Meeting Abstract
Cnidarians are well-positioned to answer key questions about the evolutionary and functional biology of animals, as they are the sister group to the bilaterians. We have chosen to focus on the colonial cnidarian Hydractinia, a hydrozoan that forms colonies of polyps interconnected through a stolonal network. Hydractinia has lost the medusa stage and produces gametes directly from polyps known as gonozooids. Hydractinia displays remarkable traits, such as the ability to regenerate all tissues throughout its life from pluripotent stem cells (called ‘i-cells’) and the ability to recognize self from non-self via cell-cell contact, a phenomenon called allorecognition. Hydractinia is easy to culture, spawns daily, and is amenable to transgenesis and gene knockdown studies. We have sequenced and generated preliminary assemblies for the genomes of H. echinata and its sister species, H. symbiolongicarpus, based on PacBio and Illumina sequence data at high coverage. Similar to Hydra, the genomes are AT-rich (65%) and highly repetitive (47%). We have assembled transcriptomes for both species and performed shotgun proteomics on H. echinata as a first step towards comprehensive annotation of the genomes. We are using a comparative genomics approach to assess their genomes in relation to other model species and are characterizing genes, small RNAs, methylation status, and repeat content. With complete, high-quality genomic data, these Hydractinia species are emerging as robust models for developmental, evolutionary, and stem cell biology.
