Bioinformatický seminár

Tue 27 Mar. 2012, 17:20

Title: Domazet-Loso, Tautz (2010) A phylogenetically based transcriptome age index mirrors ontogenetic divergence patterns
Speaker: Katka Juríková

Parallels between phylogeny and ontogeny have been discussed for almost
two centuries, and a number of theories have been proposed to explain such
patterns. Especially elusive is the phylotypic stage, a phase during
development where species within a phylum are particularly similar to each
other. Although this has formerly been interpreted as a recapitulation of
phylogeny, it is now thought to reflect an ontogenetic progression phase,
where strong constraints on developmental regulation and gene interactions
exist. Several studies have shown that genes expressed during this stage
evolve at a slower rate, but it has so far not been possible to derive an
unequivocal molecular signature associated with this stage. Here we use a
combination of phylostratigraphy and stage-specific gene expression data
to generate a cumulative index that reflects the evolutionary age of the
transcriptome at given ontogenetic stages. Using zebrafish ontogeny and
adult development as a model, we find that the phylotypic stage does
indeed express the oldest transcriptome set and that younger sets are
expressed during early and late development, thus faithfully mirroring the
hourglass model of morphological divergence. Reproductively active animals
show the youngest transcriptome, with major differences between males and
females. Notably, ageing animals express increasingly older genes.
Comparisons with similar data sets from flies and nematodes show that this
pattern occurs across phyla. Our results indicate that an old
transcriptome marks the phylotypic phase and that phylogenetic differences
at other ontogenetic stages correlate with the expression of newly evolved