GENETIC VARIABILITY AND MOLECULAR PHYLOGENY OF DINOPHYSIS SPECIES (DINOPHYCEAE) FROM NORWEGIAN WATERS INFERRED FROM SINGLE CELL ANALYSES OF rDNA¹

Abstract

The objectives of this study were to determine rDNA sequences of the most common Dinophysis species in Scandinavian waters and to resolve their phylogenetic relationships within the genus and to other dinoflagellates. A third aim was to examine the intraspecific variation in D. acuminata and D. norvegica, because these two species are highly variable in both morphology and toxicity. We obtained nucleotide sequences of coding (small subunit [SSU], partial large subunit [LSU], 5.8S) and noncoding (internal transcribed spacer [ITS]1, ITS2) parts of the rRNA operon by PCR amplification of one or two Dinophysis cells isolated from natural water samples. The three photosynthetic species D. acuminata, D. acuta, and D. norvegica differed in only 5 to 8 of 1802 base pairs (bp) within the SSU rRNA gene. The nonphotosynthetic D. rotundata (synonym Phalacroma rotundatum[Claparède et Lachmann] Kofoid et Michener), however, differed in approximately 55 bp compared with the three photosynthetic species. In the D1 and D2 domains of LSU rDNA, the phototrophic species differed among themselves by 3 to 12 of 733 bp, whereas they differed from D. rotundata by more than 100 bp. This supports the distinction between Dinophysis and Phalacroma. In the phylogenetic analyses based on SSU rDNA, all Dinophysis species were grouped into a common clade in which D. rotundata diverged first. The results indicate an early divergence of Dinophysis within the Dinophyta. The LSU phylogenetic analyses, including 4 new and 11 Dinophysis sequences from EMBL, identified two major clades within the phototrophic species. Little or no intraspecific genetic variation was found in the ITS1–ITS2 region of single cells of D. norvegica and D. acuminata from Norway, but the delineation between these two species was not always clear.

Distribution of Dinophysis species and their association with lipophilic phycotoxins in plankton from the Argentine Sea

“…The latter species might be confused with Dinophysis acuta, which is known to occur in Chilean waters (Balech, 2002), but D. acuta is typically larger in size (54-100 mm) and the maximum width is below the mid-line of the cell, which was never the case for the cells found in this study. Records of Dinophysis norvegica cells in this study were almost restricted to the southern and cooler waters, which agrees with its wide distribution in cold-temperate waters of the northern hemisphere, including the Baltic, Norwegian, North and Arctic Seas (Okolodkov and Dodge, 1996;Meyer-Harms and Pollenhe, 1998;Edvardsen et al, 2003;Jansen et al, 2006). Although D. norvegica is known to be frequently toxigenic around the world, our results do not allow a clear association between D. norvegica and particular lipophilic toxins, as this species was always found at lower cell densities than other putatively toxigenic species from the genus in samples that contained toxins.…”

Two different domains of the luciferase gene in the heterotrophic dinoflagellate Noctiluca scintillans occur as two separate genes in photosynthetic species

“…Compared with the domains of the other luciferases, the Noctiluca domain is shorter by Ϸ60 aa at the N terminus, thus lacking three of the four N-terminal histidines present in Lp luciferase, which have been shown to be critical for the regulation of its activity by pH (13). Based on 18S ribosomal DNA analysis (12), Noctiluca is more primitive than any other previously studied bioluminescent dinof lagellate species. A phylogenetic tree of its LCF domain and the individual domains of the other seven luciferases, based on the protein sequences ( Fig.…”

“…Based on 18S ribosomal DNA, the heterotrophic unarmored species Noctiluca scintillans (Ns) is phylogenetically distant (12), but cell extracts also were shown to react with dinoflagellate luciferin to give light. This emission allowed the identification of a luciferase clone whose expressed protein has a very interesting structure.…”

Ribosomal DNA phylogenies and a morphological revision provide the basis for a revised taxonomy of the Prymnesiales (Haptophyta)

“…28S rDNA was amplified as in Edvardsen et al (2003). PCR products were directly sequenced using a solid phase sequencing method with radioisotopes (Chesnick et al, 1997) or cycle-sequenced (Sequi-Therm, BIOZYM) using infra-red-labelled primers and analysed with a LICOR automatic sequencer (MWG, Everbat, Germany).…”

“…Alternatively, purified PCR products were sequenced directly using the DYEnamic ET terminator Cycle sequencing kit (Amersham Biosciences, USA) according to the manufacturer's recommendations. The PCR fragments were then bidirectionally sequenced using the primers as described in Edvardsen et al (2003) on a MEGABACE (Amersham Biosciences, Germany) automatic sequencing device at the Department of Biology, University of Oslo, Norway. Some templates were cloned (LigAtor, R&D Systems, the Netherlands) prior to automatic sequencing.…”