Comparative analysis of nuclear ribosomal DNA from the moon jelly Aurelia sp.1 (Cnidaria: Scyphozoa) with characterizations of the 18S, 28S genes, and the intergenic spacer (IGS)
Nuclear ribosomal DNAs (rDNA) constitute a multi-gene family with tandemly arranged units linked by an intergenic spacer (IGS). Here we present the complete DNA sequence (7,731 bp) of a single repeat unit of an rDNA sequence from the moon jelly Aurelia sp.1 (Cnidaria: Scypozoa). The tandemly repeated rDNA units consisted of coding and non-coding regions, whose arrangement was 18S rDNA (1,814 bp, 46.2% of GC content)-internal transcribed spacer 1 (ITS1: 272 bp, 39.7%)-5.8S rDNA (158 bp; 50.7%)-ITS2 (278 bp, 51.4%)-28S rDNA (3,606 bp, 49.7%)-IGS (1,603 bp, 45.6%). GC composition in the single unit of rDNA was 47.8%. None of the 5S rDNA was found in the repeat units. Putative structures of a termination transcription signal (poly(T) tract) and promoter-like bi-repeats within the non-coding region were also identified. A block of minisatellites with five repeats was detected within the IGS. Comparative analyses of parsimony and dot plots showed that the IGS was highly informative. The sequence revealed here was the first completion of rDNA from the phylum Cnidaria, using as a model of rDNA for making molecular comparisons of jellyfish members.
KeywordsJellyfish Nuclear rDNA Transcription repeat unit Minisatellite
We would like to thank Drs. Sheikh Raisuddin and Hans-Uwe Dahms for English editing on the manuscript. We are very grateful to Dr. Timothy J. Page and two anonymous reviewers for reading and critical comments. This work was supported by grants of KOSEF NRL (2006) and ETEP (2006) funded to Jae-Seong Lee, and by a grant of KOSEF (2007) funded to Heum Gi Park. Thus work was also supported by a grant from Korea Polar Research Institute (PE08050) funded to Il-Chan Kim.
- Arai, M. N., 1997. Functional biology of Scyphozoa. Chapman & Hall, New York, NY: 300.Google Scholar
- Chen, C. A., D. J. Miller, N. V. Wei, C.-F. Dai & H.-P. Yang, 2000. The ETS/IGS region in a lower animal, the seawhip, Junceella fragilis (Cnidaria: Anthozoa: Octocorallia): compactness, low variation and apparent conservation of a pre-rRNA processing signal with fungi. Zoological Studies 39: 138–143.Google Scholar
- Collins, A. G., P. Schuchert, A. C. Marques, T. Jankowski, M. Medina & B. Schierwater, 2006. Medusozoan phylogeny and character evolution clarified by new large and small subunit rDNA data and an assessment of the utility of phylogenetic mixture models. Systematic Biology 55: 97–115.PubMedCrossRefGoogle Scholar
- Dawson, M. N., A. Sen Gupta & M. H. England, 2005. Coupled biophysical global ocean model and molecular genetic analyses identify multiple introductions of cryptogenic species. Proceedings of the National Academy of Sciences of the United States of America 102: 11968–11973.PubMedCrossRefGoogle Scholar
- Ki, J.-S., D.-S. Hwang, K. Shin, W. D. Yoon, D. Lim, Y. S. Kang, Y. Lee & J. -S. Lee, 2008. Recent moon jelly (Aurelia sp.1) blooms in Korean coastal waters suggest global expansion: examples inferred from mitochondrial COI and nuclear ITS–5.8S rDNA sequences. ICES Journal of Marine Science 65: 443–452.CrossRefGoogle Scholar
- Kramp, P. L., 1961. Synopsis of the medusae of the world. Journal of the Marine Biological Association of the United Kingdom 40: 337–342.Google Scholar
- Mayer, A. G., 1910. Medusae of the World, Vol. 3. The Scyphomedusae. Carnegie Institution of Washington, Washington, DC: 603–630.Google Scholar
- Schlötterer, C., 1998. Ribosomal DNA probes and primers. In Karp, A., P. G. Isaac & D. S. Ingram (eds), Molecular Tools for Screening Biodiversity. Chapman & Hall, London: 267–276.Google Scholar