RFX TF-mediated transcription and the origin of metazoans. The common ancestor of metazoans, choanoflagellates, and fungi was likely a ciliated unicellular eukaryote with a single RFX TF. Over the course of evolution, some fungi lost RFX TFs while preserving cilia, some lost cilia but kept RFX, and some lost both. Only a few fungi kept both cilia and RFX. The last common ancestor (LCA) of Monosiga and metazoans preserved both cilia and RFX.