The transition to the aggregative stage of Capsaspora owczarzaki, a close unicellular relative to Metazoa, is associated with significant upregulation of orthologs of genes that are important for multicellularity in metazoans.
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.
A genetic screen reveals that two predicted glycosyltransferases promote rosette development and prevent cell clumping in one of the closest living relatives of animals, the choanoflagellate S. rosetta.
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.
The complex chromatin-based genomic regulatory system controlling developmental gene expression in complex bilaterians predates the evolution of morphological complexity and may have been a prerequisite for the evolution of the first simple multicellular animals.