforms. The Gnathostome branch of the lamprey GnRH-I and -IIIorthologous group was probably lost during evolution. Distinct GnRH lineages are depicted as follows: tunicates (purple circle); mollusks and annelids, Type 5 GnRH, (orangecircle); mammalian GnRH and orthologs, Type 1 GnRH (brown circle); chicken GnRH-II and lamprey GnRH-II, Type 2 GnRH (green circle); salmon GnRH, Type 3 GnRH (lightblue circle); and lamprey GnRH-I and -III, Type 4 GnRH (dark blue circle). 1R, 2R and 3R indicate whole genome duplications. Phylogenetic diagram was modified from http://tolweb.org/Bilateria/2459/2002.01.01 in The Tree of Life Web Project, http://tolweb.org/.0016-6480/$ - see front matter 2009 Elsevier Inc. All rights reserved.doi:10.1016/j.ygcen.2009.04.019DOI of original article: 10.1016/j.ygcen.2008.11.023.* Corresponding author. Fax: +1 603 862 4013.E-mail address: sasower@cisunix.unh.edu (S.A. Sower). |
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