Meeting Abstract
Hox genes are homeobox transcription factors essential for patterning the primary body axes of cnidarian and bilaterian animals. Genomic evidence from Nematostella vectensis (Anthozoa), Acropora digitifera (Anthozoa), and Hydra magnipapillata (Hydrozoa) has provided initial insights into the Hox complement of the cnidarian-bilaterian ancestor (CBA), but the exact orthology of many of the cnidarian Hox genes remains a mystery. Consequently, very little is understood about the evolution of these genes within Cnidaria or in the stem lineage of Bilateria. To add more resolution to these questions, we have sequenced and assembled new genomes from all of the major cnidarian lineages that currently lack such resources (i.e., Octocorallia, Cerianthidae, Cubozoa, Staurozoa, and Scyphozoa) and analyzed the Hox content of these datasets along with available cnidarian transcriptomes. Our analyses suggest that the CBA possessed several Hox genes that are no longer present in bilaterians. In addition, we found Hox genes present in some cnidarian lineages that were apparently lost in anthozoans and the model hydrozoan Hydra magnipapillata, which may affect hypotheses regarding the origin of Posterior and Central Hox genes. Lastly, we document extensive loss of Hox and Hox-related genes in Medusozoa and Myxozoa. These new results document notable Hox gene losses in lineages marked by major shifts in body plan and life history strategies, and as such, have important implications for a better understanding of the early evolution of animals.
