Before revision: In yeast, phenotypic adaptations can evolve by natural selection of conformational variant prions and their variant amyloid fibers. This system requires the Hsp104 disaggregase, which fragments amyloid fibers into smaller seed prions that are passed on to mitotic descendants and meiotic spores. Interestingly, Hsp104 is found in diverse eukaryotes except metazoans. To investigate whether a prion-based transmission "genetics" was incompatible with the evolution of Metazoa , we identify genes conserved in fungi and choanoflagellates but lost in animals.
After revision: The evolution of animals involved a transition from a unicellular transcriptional regime to one supporting developmentally programmed somatic multicellularity. This transition was facilitated by an emergent developmental gene repertoire via gene family expansion and new gene innovation. Unknown, however, is whether this genomic-rewiring was constrained by genetic functions incompatible with key features of animals. Here , we identify genes conserved in fungi and choanoflagellates but lost in animals.