Ecological Role of Purple Sea Urchins
in a minor fraction of genes account for the adaptive differences that separate diverging species. If we had the sequence of several additional closely related sea urchin genomes, this model could be directly assessed. Another opportunity would arise if the genome sequences of two other widely used sea urchin species, Lytechinus variegatus and Paracentrotus lividus, were available: Comparison with the genome of S. purpuratus would yield a global map of conserved regulatory modules around every
... ene. Finally and most essentially, comparative regulatory genomics provides the key to unlock the basic processes of evolution. It has been possible to compare on a small scale the embryonic networks of two animals that have evolved independently for half a billion years, the sea urchin and the sea star (6). The comparison revealed both a shocking degree of architectural conservation in certain subcircuits and a shocking level of change of others. This cuts close to the bone of the evolutionary processes by which body plans have diverged in evolution (7) . Large-scale comparisons of regulatory gene networks between multiple species of different degrees of relatedness will provide a new dimension to our understanding of evolutionary mechanism and of network architecture and system design. The sea urchin genome sequence did not open the door to a new pathway to knowledge; it opened the door to a nexus of such pathways. They lead in diverse directions, but their central and unifying reference is the genome sequence. Indeed, its central foundation in genomics will characterize a large area of bioscience, a reorganization that is already upon us, the coalescence of what might be called "informational bioscience." This will consist of a scientific continuum over what used to be the distinct disciplines of regulation molecular bi-ology, evolution, developmental biology, and genomics, together with their mathematical and computational support and more traditional descriptive knowledge. The sea urchin research community is now experiencing this intellectual revolution.