Amphioxus takes center stage as genome sequenced
The chordates contain invertebrate groups (amphioxus and tunicates) and vertebrate groups (the jawless vertebrates, such as the lamprey,and the jawed vertebrates).Amphioxus holds on to the last branch of the tree of chordates,closest non chordate relatives being hemichordates and echinoderms.Lancelets, or amphioxus, are marine animals resemble a worm which spend most of their lives buried in the sea floor, feeds through jawless, ciliated mouths.One will be forgiven for not being heard of Amphioxus ,an organism lacking a distinct head and possess notochord(Alexander Kowalevsky recognized the chordate affinities of this organism) that form defining feature of chordates.Amphioxus is not widely known to the general public, but is gaining interest in scientific community as it is one of the closest living invertebrate relatives of vertebrates. Although amphioxus split from vertebrates more than 520 million years ago, its genome holds tantalizing clues about evolution.
Nicholas H. Putnam and colleagues published ~520-megabase draft genome sequence of Branchiostoma floridae, one of the 25 or so recognized species of Amphioxus.This might get Amphioxus to center stage of Evolutionary biology and back into public life.The draft genome reveals its basal identity among chordates and also displays strong synetny (In comparative genomics, synteny describes the preserved order of genes on chromosomes of related species, as a result of descent from a common ancestor) with vertebrates including our genome as well.Comparison with human genome sequence reveals similarity in both protein coding and non coding regions.Synteny with vertebrates and significant homology with human coding and non coding (regulatory regions) suggests that last common ancestor of all chordates might have a genome sequence similar to Amphioxus irrespective of its morphology.With complete genome sequence published and analysis with various genomes might unearth more clues to our own lost ancestry and also on chordate evolution.
Follow this link in order to read the minute details of this iconic animal genome status in today’s Nature issue,where it occupies the front cover.
Reference:
Nature 453, 1064-1071 (19 June 2008)
The amphioxus genome and the evolution of the chordate karyotype.
Nicholas H. Putnam, Thomas Butts, David E. K. Ferrier, Rebecca F. Furlong, Uffe Hellsten,
Takeshi Kawashima, Marc Robinson-Rechavi, Eiichi Shoguchi, Astrid Terry, Jr-Kai Yu,E lia Benito-Gutie´rrez, Inna Dubchak, Jordi Garcia-Ferna`ndez, Jeremy J. Gibson-Brown1, Igor V. Grigoriev,Amy C. Horton, Pieter J. de Jong, Jerzy Jurka, Vladimir V. Kapitonov, Yuji Kohara, Yoko Kuroki, Erika Lindquist, Susan Lucas, Kazutoyo Osoegawa, Len A. Pennacchio, Asaf A. Salamov, Yutaka Satou, Tatjana Sauka-Spengler, Jeremy Schmutz, Tadasu Shin-, Atsushi Toyoda, Marianne Bronner-Fraser, Asao Fujiyama, Linda Z. Holland, Peter W. H. Holland, Nori Satoh & Daniel S. Rokhsar
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