Draft assembly of the symbiodinium minutum nuclear genome reveals dinoflagellate gene structure

Eiichi Shoguchi, Chuya Shinzato, Takeshi Kawashima, Fuki Gyoja, Sutada Mungpakdee, Ryo Koyanagi, Takeshi Takeuchi, Kanako Hisata, Makiko Tanaka, Mayuki Fujiwara, Mayuko Hamada, Azadeh Seidi, Manabu Fujie, Takeshi Usami, Hiroki Goto, Shinichi Yamasaki, Nana Arakaki, Yutaka Suzuki, Sumio Sugano, Atsushi ToyodaYoko Kuroki, Asao Fujiyama, Mónica Medina, Mary Alice Coffroth, Debashish Bhattacharya, Nori Satoh

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Abstract

Background Dinoflagellates are known for their capacity to form harmful blooms (e.g., "red tides") and as symbiotic, photosynthetic partners for corals. These unicellular eukaryotes have permanently condensed, liquid-crystalline chromosomes and immense nuclear genome sizes, often several times the size of the human genome. Here we describe the first draft assembly of a dinoflagellate nuclear genome, providing insights into its genome organization and gene inventory. Results Sequencing reads from Symbiodinium minutum were assembled into 616 Mbp gene-rich DNA regions that represented roughly half of the estimated 1,500 Mbp genome of this species. The assembly encoded ∼42,000 protein-coding genes, consistent with previous dinoflagellate gene number estimates using transcriptomic data. The Symbiodinium genome contains duplicated genes for regulator of chromosome condensation proteins, nearly one-third of which have eukaryotic orthologs, whereas the remainder have most likely been acquired through bacterial horizontal gene transfers. Symbiodinium genes are enriched in spliceosomal introns (mean = 18.6 introns/gene). Donor and acceptor splice sites are unique, with 5′ sites utilizing not only GT but also GC and GA, whereas at 3′ sites, a conserved G is present after AG. All spliceosomal snRNA genes (U1-U6) are clustered in the genome. Surprisingly, the Symbiodinium genome displays unidirectionally aligned genes throughout the genome, forming a cluster-like gene arrangement. Conclusions We show here that a dinoflagellate genome exhibits unique and divergent characteristics when compared to those of other eukaryotes. Our data elucidate the organization and gene inventory of dinoflagellates and lay the foundation for future studies of this remarkable group of eukaryotes.

Original languageEnglish (US)
Pages (from-to)1399-1408
Number of pages10
JournalCurrent Biology
Volume23
Issue number15
DOIs
StatePublished - Aug 5 2013

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All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

Cite this

Shoguchi, E., Shinzato, C., Kawashima, T., Gyoja, F., Mungpakdee, S., Koyanagi, R., Takeuchi, T., Hisata, K., Tanaka, M., Fujiwara, M., Hamada, M., Seidi, A., Fujie, M., Usami, T., Goto, H., Yamasaki, S., Arakaki, N., Suzuki, Y., Sugano, S., ... Satoh, N. (2013). Draft assembly of the symbiodinium minutum nuclear genome reveals dinoflagellate gene structure. Current Biology, 23(15), 1399-1408. https://doi.org/10.1016/j.cub.2013.05.062