Hydra genome has been shaped by several factors. This includes transposable element expansion, horizontal gene transfer, trans-splicing, and simplification of gene structure and gene content that parallel the continued parallel simplification of the Hydra life cycle. The genome of Hydra magnipapillata has been sequenced and compared to the genomes of other animals. This includes insight into the evolution of epithelia, contractile tissues, decelopmentally regulated transcription factors, the Spemann-Mangold organizer, pluripotency genes, and the neuromuscular junction.
Characteristics of Genome
- estimated ~20,000 protein-coding gene based on expressed sequence tags, homology and ab initio ene prediction
- transposable elements make up ~57% of the Hydra genome and represent over 500 different families
- addition of short RNA leader sequences to the 5′ ends of mRNAs by trans-splicing ->operons in eukaryotes
- 71 Hydra gene models showed closer relationships to bacterial genes (candidates for horizontal gene transfer)
- 90 transposable elements that were potentially horizontally transferred into the genome
- 51 unique non-tRNA/non-rRNA transcripts that correspond to putative non-coding RNA genes based on 454 sequencing of short transcripts (~17 microRNAs)
- lost emx, eve, fluorescent protein genes, and circadian rhythm genes
- major bilaterian signaling pathways: Wnt, transforming growth factor-beta, Hedgehog, receptor tyrosine kinase, Notch
- the head organizer uses the Wnt signalling pathway to establish positional values along the body column
- mammalian homologues: Myc, Sox2
- genomes encode proteins from bilaterians for genomes that are involved in the establishment oof cell-cell and cell-substrate contacts
Chapman, J. A., E. F. Kirkness, et al. (2010). “The dynamic genome of Hydra.” Nature 464(7288): 592-596.