Seminar with Prof Bernard Degnan

Reconstruction of the ancestral metazoan genome: structural and functional aspects of the sponge genome

Speaker: Prof Bernard Degnan, University of Queensland
Time: 11.00am
Date:  Thursday 25 May 2006
Venue: 78-622/621
Host: Prof Janet Wiles
Abstract:

  One of the most significant evolutionary events on Earth is the
  evolution of multicellular animals from a simple protist.  This
  major transition required a range of innovations, many of which
  still can be seen in extant animals. Any meaningful reconstruction
  of the last common ancestor (LCA) to all living metazoans through
  comparative analyses of extant taxa requires input from the most
  ancient body plans (i.e. phyla), of which Porifera is arguably the
  oldest. By comparing sponge, cnidarian and bilaterian genomes and
  development, I will show that this ancestor was far more complex
  than broadly appreciated. Specifically, I infer from comparing the
  genome of the demosponge Reniera with eumetazoan genomes that the
  LCA possessed nearly all developmental gene families used by living
  animals and that these families evolved before metazoan
  cladogenesis. Based on the observation that most of these gene
  families are markedly smaller in Reniera, I infer that there has
  been extensive gene duplication and divergence in the eumetazoan
  lineage after it split from the poriferan lineage. Analysis of the
  developmental expression of some of these genes in Reniera strongly
  suggests that the LCA had already evolved a sophisticated regulatory
  network for specifying cells, allocating them into specific cell
  layers and patterning them along embryonic axes.


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