Emerging principles of regulatory evolution
Benjamin Prud'homme * , † , Nicolas Gompel † , ‡ , and
Sean B. Carroll * , §
*Howard Hughes Medical Institute and University of Wisconsin, Bock Laboratories, 1525 Linden Drive, Madison, WI 53706; and
‡Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom
Understanding the genetic and molecular mechanisms governing the evolution of morphology is a major challenge in biology. Because most animals share a conserved repertoire of body-building and -patterning genes, morphological diversity appears to evolve primarily through changes in the deployment of these genes during development. The complex expression patterns of developmentally regulated genes are typically controlled by numerous independent cis-regulatory elements (CREs). It has been proposed that morphological evolution relies predominantly on changes in the architecture of gene regulatory networks and in particular on functional changes within CREs. Here, we discuss recent experimental studies that support this hypothesis and reveal some unanticipated features of how regulatory evolution occurs. From this growing body of evidence, we identify three key operating principles underlying regulatory evolution, that is, how regulatory evolution: (i) uses available genetic components in the form of preexisting and active transcription factors and CREs to generate novelty; (ii) minimizes the penalty to overall fitness by introducing discrete changes in gene expression; and (iii) allows interactions to arise among any transcription factor and downstream CRE. These principles endow regulatory evolution with a vast creative potential that accounts for both relatively modest morphological differences among closely related species and more profound anatomical divergences among groups at higher taxonomical levels.
pleiotropy, cis-regulation, transcription, pigmentation, body plan
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Author contributions: B.P., N.G., and S.B.C. wrote the paper.
†Present address: Institut de Biologie du Développement de Marseille-Luminy, Unité Mixte de Recherche, Centre Nationale de la Recherche Scientifique 6216, Case 907, Parc Scientifique de Luminy, 13288 Marseille Cedex 9, France.
This paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “In the Light of Evolution I: Adaptation and Complex Design,” held December 1–2, 2006, at the Arnold and Mabel Beckman Center of the National Academies of Sciences and Engineering in Irvine, CA. The complete program is available on the NAS web site at www.nasonline.org/adaptation_and_complex_design.
The authors declare no conflict of interest.
© 2007 by The National Academy of Sciences of the USA