2 September 2004
Evolving simplicity
Vertebrates and Urochordates are evolution's two successful chordate groups. Urochordates have a far simpler anatomy than vertebrates, so that Darwin and Haeckel saw them as primitive links between worms and vertebrates. Hee-Chan Seo et al. have revisited this idea by looking at the regulatory Hox genes in the Urochordate Oikopleura dioica, a tiny tadpole-like marine organism. Hox genes are of interest owing to their central function in regulating embryo developmental and conserved clustering in one genomic location. Strikingly, Oikopleura has lost all central Hox genes, and those that remain have been dispersed in the genome. This extreme picture suggests that Urochordates are not simple because they are primitive, but because they are simplified.
Hox cluster disintegration with persistent
anteroposterior order of expression in Oikopleura dioica
HEE-CHAN SEO, ROLF BRUDVIK EDVARDSEN, ANNE DORTHEA
MAELAND, MARIANNE BJORDAL, MARIT FLO JENSEN, ANETTE HANSEN, METTE FLAAT,
JEAN WEISSENBACH, HANS LEHRACH, PATRICK WINCKER, RICHARD REINHARDT &
DANIEL CHOURROUT
Nature 431, 67–71 (2004); doi:10.1038/nature02709
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Evolutionary biology: Time, space and genomes
NIPAM H. PATEL
In most animals, the Hox genes — which control development —
are clustered together. But why? New evidence supports the idea that the
requirement for a temporal order of expression keeps the cluster intact.
Nature 431, 28–29 (2004); doi:10.1038/431028a
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