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.