Cell cycle network evolution in a fungal ancestor was punctuated by the arrival of a viral DNA-binding protein that was permanently incorporated into the regulatory network controlling cell cycle entry.
Sponges and ctenophores lack hypoxia-inducible factors, suggesting that the metazoan last common ancestor could have lived aerobically under severe hypoxia and did not need to regulate its transcription in response to oxygen availability.
Protein coding genes strongly support a sister group relationship between Placozoa and Cnidaria to the exclusion of Bilateria, contradicting previous phylogenies, which have likely been misled by pervasive compositional heterogeneity.
Functional recapitulation of a likely evolutionary gain in gene expression shows that two genes are sufficient to switch mesoderm cell internalization from stochastic cell ingression to coordinated epithelial invagination.
The foundations of genomic complexity in multicellular animals have deep roots in their unicellular prehistory, both in terms of innovations in gene content, as well as the evolutionary dynamics of genome architecture.