Characterization of Satellite DNA from Three Marine Dinoflagellates (Dinophyceae): Glenodinium sp. and Two Members of the Toxic Genus, Protogonyaulax

Abstract

Using CsCI-Hoechst dye or CsCI-ethidium bromide gradients, satellite and nuclear DNAs were separated and characterized in three marine dinoflagellates: Glenodinium sp., and two toxic dinoflagellates, Protogonyaulax tamarensis and Protogonyaulax catenella. In all three dinoflagellates, the lowest density fraction, satellite DNA1, hybridized to chloroplast genes derived from terrestrial plants and/or other algae. Dinoflagellate chloroplast DNAs exhibited molecular sizes of 114 to 125 kilobase pairs, which is consistent with plastid sizes determined for other chromophytic algae (120-150 kilobase pairs). Mitochondrial DNA was not resolved from nuclear DNA in this system. Two additional satellite DNAs, satellite DNA2 and satellite DNA3, recovered from P. tamarensis and P. catenella were similar to one another, both within and between species, when characterized by restriction enzyme analysis. These satellites were 85 to 95 kilobase pairs in size, and exhibited restriction fragments that hybridized to yeast nuclear ribosomal RNA genes. Restriction enzyme analyses and DNA hybridization studies of cpDNA document that the two Protogonyaulax isolates are not evolutionarily identical.The Dinophyceae is a group of unicellular, eukaryotic organisms that is composed of photosynthetic, heterotrophic, phagocytic, and saprophytic forms. These algae are second only to diatoms in their contribution to primary production in marine and freshwater ecosystems. In addition, species of photosynthetic dinoflagellates have been identified as the dominant organisms comprising the toxic "red tides" that periodically close shellfish aquaculture facilities on both the East and West Coasts.Dinoflagellates possess unique DNA characteristics. Cells of this taxonomic group frequently contain very high levels (32-200 pg/cell) of DNA packaged into chromosomes that lack classic histone-like proteins. These chromosomes remain condensed throughout cellular interphase (28) and contain an '

The plastid-encoded psbA gene in the dinoflagellate Gonyaulax is not encoded on a minicircle

“…Plastid genomes in general, and curiously enough, the first reports of dinoflagellate plastid genomes (using one species of Glenodinium and two species of Protogonyaulax), generally produce a limited number of gene fragments after restriction enzyme digestion (Boczar et al, 1991). While neither Glenodinium nor Protogonyaulax have been reexamined for the presence of a minicircular plastid genome, our results with digestion of Gonyaulax AT-rich DNA argues for a high complexity DNA sample.…”

Novel plastid gene minicircles in the dinoflagellate Amphidinium operculatum

“…Despite a report in 1991 (Boczar et al, 1991) of a conventional plastid genome in dinoflagellate algae, recent papers have indicated that there is no full-length plastid genome in those species which have been studied in detail (Zhang et al, 1999;Barbrook and Howe, 2000;Barbrook et al, 2001;Hiller, 2001). Instead, genes for many plastid proteins are arranged on small plasmid-like minicircles of 2 -3 kb.…”

Marine algal toxins: Biochemistry, genetics, and molecular biology

“…Again, this question is somewhat difficult to address except for saxitoxins and perhaps brevetoxins. Results from several laboratories indicate a constant composition (Hall 1982;Boyer et al 1987;Cembella et al 1987;Ogata et al 1987), but other studies have found considerable variation in toxin composition with differing growth conditions (Boczar et al 1988;Anderson et al 1990a, b). Similarly, compositional changes in brevetoxin derivatives have been noted in a dinoflagellate at different phases of its growth cycle (Roszell et al 1990).…”

“…Extensive analysis of several saxitoxin-producing strains, including bacteria, cyanobacteria, and dinoflagellates in my laboratory with a variety of techniques failed to identify plasmid DNAs (R. M. McKay and EG.P unpubl.). Similarly, others (S himizu et al 1990b;Boczar et al 1991) failed to detect plasmids that could be involved in saxitoxin synthesis. Although it seems that autonomously replicating plasmids are not accountable for saxitoxin synthesis, it remains a possibility th2.t transposable elements or viral elements carrying the toxin biosynthetic genes have inserted into the chromosome of toxigenic strains and were not detected by the screening protocols used.…”