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On the evolution of bilaterality.

Grigory Genikhovich1, Ulrich Technau1

  • 1Department for Molecular Evolution and Development, Centre of Organismal Systems Biology, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria grigory.genikhovich@univie.ac.at ulrich.technau@univie.ac.at.

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Bilaterality, the defining trait of animals with two body axes, evolved early in animal development. This study investigates its evolutionary origins by comparing gene expression in radially and bilaterally symmetric animals.

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Area of Science:

  • Evolutionary developmental biology
  • Comparative genomics
  • Animal body plan evolution

Background:

  • Bilaterality, characterized by two orthogonal body axes, is fundamental to animal development and complexity.
  • The evolutionary origin of bilaterality, whether a single event or multiple independent events, remains a key question.
  • Cnidaria, as the sister group to Bilateria, offer crucial insights into the early evolution of body axes.

Purpose of the Study:

  • To compare the molecular mechanisms controlling body axes in radially and bilaterally symmetric organisms.
  • To identify the conserved genetic toolkit essential for establishing bilaterality.
  • To evaluate the monophyletic or polyphyletic origin of bilaterality in animals.

Main Methods:

  • Comparative analysis of gene expression patterns in cnidarians and bilaterians.
  • Identification of conserved developmental genes and pathways.
  • Phylogenetic analysis to infer the evolutionary history of bilaterality.

Main Results:

  • Identified conserved molecular pathways governing body axis formation across diverse animal groups.
  • Characterized a minimal set of genetic traits likely ancestral to Bilateria.
  • Provided evidence supporting a specific evolutionary scenario for the origin of bilaterality.

Conclusions:

  • The evolution of bilaterality involved the co-option and refinement of pre-existing genetic toolkits.
  • Understanding conserved developmental mechanisms sheds light on major evolutionary transitions.
  • Comparative studies in sister groups like Cnidaria are vital for reconstructing ancestral states.