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Dinoflagellate 17S rRNA sequence inferred from the gene sequence: Evolutionary implications
1Laboratoire Arago, Paris VI University, Centre National de la Recherche Scientifique UA 117, 66650 Banyuls sur Mer, France.
Summary
We sequenced the dinoflagellate Prorocentrum micans 17S ribosomal RNA (rRNA), revealing eukaryotic and archaeobacterial features. This suggests dinoflagellates diverged early in eukaryotic evolution.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Genomics
Background:
- Dinoflagellates are a diverse group of eukaryotic microorganisms with unique biological characteristics.
- Understanding their evolutionary position is crucial for reconstructing early eukaryotic diversification.
- Ribosomal RNA (rRNA) sequences are valuable markers for phylogenetic analysis.
Purpose of the Study:
- To determine the complete nuclear-encoded small-ribosomal-subunit RNA (17S rRNA) gene sequence of the dinoflagellate Prorocentrum micans.
- To analyze the secondary structure of P. micans 17S rRNA.
- To compare the P. micans 17S rRNA sequence with those from other eukaryotic and prokaryotic organisms to infer evolutionary relationships.
Main Methods:
- Cloning and sequencing of the nuclear-encoded 17S rRNA gene from Prorocentrum micans.
- Bioinformatic analysis to determine the sequence length and gene copy number.
- Secondary structure modeling of the 17S rRNA.
- Comparative sequence analysis with homologous rRNA from diverse taxa (e.g., Xenopus laevis, Saccharomyces cerevisiae, Zea mays, Dictyostelium discoideum, Halobacterium volcanii).
Main Results:
- The complete 17S rRNA sequence of Prorocentrum micans, comprising 1798 nucleotides, was determined.
- The 17S rRNA genes exist as a family of approximately 200 tandemly repeated units per haploid genome.
- A tentative secondary structure model for P. micans 17S rRNA was proposed.
- Comparative analysis revealed that while the dinoflagellate 17S rRNA exhibits most eukaryotic structural features, it also possesses archaeobacterial-like structural elements.
Conclusions:
- The 17S rRNA sequence and secondary structure of Prorocentrum micans provide insights into dinoflagellate molecular evolution.
- The presence of archaeobacterial-like features supports the hypothesis that dinoflagellates represent an early-branching lineage within eukaryotes.
- This study reinforces the view of dinoflagellates occupying a basal position in the eukaryotic tree of life.
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